Handbook p6 heat

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Agastya International Foundation

Heat Handbook P6

‘’Whoever teaches learns in the act of teaching, and whoever learns teaches in the act of learning. ’’ -Paulo Freire, 1921-1997 From The Pedagogy of Freedom [Type text]

1

Handbook P6 Heat OVERVIEW OF HANDBOOK ABL

CONCEPT

NO OF ACTIVITIES

TIME (min)

PAGE NO

ABL 1

Heat – Introduction and Sources

3

55

4

ABL 2

Temperature

3

55

15

ABL 3

Effect of heat

3

60

27

ABL 4

Effect of heat on Dimension

5

65

38

ABL 5

Change of State

2

35

54

ABL 6

Conduction of heat

3

40

61

ABL 7

Convection of heat

4

55

72

ABL 8

Radiation of heat

2

40

82

ABL 9

Methods of Mixtures

1

60

88

ABLs WITH REFERENCE TO STANDARD

S.No. 1 2 3 4 5

STANDARD 6, 7 6, 7, 8 7, 8, 9 7, 8, 9 9, 10

RELEVANT ABL ABL 1 ABL 2 ABL 3 ABL 4 ABL 5

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2

LIST OF FIGURES, CHARTS AND WORKSHEETS

S. No

Name

Page No

Figure 1

Heating Set-up for beaker with wire gauge, spirit lamp and tripod stand

6

Figure 2

Figure 2: Types of thermometers

17

Figure 3

Figure 3 - Anders celcius

20

Figure 4

Figure 4 - Heating setup

22

Figure 5

Figure 5: Heating arrangement for beaker with wire gauge, spirit lamp and tripod stand

31

Figure 6

Figure 6: Experimental Arrangement to measure heat

33

Figure 7

Figure 7 -Linear Expansion Model

39

Figure 8

Figure 8 – Ball and Ring Model

40

Figure 9

Figure 9: Iron box

44

Figure 10

Figure 10: Experimental arrangement for effect of heat on volume of Liquids

46

Figure 11

Figure 11: Effect of heat on volume of gases

52

Figure 12

Figure 12 – Hot air balloon

53

Figure 13

Figure 13 – Conduction along a rod

67

Figure 14

Figure 14 – Experimental setup for convection

74

Figure 15

Figure 15 – Convection model 1

80

Figure 16

Figure 16 – Convection model 2

80

Figure 17

Figure 17 - Radiometer

83

Figure 18

Figure 18: Radiation experiment

85

Chart 1

Chart 1 - Part of a thermometer

18

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3

Worksheet 1

Students observation sheet 1

94

Worksheet 2

Students observation sheet 2

95

Worksheet 3

Students observation sheet 3

96

Note to Instructor: All the figures in this handbook are for the Instructor’s reference only. The Charts need to be printed and shown to the learners during the course of the activity. Worksheets need to be printed out in advance for the learners. The number of worksheets required is mentioned in the Material List.

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4

ABL 1 Heat – Introduction and Sources Activity

Learning objective

Key messages

Time (min)

1.1

How do we feel when we



touch things?



Objects can feel very hot, very cold or anything in between.

The hotness of an object can be felt by us through our skin.

15

What do we mean by the feeling of cold and hot?

1.2

What is heat?

1.3

What are the sources of heat apart from fire?



Heat is a form of energy can that be exchanged between a body and its surroundings.  Heat can be measured in Calories or Joules.  There are several sources of heat – sun, fuels, friction, electric heater, few chemical reactions.

TOTAL

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10

20

55

5

ABL 1.1

Time: 15mins

LEARNING OBJECTIVE– How do we feel when we touch things? What do we mean by the feeling of cold and hot?

Note to Instructor –The purpose of this activity is to introduce the concept of heat in a manner in which the children are familiar – feeling objects as ‘hot’ or ‘cold’

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beakers (250 ml, Borosil)

3 per class

2

Tripod Stand

1 per class

3

Wire gauge

1 per class

4

Spirit lamp

1 per class

5

Match box

1 per class

6

Dust bin with sand or water

1 per class

(to dispose burnt matches) 7

Tap water

8

Observation sheet 1 –

500ml 40 per class

Worksheet 1

Things to do Print as many copies of Observation sheet 1 (attached at the end of the handbook) as there are students.

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Do these 10 minutes before the class 1. Label the three beakers as A, B and C. 2. Fill the three beakers halfway with water.

3. Arrange the heating setup on a table, as shown in Figure 1.

4. Heat the water in beaker A using the spirit lamp for a few minutes.

5. The water should be hot enough to feel the heat by dipping a finger. Make sure it does not cool down before the learners arrive.

6. Place beaker B in shade.

7. The water in beaker C should be cooler than beaker B. You can cool Figure 1 : Heating Set-up for beaker with wire gauge, spirit the water by placing the beaker under a fan or by wrapping in a wet cloth. lamp and tripod stand 8. Place the three beakers in a row on a table. Make sure they do not touch each other.

Safety Precautions Be careful that the water in Beaker A is not too hot and burn fingers. It is enough if it is warm.

SESSION Link to known information/previous activity Not Applicable Procedure (Individual Activity) Distribute observation sheet 1 to all the learners.

Ask the learners to form a line and one by one, each of them should dip their finger in three beakers A, B, and C, in sequence.

Ask the learners to return back to their seats and write observations in Column 1 of Observation sheet 1.

UNDERSTANDING THE ACTIVITY Leading questions 1. What are the similarities between the three beakers?

2. What are the differences between the three beakers?

3. Does your day-to-day drinking water feel similar to the water in beaker A, B or C? Discussion and Explanation Discussion Item 1: The following points are about how some objects feel hot, some feel cold, and some feel neither hot, nor cold. The hotness of an object can be felt by us (through our skin). It cannot be seen or smelt by us.

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

The three beakers are similar in the following ways:  They are made of the same material – glass  They are of the same size  They have the same graduation scale marked on them  They are filled with the same quantity of water  Overall, they are similar in appearance  The three beakers are different in the way the water felt – Beaker A felt hot/warm. Beaker B felt warm/normal. Beaker C felt normal/cold The hotness or coldness of an object can be felt by us, but not seen or smelt.

We use words like hot, warm, lukewarm, cold, cool and normal to describe how cold/hot objects feel.

1. The water we drink everyday could be either warm, or normal or cold.

When we touch some objects we feel cold because our body loses some heat to the object.

When we touch some objects we feel hot because, heat flows from the object into our body.

KEY MESSAGES  

Objects can feel very hot, very cold or anything in between.

The hotness of an object can be felt by us through our skin.

LEARNING CHECK Can you tell if a glass of water feels normal or warm without touching it?

(Answer: No)

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ABL 1.2

Time: 10 min

LEARNING OBJECTIVE – What is heat?

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker (250 ml, Borosil)

1 per class

2

Tripod stand

1 per class

3

Spirit lamp

1 per class

4

Wire gauge

1 per class

5

Water

6

Dustbin with sand/water

250ml 1 per class

Things to do 1. Arrange the heating setup on a table, as shown in Figure 1. Do not light the spirit lamp.

2. Fill the beaker 3/4th with water and place it on the wire gauge.

Safety Precautions Make sure the spirit lamp is not lit, and the water is at normal temperature

SESSION Link to known information/previous activity We learnt that some objects can feel hot and some can feel cold. Here we will see how we can make objects become hotter or colder Procedure (Demonstration) Pick one learner and ask him/her to come on the table where the heating set-up is placed.

Ask the learner to dip his/her finger in the beaker containing water. Make sure that the finger does not touch the base of the beaker.

After the learner’s finger is in the water, ignite the spirit lamp. Ask the learner to tell you when he/she starts feeling that the water is warm. Heat the water until the learner tells that the water is getting warm.

Make sure that you do not heat for more than a few seconds.

Turn off the spirit lamp.

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Safety Precautions Ensure that the learner’s fingers do not touch the base of the beaker.

Ensure you do not let the water become too hot.

UNDERSTANDING THE ACTIVITY Leading questions 1.

2.

3.

4.

5.

6.

How did the water feel before igniting the spirit lamp?

How do you think the spirit lamp’s flame would feel compared to the water?

How did the water feel after igniting the spirit lamp? Why? What did the fire in the spirit lamp do to the water?

What would have happened if we had continued heating for long?

How did the water feel when the spirit lamp was turned off? Ten minutes from now, how would the water feel?

7. Why do we feel cold when we touch ice?

Discussion and explanation Discussion Item 1: The following points are about how the water got heated due to the flame (fire) of the spirit lamp and starts cooling down once the spirit lamp is turned off. Introduce the concept of heat and energy here. Heat is the flow of energy from the lamp’s fire to the water; and when the lamp was turned off, heat flows from the water to the air around the water           

The water felt normal before igniting the spirit lamp.

The spirit lamp’s flame is very hot and will burn the finger if we touch it.

Once the spirit lamp is lit, the water slowly starts becoming hot.

This is because heat energy flows from the hot flame to the normal water, making the water hot.

We have all heard of the word “energy”. Heat is the form of energy that flows between hot and cold objects.

When we turned off the spirit lamp, the water started cooling down. Where does the heat in that water go? The air surrounding the water is cooler than the water. So heat flows from the water to the air. As a result the water and beaker cool down.

If heat is being added to the air, we can expect it to be warmer. However, since the air around the beaker is vast, it did not become hot enough for us to feel the heat.

After ten minutes, the water would feel normal, since all the heat energy would have flown from the water to the surrounding air.

We observed that the heat flowed from the flame to the water and from the water to the air around it.

So heat energy always flows from hotter to colder objects.

We all know that our body is warmer than ice. So when we touch ice, heat will flow from our bodies to the ice (because heat always flows from hotter to colder objects).

Discussion Item 2: The following points are about the units of measurement of heat.

Heat is often measured in “Calories”.

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1 Calorie is the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius.

We discussed that heat is a form of energy. The SI unit of Energy is Joule. 1 calorie = 4.18 joules.

KEY MESSAGES  

Heat is a form of energy can that be exchanged between a body and its surroundings.

Heat can be measured in Calories or Joules

LEARNING CHECK When you put an ice cube in a glass of water, what happens to the water, the glass and the ice?

Why? (Answer for Instructor’s reference: since Ice is colder than water heat flows water to ice, water thus becomes cooler and ice begins to melt, the glass wall in turn loses heat to water and gets cooler.

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11

ABL 1.3

Time: 20 min

LEARNING OBJECTIVE – What are the sources of heat apart from fire?

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Drinking water

Sufficient for all learners

Things to do Not Applicable Safety Precautions Not Applicable

SESSION SESSION 1.3a Note to Instructor: Perform only on sunny days. Skip activity on cloudy/ rainy days Link to known information/previous activity In activity 1.2, fire in the spirit lamp was the source of heat. Here we will learn about the other sources of heat.

Procedure (Individual Activity) Take the learners outdoors and ask them to stand in the sun for 3 to 4 minutes. Bring them back to the class and give everyone drinking water.

UNDERSTANDING THE ACTIVITY 1.3a Leading questions 1. How did you feel while standing in the sun? Why did you feel so?

2. What is common between the previous activity, where we heated water in a beaker for a few seconds; and standing in the sun for a few minutes?

3. What are the sources of heat we have seen today?

Discussion and explanation Discussion Item 1:  Standing in the sun felt hot. This is because heat is transferred from the solar radiation to our body.  In the previous activity, heat flows from the flame to the water. Here heat flows from the sun to us.

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

A large amount of heat energy on earth is obtained from the burning of wood, coal, L.P.G and other fuels. The fuel in the spirit lamp is a volatile liquid fuel. (In case you used a Bunsen burner instead of the lamp, the fuel is a gas).

SESSION 1.3b Procedure (Individual Activity) Ask the learners to fill column 2 of observation sheet 1. Give them 1-2 minutes.

While they are filling the sheet, make two columns on the board – Hot objects and Cold objects.

After they have finished writing, randomly pick one learner. Ask the learner to read column 2 of his/her observation sheet.

When the learner is reading his/her answers, write the answers on the board under the Hot objects and Cold objects headings. Ask the other learners to put a tick next to their answers if they are same as the objects on the board.

Give opportunities to around 5-6 learners to tell their answers which are not yet on the board. As they tell, keep adding the words to the board.

UNDERSTANDING THE ACTIVITY 1.3b Leading questions 1. What made the water in beaker A, or the tea, coffee, rice (objects listed on the board under Hot objects) hot?

2. What made the water in beaker C, or the juice, ice cream (objects listed on the board under Cold objects) cold?

3. Do all hot objects on the board feel the same? Do all cold objects on the board feel the same?

Discussion and Explanation Discussion Item 1: The following points are about how objects get heated or cooled, and the children should think about the sources of heat 



Objects become hot in several ways  The sun can make objects hot  Electricity can make objects hot. Example, electric iron (for ironing clothes), room heater, light bulb.  Burning gas can produce a fire, which can heat objects. This is how our kitchen stoves work.  Kerosene is used to light the lamps, and petrol is used to run engines.

Objects are cooled in several ways. Some are:  Electricity can cool objects through refrigerators and AC (Air conditioner)

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

 Cold weather can cool objects  In both cases, some external source is required to heat or cool objects The natural weather can heat or cool objects All hot objects do not feel the same. Similarly, all cold objects do not feel the same. A frying pan on a stove is very hot. Fire is very hot. A cup of tea may not be as hot as the fire. Frozen ice is much colder than a bottle of juice taken from the refrigerator.

SESSION 1.3c Link to known information/previous activity NA Procedure (Individual Activity) Ask the learners to rub their hands together for a few seconds.

UNDERSTANDING THE ACTIVITY 1.3c Leading questions 1. How does your hand feel?

2. What is the source of heat?

Discussion and explanation Discussion Item 1:  

The hands become warm. Rubbing between two surfaces can also produce heat. Here, there is no hotter source of heat (from where heat is flowing to us), unlike the previous examples we have seen.

We know that heat is a form of energy. When we rub our hands together, the movement of our palms against each other produces heat energy (due to friction); the energy that we lose in rubbing is converted into heat energy.

KEY MESSAGES 

There are several sources of heat – sun, fuels, friction, and electric heater, few chemical reactions.

LEARNING CHECK If a glass of water is kept in this room, can it become hot on its own?

(Answer for Instructor’s reference: No, the water cannot become hot on its own, it needs some source of energy to heat it)

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TRY IT YOURSELF The next time you see something warm to drink or eat at home, try this. Take an ice cube from the fridge.

Keep the ice cube in your right hand and touch the warm vessel/cup with your left hand. After a few seconds, place both your palms together and feel the heat flowing from the hot hand to the cold hand.

INTERESTING INFORMATION Do you know how woolen clothes keep us warm?

Some materials such as metals are good conductors of heat. This means they are good at transferring heat.

That is why most cooking vessels are made of metal. Materials such as wool and air are bad conductors of heat. Wool traps air in its fibers and both wool and air do not allow heat in our body to escape to the cool environment. That is why we feel warm when we wear woolen clothes.

WEB RESOURCES http://scienceforkids.kidipede.com/chemistry/atoms/heat.htm http://www.youtube.com/watch?v=bgbbMK-jkH8

VOCABULARY Heat: A form of energy that flows from a hotter to a colder object Friction: A resistance encountered when one body moves relative to another body with which it is in contact Joule: Joule is a unit of energy or work done. It is equal to the work done by a force of 1 Newton acting through a distance of one meter.

Calorie: Calorie is a unit of heat. It is the amount of heat required to raise the temperature of 1 gram of water by 1 °C at 1 atmospheric pressure.

REFERENCES http://www.raystoreylighting.com/chem/chem_2.htm

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15

ABL 2 - Temperature Activity

Learning objective

Key messages

Time (min)

2.1

What is temperature?



2.2

Measurement of



temperature –  Thermometer

2.3

a) How to use a



thermometer?  b) Kinds of

Temperature is a measure of the 5 degree of hotness or coldness of an object or environment.

Thermometers work on the 15 principle that liquids expand when heated.

The quantum of expansion of the liquid is a measure of change in temperature Depending on the purpose of the thermometer, it can have a different temperature range.

There are three temperature scales – degree Celsius, degree Fahrenheit and Kelvin

45

thermometers in use Total

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16

ABL 2.1

Time: 5 min

LEARNING OBJECTIVE – What is temperature?

ADVANCE PREPARATION Material List Not Applicable Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity So far we have seen how objects become hot or cold and we have come across objects of various degree of hotness. Here we will introduce a physical quantity that measures the degree of hotness.

Procedure (Group Discussion) This is a discussion activity. Directly ask the leading questions.

UNDERSTANDING THE ACTIVITY Leading questions 1.

2.

3.

4.

5.

6.

How do you tell if an object is heavy or light?

How do you tell if a car is fast or slow?

Can you measure the heat in an object?

Have you heard the word ‘temperature’ before?

If you visit a doctor when you have fever, does he say anything about your ‘temperature’?

While giving the weather forecast in the news, what do they say about the temperature of a place?

Discussion and Explanation The following points are about how temperature is a measure of degree of hotness.  We can tell how heavy or light an object is by measuring its weight.  The speed of a car indicates how fast or slow it is.  Similarly, we can tell how hot or cold an object is by measuring its temperature.  Temperature is the degree of hotness of an object or environment.  When people have fever, the doctor says that their temperature is high – maybe 40 degrees Celsius.  In the news, during the weather forecast, they might say that the weather is very cold when the temperature is 5 degrees Celsius and very hot when the temperature is 40 degrees Celsius.

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The sun has a very high temperature

KEY MESSAGES 

Temperature is a measure of the degree of hotness or coldness of an object or environment.

LEARNING CHECK Does this table/chair have a temperature?

(Answer for Instructor’s reference: Yes, every object has a temperature, since temperature is just a measurement of how hot or cold an object is)

Time: 15 min

ABL 2.2

LEARNING OBJECTIVE – Measurement of temperature- Thermometer Note to Instructor–This activity is to get the learners to understand how the thermometer is designed.

ADVANCE PREPARATION Material List Note to Instructor: It is not necessary to use all the types of thermometers mentioned below. Try to get at least two types of thermometer. Try to get at least a Clinical Thermometer, since it is likely that they might have it at home and it would be useful to learn how to read it.

Figure 2: Types of thermometers

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S.NO

Material

Required Quantity

1

Laboratory Thermometer

1 per class

2

Clinical Thermometer

1 per class

3

Digital Thermometer Normal

1 per class

4

Maximum-Minimum Thermometer

1 per class

5

Observation sheet 2 – Worksheet 2

40

Things to do Check that all the thermometers are working correctly. Print as many copies as you need of observation sheet 2.

Safety Precautions Not Applicable

SESSION Understanding the parts of a thermometer Link to known information/previous activity We saw that the temperature of an object is a measure of how cold or cold it feels. Here we will see how to measure the temperature. Just like how we use ruler to measure length, we use a thermometer to measure temperature.

Procedure (Explanation by Instructor followed by observation sheet filling) Distribute observation sheet 2 to all the learners. Ask them to pay attention to the labeled diagram of the thermometer.

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Explain the parts of a thermometer, and it’s working, as described below.

An instrument that measures temperature is called a thermometer. A thermometer has a scale marked on Chart 1: Parts of a thermometer it, which is used to read the temperature. Reading this scale is similar to reading the length of a line using a ruler. The temperature is the reading corresponding to the position of the liquid level in the tube.

There are two common types of thermometers: Laboratory thermometers and Clinical thermometers (show the two thermometers here) The laboratory and clinical thermometers are mercury thermometers. Alcohol is also used as the thermometer liquid in some cases.

The liquid (mercury or alcohol) is sealed into a fine capillary tube having a bulb at one end. The capillary tube is much thinner than the bulb. The rest of the volume of the tube is vacuum. When temperature increases, thermal expansion (explained in ABL 4) causes both the volumes of the glass bulb and the liquid to increase. Mercury expands more than glass; hence it is expands from the bulb and moves into the capillary tube. As the temperature increases, mercury expands further, rising higher in the capillary tube, giving a higher reading of temperature.

The distance between the ice-point (freezing point of water) and steam point (water boiling point) is divided into 100 equal parts. This scale was originally known centigrade scale. The present name (Celsius scale) was adopted to honour the Swedish astronomer Anders Celsius, who suggested this scale.

Ask the learners to fill the thermometer readings in observation sheet 2.

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(Answers for Instructor’s reference: 18, 22, 32, 4, 8; 88, -24 or -26, 90, -12 or -14, -30)

Figure 3 -Anders Celsius

UNDERSTANDING THE ACTIVITY Leading questions 1. If you make the capillary tube thinner and longer, what will happen?

2. Why don’t thermometers have water instead of mercury?

Discussion and Explanation Discussion Item 1: The following points are about how a thermometer works  If the capillary tube is made thinner and longer, the amount of expansion of the liquid remains the same, so the liquid will rise higher up for the same increase in temperature.  If water is used in thermometers, we would not be able to measure temperatures anything above 100 °C (212 °F) or below 0°C (32 °F). These two temperatures represent the boiling and freezing points of water, respectively.

Water remains as a liquid only between 00 C and 1000 C If you use the thermometer to measure the temperature of something hotter than boiling water (100°C), the water will turn from liquid to gas.

KEY MESSAGES  

Thermometers work on the principle that liquids expand when heated.

The quantum of expansion of the liquid is a measure of change in temperature.

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LEARNING CHECK If you insert a thermometer in hot water, and then remove it, what will happen to the reading in the thermometer? Why? (Answers for Instructor’s reference: The reading will start decreasing. The temperature of atmosphere is lesser than hot water, as the liquid cools it contracts, hence the level of the liquid in the capillary tube starts reducing) Time: 45 min

ABL 2.3 LEARNING OBJECTIVE – a) How to use a thermometer? b) Kinds of thermometers in use.

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker (250 ml, Borosil)

1 per class

2

Spirit lamp

1 per class

3

Laboratory Thermometer

3 per class

4

Clinical Thermometer

1 per class

5

Vertical stand

2 per class

6

Thread

7

Tripod stand

1 per class

8

Wire gauge

1 per class

9

Match box

1 per class

10

Dustbin with sand/water

1 per class

11

Water

12

Observation sheet 3 –

1 roll per class

500 ml per class 40

Worksheet 3

Things to do Print as many copies of observation sheet 3 is as many as you need.

Safety Precautions Not Applicable

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SESSION SESSION 2.3a Link to known information/previous activity We learnt how thermometers are designed. In this session, we will measure the temperature using a thermometer.

Procedure (Group Activity) Instructor Activity Distribute Observation sheet 3 to all learners and facilitate the following group activity.

Divide the entire class into four groups and assign them group names (scientists names or group 1, group 2, group 3 and group 4) Each group would perform a different activity for measuring the temperature. Group 1 will measure the temperature of boiling water, group 2 will measure the atmospheric temperature, group 3 will measure the soil temperature and group 4 will measure the body temperature of fellow teammates.

Each group’s activity would take ten minutes. After the activity, the groups would return to the class and start discussing the observations.

Group 1 Activity           

This group will use a Laboratory Thermometer Arrange the heating setup on a table as shown in Figure 4 Fill the beaker with 100mL of water.

Suspend the thermometer from the vertical stand, such that the bulb is inside the water.

Ensure that the bulb does not touch the base of the beaker.

Ask the learners to note the initial reading on the thermometer.

Turn on the burner and start heating the water.

Ask the learners to note the temperature every1 minute.

Continue the experiment for 10 minutes Turn off the spirit lamp after 10 minutes.

Students should continue to take observations every 1 minute for another 10 minutes.

Figure 4: Heating setup Agastya International Foundation. For Internal Circulation only.

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Group 2 Activity    

Ask the learners to measure the temperature inside the room.

Go outdoors to a location where there is no shade and there is direct exposure to the sun.

Either suspend the thermometer from a vertical stand or tie it with a thread to some support that you locate outdoors.

Ask the learners to note the reading every 1 minute for 20minutes

Group 3 Activity     

Go outdoors and select any location With a help of small iron rod or stick/stone, dig a small hole about 3 inches deep.

Fix the thermometer in the hole, such that the bulb of the thermometer is inside the soil.

Ensure the thermometer is stable and standing freely.

Ask the learners to note the temperature every 1 minute for 20 minutes.

Group 4 - Learner Activity   

Select a learner in the group. Place the clinical thermometer in the armpit of the learner for 2 minutes. Remove the thermometer and ask the learners to note the temperature observation.

Dip the thermometer in lukewarm water. Shake it well.

Ask the group to repeat the process with other members of the group. Ensure that the activity is completed within 20 minutes.

Ask all the groups to return to the classroom.

Teach them how to take the average reading. (Average = sum of observations / total number of readings) Ask them to take the average of their observations.

Facilitate the following discussion, one group at a time. Ensure that all the groups are present during the entire discussion.

UNDERSTANDING THE ACTIVITY Leading questions (common to all groups) 1. Whose temperature were you measuring?

2. What did you observe?

3. Is there a source of heat causing a change in the temperature?

Discussion and Explanation Group 1: Discussion Item 1: The following points are about how the temperature changes as the water was heated and cooled.

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 

The temperature of water was being measured.

It increased from ___ °C (refer to reading from learner’s observation sheet) when the water was heated.  The flame is the source of heat. The heat from the flame is being transferred to the water.

When the temperature reached 100°C, it remained at 100°C. When the burner was turned off and the water started cooling to room temperature, the temperature started decreasing.

The water was hottest at 100°C, when the temperature was the highest.

The water was coolest at room temperature, when the temperature reading is also the minimum.

Group 2 Discussion Item 1: The following points are about how the temperature of the atmosphere does not change much  The temperature of the atmosphere or surrounding air was being measured.  The initial reading was ___ °C (refer to reading from learner’s observation sheet) It would not have changed much; it may have changed initially while changing from room temperature to the atmospheric temperature.

The atmospheric temperature changes slowly over the day. It generally does not change much within 20 minutes.

Every day in newspapers and in news channels, there would be a reference to the weather, where the temperature of major cities will be shown. You have also measured the temperature of our local area but the difference is that we have only measured the temperature for 20 minutes, but when the news indicates the weather of a city, the temperature is taken over a whole day.  The source of heat is the sun, as the earth rotates, the intensity of solar radiation at a place changes and hence the temperature changes during a day.

Group 3 Discussion Item 1: The following points are about how the temperature of the soil does not change much  The temperature of the soil was being measured.  It would not have changed much.  Similar to the atmospheric temperature, the soil temperature does not change much over 20 minutes.

1. The source of heat in the soil is radiation from sun, conduction from surrounding atmosphere and pressure built up within the soil.

Group 4 Discussion Item 1: The following points are about the temperature of humans  The temperature of the learners was being measured individually  The temperature is approximately 37°C or 98.6°F.  It can vary by about a fraction of a degree from one learner to another.  Energy generated by metabolic activities like respiration give rise to heat in our body.

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KEY MESSAGES  

We use thermometers to measure temperature.

Temperature tends to remain constant unless there is heat transfer to or removed from an object.

LEARNING CHECK If you have a glass full of ice, and measure its temperature for a few hours, what will you observe?

(Answer for Instructor’s reference: The initial temperature would be 0°C. till all the ice melts and becomes water. The temperature would increase until it reaches the room temperature and then remain constant.

SESSION 2.3b Procedure (Explanation by Instructor) Ask the learners to pay attention to the Temperature Scales diagram on the last page of Observation Sheet 2, as you explain about the different temperature scales.

Scales of Temperature The ruler that we use generally has two scales – centimetres and inches. Similarly, there are three different scales to measure temperature.

1. Celsius Scale: On this scale, the ice point (melting point of ice) is 00C and the steam point (boiling point of water) is 1000C. The interval between these points is divided into 100 equal parts. Each of these divisions corresponds to one degree Celsius.

2. Fahrenheit Scale: On this scale, the ice point is 320F and the steam point is 2120F. The interval between these two reference points is divided into 180 equal parts. Each of these divisions corresponds to one degree Fahrenheit and is written as 0F. 3. Kelvin scale: The lowest possible temperature is – 2730 C. As substances get colder and its temperature reduces, gases condense into liquids and liquids freeze into solids. If the temperature continues to reduce, the molecules eventually they have their lowest possible energy. This happens at the coldest possible temperature, at – 2730 C, called absolute zero.

Lord Kelvin devised this scale which begins at absolute zero but increases just like the Celsius scale at the same rate. This means 00C becomes 273 Kelvin and 1000C becomes 373 K. Interval of 10 C is same as 10 K Ask the learners to refer to the last page Observation Sheet 2 for the conversions between the scales.

Write out the conversions on the Black Board.

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Conversion between scales: Celsius to Fahrenheit Fahrenheit to Celsius Celsius to Kelvin Kelvin to Celsius

0

F = 9/5 0C + 32 0 C = (0F – 32) 5/9 K = 0C + 273 0 C = K – 273

Ask the learners to work out the two conversion questions on Page 4 of the observation sheet 2.

(Answers : 323K, 1220F)

UNDERSTANDING THE ACTIVITY Leading questions 1. In what scale do we generally represent the atmospheric temperature, which indicates how hot, or cold the weather is?

2. Can the temperature of human body be measured in Kelvin? Why doesn’t the clinical thermometer indicate the readings in Kelvin?

Discussion and Explanation Discussion Item 1: The following points are about the use of different temperature scales  Atmospheric temperature is generally represented in 0°C or 0°F. In some countries, one of the two scales is more commonly used.  Human body temperature can be represented in Kelvin. It is not wrong. But it would be inconvenient, since the temperature would always be above 300K.

KEY MESSAGES  

Depending on the purpose of the thermometer, it can have a different temperature range.

There are three temperature scales – degree Celsius, degree Fahrenheit and Kelvin.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

TRY IT YOURSELF If you have a thermometer at home, measure your temperature after taking a cold-water bath and when you return home after playing outside. Compare the temperatures.

If your laboratory has a laboratory thermometer, check the temperature every day at the same time for five days. Is it constant?

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INTERESTING INFORMATION Not Applicable

WEB RESOURCES http://thekidshouldseethis.com/post/29142329810

VOCABULARY Not Applicable

REFERENCES http://www.physics4kids.com/files/thermo_scales.html

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ABL 3 – EFFECTS OF HEAT Activity Learning Objective 3.1 Effect of heat on a substance can result in Change in temperature

 

3.2

Measurement of quantity of heat supplied to a substance

3.3

To understand the relation between change in temperature and the nature of the substance (Specific heat)





Key message We use thermometers to measure temperature.

The change in temperature is directly proportional to the amount of heat supplied for that material.

Time (Min) 30

Heat is a form of energy and can be measured. When heat is supplied for time t by a source of power P, the energy supplied = P x t

15

If the mass of the water is M, and its temperature increases by ΔT, Heat Energy absorbed (Q) = M x c x ΔT, where c is the specific heat of water. The rise in temperature, ΔT is inversely proportional to specific heat.

15

TOTAL TIME

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INTRODUCTION Effects of heat on a body can result in a) Change in temperature b) Change in dimension c) Change in state a) Change in Temperature and Specific Heat  When heat energy is added to a substance, it results in an increase in the kinetic energy of its particles.  Since temperature is a measure of the average kinetic energy, the temperature increases.  The amount of temperature increase for a given body will depend on the amount of heat added, the mass of the body and the material it is made of.  The specific heat (of a material) is the amount of heat required to raise the temperature of one kilogram of the substance by one degree (0C or K). b) Change in Dimension  When heat is added to a solid, the particles gain energy and vibrate more vigorously about their fixed positions, forcing each other further apart. As a result expansion takes place.  Similarly, the particles in a liquid or gas gain energy and are forced further apart.  The degree of expansion depends on the substance.  For a given rise in temperature a liquid will expand more than a solid.  Gases expand enormously on heating than liquids. c) Change in State  When solids are heated continually, most solids changes state from solid to liquid at a temperature known at the melting point of the solid.  The melting point of various materials is different.  Not all solids melt into liquids upon heating.  When a liquid is heated continuously, it changes to a gas at a temperature called its boiling point.  Evaporation occurs on the surface of a liquid when a liquid changes to a gas at a temperature even below its normal boiling point.  The process of change in state of a liquid to a gas (due to boiling or evaporation) is called vaporization.  The change in state of a gas to a liquid when the gas is cooled is called condensation.  In general a solid substance when heated continuously, transforms into a liquid and then into a vapour.

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ABL 3.1

Time: 30 min

LEARNING OBJECTIVE –Effect of heat on a substance can result in Change in temperature ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker (250 ml, Borosil)

1 per class

2

Spirit lamp

1 per class

3

Laboratory Thermometer

3 per class

4

Clinical Thermometer

1 per class

5

Vertical stand

2 per class

6

Thread

7

Tripod stand

1 per class

8

Wire gauge

1 per class

9

Match box

1 per class

10

Dustbin with sand/water

1 per class

11

Water

1 roll per class

500 ml per class

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity We learnt how thermometers are designed. In this session, we will measure the temperature of a substance using a thermometer.

Procedure (Group Activity) Instructor Activity Distribute Observation sheet 3 to all learners and facilitate the following group activity.

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Divide the entire class into four groups and assign them group names (scientists names or group 1, group 2, group 3 and group 4) Each group would perform activity for measuring the temperature. The activity would take 10 mints and after the activity the groups would involve in discussing the observations.

Group Activity           

This group will use a Laboratory Thermometer Arrange the heating setup on a table as shown in Figure 5.

Fill the beaker with 100mL of water.

Suspend the thermometer from the vertical stand, such that the bulb is inside the water.

Ensure that the bulb does not touch the base of the beaker.

Ask the learners to note the initial reading on the thermometer.

Turn on the burner and start heating the water.

Ask the learners to note the temperature every 1 minute.

Continue the experiment for 10 minutes Turn off the spirit lamp after 10 minutes.

Students should continue to take observations every 1 minute for another 10 minutes.

Figure 5: Heating arrangement for beaker with wire gauge, spirit lamp and tripod stand

Note to Instructor: This activity is repeated from previous ABLs. Do not conduct it again if students have done it in a previous ABL as per their standard.

UNDERSTANDING THE ACTIVITY Leading questions (common to all groups) 1. Whose temperature were you measuring?

2. What did you observe?

3. Is there a source of heat causing a change in the temperature?

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Discussion and Explanation Group 1: Discussion Item 1: The following points are about how the temperature changes as the water was heated and cooled.  The temperature of water was being measured.  It increased from ___ °C (refer to reading from learner’s observation sheet) when the water was heated.  The flame is the source of heat. The heat from the flame is being transferred to the water.

When the temperature reached 100°C, it remained at 100°C. When the burner was turned off and the water started cooling to room temperature, the temperature started decreasing.

The water was hottest at 100°C, when the temperature was the highest.

The water was coolest at room temperature, when the temperature reading is also the minimum.

KEY MESSAGES  

We use thermometers to measure temperature.

The change in temperature is directly proportional to the amount of heat supplied for that material.

LEARNING CHECK If you have a glass full of ice, and measure its temperature for a few hours, what will you observe?

(Answer for Instructor’s reference: The initial temperature would be 0°C. till all the ice melts and becomes water. The temperature would increase until it reaches the room temperature and then remain constant.

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Time: 15 min

ABL 3.2 LEARNING OBJECTIVE – Measurement of quantity of heat supplied to a substance ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker (1000 ml, Borosil)

1

2

Immersion heater (125 W)

1

3

Thermometer

1

4

Vertical stand

1

5

Stop clock

1

6

Wooden stick to stir water

1

7

Tripod stand (optional)

1

8

Wire gauge (optional)

1

Note to Instructor: 1: Power supply is necessary to use the immersion heater.

2: The two numbers that are important in this experiment are the quantity of water (m) and the wattage of the heater (p).

3: Place the heater on a wooden plank.

Things to do Mount the thermometer from the vertical stand, such that the end of the thermometer is immersed in water.

Safety Precautions Keep the immersion heater away from the learners.

The list of materials suggests a wooden stick to stir the water, when the electric heater is connected. Do not use a metal object to stir. You can get an electric shock.

Be cautious not to touch the heater or the water with hand while stirring with wooden stick Do not use a metal container instead of the beaker. It can cause an electric shock.

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SESSION Link to known information/previous activity We learnt that heat is a form of energy and also learnt how to measure the temperature of a substance.

We will now measure the heat energy transferred.

Procedure Pour exactly 500ml (500 gm) of water into the beaker.

Measure the initial temperature of water.

Show the immersion heater to the learners. Ask them to note down the wattage of the heater (p).

Immerse the electric heater in the water. You can put the cord over the retort stand, such that the heater is suspended from the stand as show in figure 3.1.2.

Connect the electric heater to the power supply and switch it on.

Figure 6: Experimental Arrangement to measure heat

Start the timer immediately.

Stir the water with the wooden stick occasionally.

Turn off the immersion heater after 4 minutes. Stir the water once.

Measure the temperature of the water.

On the blackboard, write the following and fill up the values.

Initial temperature: Final temperature: Rise in temperature (Final – Initial): Time heated: Power of heater:

UNDERSTANDING THE ACTIVITY Leading questions 1. What does the thermometer measure?

2. By measuring the temperature, can you measure the heat?

3. If we had used 1000ml of water instead of 500ml, what do you think the final temperature value would have been?

4. If we had heated for 8 minutes instead of 4 minutes, what do you think the rise in temperature value would have been?

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6. Have you heard the term energy? At this point you can write the words ‘Energy’ and ‘Power’ on the blackboard to draw their attention to the term.

Discussion and Explanation Discussion Item 1: The following points introduce the concept of energy in a simple way and bring out the idea that heat is also a form of energy.  The thermometer measures the rise in temperature.  By measuring the temperature you can measure the heat directly.  The rise in temperature would have been half of that observed for 500 ml.  If we had heated for 8 minutes instead of 4 minutes, the rise in temperature would be doubled.  Since the power is doubled the rise in temperature is also doubled.  Energy supplied equals to power multiplied by time. (Q = p x t)

KEY MESSAGES 

Heat is a form of energy and can be measured. When heat is supplied for time t by a source of power P, the energy supplied = P x t

LEARNING CHECK If we use a 200W water heater for 7 minutes to heat 2kg of water, at an initial temperature of 25°C, what would the final temperature be?

(Answer for Instructor’s reference: Energy supplied = 200x7x60 = 84000J. 84000 = 2000x4.2xΔT ΔT = 10.

Final temperature would be 25°C + 10°C = 35°C)

Time: 15 min

ABL 3.3 LEARNING OBJECTIVE: To understand the relation between change in temperature and the nature of the substance (Specific heat) ADVANCE PREPARATION Material List

S.NO

Material

Required Quantity

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1

Beaker (250 ml, Borosil)

1

2

Test tube

3

3

Coconut oil

4

Thermometer

3

5

Vertical stand

1

6

Salt

7

Water

8

Tripod stand

1

9

Wire gauge

1

10

Spirit lamp

1

100 ml

2 table spoons 500ml

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we learnt the relation between the heat energy supplied and the increase in temperature. Now we will see how the increase in temperature depends on the substance being heated.

Procedure Pour 15ml of water in the first test tube Pour 15ml of coconut oil in the second test tube Pour about 10ml of water in the third test tube. Add two table spoons of salt and mix. Add additional water to make the level reach 15ml.

Fill the beaker with 100ml of water and keep the three test tubes in the beaker.

With the help of the vertical stand, suspend the three thermometers in the three test tubes.

(Ensure that the tip of the thermometer does not touch the base of the test tube) Place the wire gauge on the tripod stand and keep the spirit lamp below it. Place the beaker on the wire gauge. Turn on the spirit lamp and start heating the water.

Ask the learners to observe the temperature of the thermometers.

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Stop heating after 15 minutes.

Note the temperature and write it on the blackboard.

UNDERSTANDING THE ACTIVITY Leading questions 1. What did you observe?

2. Were the four final temperatures the same?

Discussion and Explanation Discussion Item 1: The following points are to elaborate that the amount of increase in temperature of a substance depends on its specific heat  All four temperatures increased with time. This is because we were continuously supplying heat to all the liquids by heating through the spirit lamp.  The final temperatures are not the same. This is because the specific heats of the three liquids are different. Specific heat of a substance is the amount of heat required per unit mass to raise the temperature by one degree Celsius.

Q = M x c x ΔT, where M is the mass of the substance, c is the specific heat, ΔT is the increase in temperature.

If a substance has low specific heat, it requires lesser heat energy to raise its temperature by 1 degree.

Oil has lower specific heat than water. If you supply the same amount of heat to equal quantities of water and oil, the temperature of oil rises more than water.

Salty water has lower specific heat than water, but higher than oil. So the temperature of salty water rises more than normal water but less than oil.

KEY MESSAGES 

If the mass of the water is M, and its temperature increases by ΔT, Heat Energy absorbed (Q) = M x c x ΔT, where c is the specific heat of water. The rise in temperature ΔT is inversely proportional to specific heat.

LEARNING CHECK If you heat oil and water for the same time and both reach the same temperature after some time, how do the quantity of oil and water compare?

(Answer for Instructor’s reference: Quantity of oil is more than water since specific heat of oil is lesser than water)

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TRY IT YOURSELF On a hot day, touch different objects kept outdoors such as parts of a bicycle, leaves, wood, metal pieces, water and see which ones feel hotter than others. On a cold day, touch the same objects and see how they feel. You should observe that objects such as metals become hotter than wood on hot days and colder than wood on cool days since metal has lower specific heat.

INTERESTING INFORMATION The high specific heat capacity of water helps regulate extreme temperatures in the environment. For instance, fishes in ponds are happy because the high specific heat of the water means the temperature of the water will stay relatively the same from day to night.

This same concept can be expanded to a worldwide scale. The oceans and lakes help regulate the temperature ranges that billions of people experience in their towns and cities. Water surrounding or near cities take longer to heat up and longer to cool down than do land masses, so cities near the oceans will tend to have less change and less extreme temperatures than inland cities. This property of water is one reason why places on the coast and in the center of the land mass can differ so much in temperature patterns.

WEB RESOURCES http://www.youtube.com/watch?v=DQBQQaku6Js http://schools.wikia.com/wiki/Specific_Heat

VOCABULARY Energy: Energy is the ability of a physical system to perform work.

Power: Power is the amount of energy consumed per unit time.

Specific Heat: Specific heat is the amount of heat required to raise the temperature of a unit mass of a given substance by a degree.

REFERENCES http://ga.wateener.usgs.gov/edu/heat-capacity.html

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ABL 4 – EFFECT OF HEAT ON DIMENSION Activity 4.1

Learning Objective What is the effect of heat on the length and volume of a solid?

4.2

Understanding the dependence of expansion on nature of the material (coefficient of thermal expansion)

4.3

What is the effect of heat on volume of liquids?

4.4

4.5

Relation between the expansion of liquids and their thermal coefficients

Change in Dimension Expansion of Gas





Key message When a solid is heated, the kinetic energy of the molecules increases, causing the solid to expand.

Time (Min) 20

The increase in length, area or volume of different solids, when subjected to heat is proportional to their thermal coefficient of expansion.

10

Generally Liquids expand on heating and contract on cooling

10



Liquids expand on heating and contract on cooling, but the rate of expansion/contraction depends on the thermal coefficient of expansion, which is different for different liquids.

10



Gases expand on heating and contract on cooling, but the rate of expansion/contraction is higher than liquids and solids.

15



TOTAL TIME

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Time: 20 min

ABL 4.1 LEARNING OBJECTIVE – What is the effect of heat on the length and volume of a solid?

ADVANCE PREPARATION Material List S.NO

Material

1

Model 1: Thermal/Linear

Required Quantity 1 per class

Expansion model (Wire clamped on both ends with a copper ball hanging from it) 2

Model 2: Ball and ring model

1 per class

3

Spirit lamp

1 per class

4

Match box

1 per class

5

Dustbin with sand/water

1 per class

(Note to Instructor: Even if you have only one of the two models, you can proceed with this activity) Things to do Check that both models work by heating the copper wire of Model 1 and the ball of Model 2 and noticing the expansion.

Figure 7 -Linear Expansion Model

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Figure 8 – Ball and Ring Model Safety Precautions Not Applicable

SESSION (Depending on which model is available, perform the suitable experiment/both experiments) Link to known information/previous activity We saw the temperature of a liquid increases when it is heated. Next we will see the effect of heat on solids.

Procedure (Model-1 to be used for this session) Light the spirit lamp with a matchstick.

Call any learner and ask him to heat the copper wire with the spirit lamp.

Stop heating after you notice the wire sagging upon heating and lowering of the hung copper ball Allow it to cool for a few minutes till you see the wire contracting back to original length and copper moving up to the original level.

(Model-2 to be used for this session) Light the spirit lamp with a matchstick.

Call any learner and ask him to insert the ball into the ring. It should go in smoothly.

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Help the learner heat the ball using the spirit lamp.

Call another learner and ask him to insert the ball in the ring. The ball should now not go through the ring.

Dip the ball in water for about a minute.

Ask the learner to again attempt to insert the ball through the ring. The ball should now go through the ring.

UNDERSTANDING THE ACTIVITY Leading questions (Model 1) 1. Before we started heating, how did the setup of the wire and ball look like? Why was the wire held tight?

2. What happened to the wire and the ball when you heated and why?

3. What did you observe when you stopped heating?

4. Why did we dip the ball in water for a minute?

5. How do you explain the sagging of wire in model 1?

Leading questions (Model 2) 1. Before we started heating, how did the setup of the ring and ball look like 2. What happened to the ring and the ball when you heated and why?

3. What did you observe when you stopped heating?

4. What happened to the ball and the ring when the ball was heated?

5. Why did we dip the ball in water for a minute?

6. How do you explain the sagging of wire in model 1 and the ball not going through the ring in model 2?

Discussion and Explanation Model 1  Before we started heating, the wire was held tight because it is fixed tightly at the two ends.

The ball hangs from the straight/tight wire  Upon heating, the wire started sagging and the ball was lowered. This Because of the expansion of wire on heating  When we stopped heating, it started contracting and became tight again as it was initially. The ball returned to the original level.  The ball is dipped in water to bring it back to the room temperature.

Model 2   

Before we started heating, the ball comfortably slides through the ring.

Upon heating the ball expands and can no longer go through the ring.

The ball cools down when dipped in water. Upon cooling, it resumes its original smaller size and passes through the ring.

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The following points are about thermal expansion.

Note to Instructor: The following points are general information that you must tell the learners.   

Our observation is that solids expand on heating and contract on cooling.

The expansion of materials due to heating is called thermal expansion.

All substances are made up of molecules, which are in a state of vibration. These molecules have some average separation between them, which depends on the energy they have. When the substance is heated, the molecules get more energy, and start vibrating more rapidly with larger amplitude. This results in a larger separation between them, causing the solid to expand.

Upon cooling, the energy of the molecules reduces and the separation decreases, resulting in contraction of the solid.

KEY MESSAGES 

When a solid is heated, the kinetic energy of the molecules increases, causing the solid to expand.

LEARNING CHECK The electrical lines between two poles that we see on the roads outside are similar to these wires. What happens to them in summer and in winter?

(Answer) The electrical lines get heated in summer. They expand and become loose. In winter, they contract and are generally tight and straight.

Have you noticed the gaps in railway tracks? Why do you think they keep the gaps?

(Answer) Solids expand on heating. If a railway track expands, it will no longer be straight, and will start bending at some points and cause accidents. The gap is to make space for the thermal expansion of the railway track. Rivets are used to fix the steel frames. These are good examples of contraction. In general, these rivets nails are heated and plugged to the two frames/supports when they are hot, when it is cool, rivets will contract and pull the two frames/supports tightly.

Time: 10 min

ABL 4.2 LEARNING OBJECTIVE: Understanding the dependence of expansion on nature of the material (coefficient of thermal expansion) ADVANCE PREPARATION Material List S.NO

Material

1

Bimetallic strip

Required Quantity 1 per group

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2

Spirit lamp

1 per group

3

Match box

1

4

Dustbin with sand/water

1

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we saw that metal expands on heating. Now we will understand if all metals expand to the same extent or to a different extent.

Procedure (Group Activity) Divide the class into groups depending on the number of bimetallic strips available.

Give each group a spirit lamp to heat it.

Ask the learners – what do they think will happen when the strip is heated?

Ask the groups to heat their bimetallic strip with the lamp After heating for about a minute, ask them to stop heating Let it cool for about 2-3 minutes

UNDERSTANDING THE ACTIVITY Leading questions 1. Before starting the experiment, what did you expect to happen when you heat the metal strip?

2. What do you think this strip is made of?

3. What happened when you heated it and why did the strip bend and not expand uniformly in a neat manner?

Discussion and Explanation Discussion Item 1: The following points are about how the amount of expansion of materials depends on their thermal coefficient of expansion  Before starting the experiment, we expected the metal strip to expand on heating.  The strip is made of two materials of same length welded together. One side is copper and one side is iron.  Copper has a higher coefficient of thermal expansion than iron, when the strip was heated, both the metals were heated to the same amount, but copper expands more due to its higher Agastya International Foundation. For Internal Circulation only.

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coefficient of thermal expansion. However, since the two metals are welded together, when the copper strip increases in length as compared to the iron strip, it results in the bending.

(Coefficient of thermal expansion of a material is the increase in the size of the material of unit length when heated through 10C)

KEY MESSAGES 

The increase in length, area or volume of different solids, when subjected to heat is proportional to their thermal coefficient of expansion.

LEARNING CHECK Assume you have a glass jar with a steel lid and you cannot open the lid. From what we learnt in class today, do you have any idea on how we could open the lid?

(Answer) You can dip the lid of the jar in hot water. Glass has a lower coefficient of thermal expansion than steel. Hence, the steel lid will expand more than the glass and you could be able to open the jar.

TRY IT YOURSELF Let us try the glass jar experiment mentioned above. If you have a glass jar with steel lid at home, with the help of an adult seal the jar tight and then heat the lid. Use a cloth or towel to open the jar now. You should find it relatively easy to open the jar after heating.

INTERESTING INFORMATION All electric iron boxes have a thermostat. A thermostat regulates the temperature by automatically stopping or starting the heat. The thermostat in an electric iron is a bimetallic strip with a brass strip on one side and an iron strip on the other side as shown in the figure.

Figure 9: Iron box

WEB RESOURCES http://apphysicsc.com/thermal-expansion-solids-liquids-gases/ - Bimetallic strip in iron Agastya International Foundation. For Internal Circulation only.

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VOCABULARY AND DEFINITIONS Kinetic Energy: Kinetic energy of an object is the energy it possesses due to its motion.

Thermal Expansion: Thermal expansion is the tendency of matter to change its size in response to a change in temperature.

Coefficient of thermal expansion: It can be co efficient of linear expansion or volume expansion.

The coefficient of the linear expansion of the material of the solid is defined as the increase in length per unit length per one degree centigrade rise in temperature (Alfa) its value is different for different materials.

The coefficient of volume expansion of liquid or a gas is defined as the increase in volume per unit volume per one degree centigrade rise in temperature (Gamma) Its value is different for different materials.

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ABL 4.3

Time: 10 min

LEARNING OBJECTIVE – What is the effect of heat on volume of liquids?

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Test tube

1 per class

2

Test tube holder

1 per class

3

Test tube rubber cap with one hole

1 per class

4

Empty refill

1 per class

5

Water

500ml per class

6

Potassium permanganate crystals

3 to 5 per class

7

Spirit lamp

1 per class

8

Match box

1 per class

9

Dustbin with sand/water

1 per class

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity We saw the effect of heating solids. We saw that solids expand on heating. Now we will see the effect of heat on liquids.

Figure 10: Experimental arrangement for effect of heat on volume of Liquids Procedure Fill the test tube half way with water. Add a few potassium permanganate crystals to the water to make the water pink. This is just for our observation.

Close the end of the test tube with the rubber cork.

Ask the learners to observe the water level. Measure the level using a scale and make a note of it.

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Light the spirit lamp and heat the test tube for 2 to 3 minutes and stop.

Ask the learners to observe the water level. Measure and make note of it.

Cool the test tube by immersing the base into water.

Ask the learners to observe the water level. Measure and make note of it.

UNDERSTANDING THE ACTIVITY Leading questions 1. What happened to the water level on heating?

2. Why did we immerse the test tube in water?

3. What happened after immersing the test tube in water?

Discussion and Explanation Discussion Item 1: The following points are about water expanding and contracting on heating and cooling respectively.  On heating, the water level rises.  The test tube was immersed in water to cool back to the room temperature.  On immersing, the liquid level lowered and came back to original position.

Discussion Item 2: The following points are about thermal expansion (Note to Instructor: If you have covered ABL4, this can be skipped or explained in brief)  Our observation is that water expands on heating and contracts on cooling.  The expansion of water due to heating is called thermal expansion. Similar to liquids, solids also exhibit thermal expansion.  All substances are made up of molecules. These molecules have some average separation between them, which depends on the energy they have. When the substance is heated, the molecules get more energy, and start moving more rapidly. This results in a larger separation between them, causing the liquid to expand. Upon cooling, the energy of the molecules reduces and the separation decreases, resulting in contraction of the liquid. The thermal expansion of liquids is generally much more than solids – the increase in volume of a liquid is generally more than the increase in volume of a solid. This is because the molecules of liquids are held more loosely together than the solids, hence they move further apart from each other upon heating and occupies larger volume. The increasing volume is directly proportional to the increasing temperature.

KEY MESSAGES 

Liquids expand on heating and contract on cooling

LEARNING CHECK How does a thermometer work?

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(Note to Instructor: The learners should have come across this in ABL 2, but we reinforce the point here) (Answer) Thermometers have a bulb, which is filled with liquid mercury, and a thin capillary tube. When the bulb is touching a hot surface, the liquid mercury expands in volume and rises up the capillary tube  Generally liquids expand on heating and contract on cooling but water has an unusual expansion pattern.  When water is cooled from 4°C to 0°C, it expands instead of contracting. This property is called the anomalous expansion of water. Similarly on heating water from 0°C to 4°C, it contracts instead of expanding. Above 4°C, it expands similar to other liquids.  Have you wondered why a lake does not freeze completely but instead has a layer of ice on top and water below?  As the top layers of a lake get cooled, they contract, become denser and hence sink to the bottom. The less dense and warmer layers of water move up towards the surface. They in turn get cooled and move down again. This process repeats till the water reaches 4°C.  When cooled below 4°C, the water expands. Thus the cooler layer of water on the surface is now less dense, lighter and remains on top. It freezes and forms an ice layer on top, keeping the layers under it between 0°C and 4 °C.

Time: 10 min

ABL 4.4 LEARNING OBJECTIVE - Relation between the expansion of liquids and their thermal coefficients ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Boiling test tube

3 per class

2

Beaker

3 per class

3

Test tube rubber cap with one hole

3 per class

4

Empty refill

3 per class

5

Water

200ml per class

6

Coconut Oil

200 ml per class

7

Milk

200 ml per class

8

Spirit lamp

3 per class

9

Match box

1 per class

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10

Dustbin with sand/water

1 per class

11

Tripod stand

1 per class

12

Wire gauge

1 per class

Things to do Fill the first test tube with water, the second with milk and the third with coconut oil. Make sure you will the same level in all the test tubes.

Make a 3x3 table on the black board as shown below:

Initial

Level of Liquid After heating

After cooling

Water Milk Coconut Oil Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we saw that water expands on heating and contracts on cooling. Now we will compare the effect of heat on different liquids.

Procedure Divide the learners into three groups.

Hand over the three test tubes that you prepared to the three groups.

Light the three spirit lamps and give one to each group. Hand over the empty refill and test tube rubber cap.

The following instructions are to be followed by each group:  Light the spirit lamp and heat the test tube for 2 to 3 minutes and stop. 

Observe the water level. Measure and make note of it.



Cool the test tube by immersing the base into water.



Observe the water level. Measure and make note of it.

Ask the three groups for the values they noted and fill up the table on the blackboard.

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UNDERSTANDING THE ACTIVITY Leading questions 1. What did you observe from the table?

2. Do all the liquids expand and contract at the same rate?

Discussion and Explanation Discussion Item 1: The following points are about the thermal coefficient of thermal expansion of liquids.  Similar to the previous activity, for each liquid, we observe:  Before we started heating, the level is constant.  Upon heating, it expands. Hence the level rises.  Upon cooling, it contracts. Hence the level falls.

Comparing the liquids, we observe that while heating, the coconut oil level rose higher than the milk level, which rose higher than the water level. While cooling, we observe that in the same time, the decrease in level of coconut oil is higher than milk, which is higher than water.  Since the level of increase in water in a fixed time is a measure of the rate of expansion, we infer then the coconut oil has a higher coefficient of thermal expansion than milk, which is higher than the coefficient of expansion of water.

Different liquids have different coefficients of thermal expansion. Mercury is used in thermometers. It has a much higher coefficient of thermal expansion

KEY MESSAGES 

Liquids expand on heating and contract on cooling, but the rate of expansion/contraction depends on the thermal coefficient of expansion, which is different for different liquids.

LEARNING CHECK Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

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ABL 4.5

Time: 15 min

LEARNING OBJECTIVE: Change in Dimension - Expansion of Gas ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Plastic bowls

3

2

Plastic water bottle

1

3

Balloons

1

4

Hot water

500ml

5

Cold water

500ml

6

Normal water

500ml

7

Thread

1 roll

8

Scissors

1

(Note to Instructor: If cold water is not available, the experiment can still be done with hot and normal water) Things to do Keep the hot water ready before the class starts Safety Precautions Not Applicable

SESSION Link to known information/previous activity We observed that solids and liquids expand on heating and contract on cooling. We will now see if gases exhibit a similar effect.

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Procedure

Figure 11: Effect of heat on volume of gases Fill the three plastic bowls with normal water, cold water and hot water respectively.

Put the balloon’s end around the mouth of the bottle as shown in figure 3.1.3.

Tie it with a thread if necessary. Make sure that air cannot escape from the balloon outside the bottle.

Keep the bottle in normal water for a minute.

Next, keep the bottle in cold water for about two minutes.

Next, keep the bottle in hot water for about two minutes.

UNDERSTANDING THE ACTIVITY Leading questions 1. What did you observe and what is there inside the balloon?

2. How is the water in the bowl affecting the balloon?

3. Do all the gases expand and contract at the same rate?

Discussion and Explanation Discussion Item 1: The following points are about the thermal expansion of gases  Air is present inside the balloon and the bottle.  When the bottle is placed in hot or cold water, due to the temperature difference, the air inside the bottle also becomes hot or cold respectively.

The molecules of a gas are held together very very loosely than the molecules of a liquid, and a gas expands more than a liquid. Gases in general have higher coefficient of thermal expansion than liquids.

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

Gases contract on cooling. This explains why we saw the balloon deflate when the bottle was placed in cold water.

It is interesting to know that all gases expand or contract at the same rate when heated or cooled.

KEY MESSAGES 

Gases expand on heating and contract on cooling, but the rate of expansion/contraction is higher than liquids and solids.

LEARNING CHECK Have you seen hot air balloons flying in the sky? How do they rise towards the sky?

Figure 12 – Hot air balloon As you can guess from the name, hot air balloons are filled with hot air. We learnt that air expands when it is heated. When air expands, the molecules move apart, and the same volume of air now has lesser molecules. This makes hot air less dense. Hot air being less dense than the surrounding air, it rises up taking the balloon with it.

TRY IT YOURSELF Try out the experiment we performed in class at your home. Take an empty glass bottle and place a balloon over its mouth. Place the bottle in hot water and watch the balloon expand. Observe what happens after some time if you stop heating the water.

You can also try the following experiment under the supervision of an adult. Blow up a balloon and tie off the end. Place it above a burning candle and wait for it to explode. The air inside expanded quickly and popped the balloon. Now, blow up another balloon and fill it up part way with water before you tie off the end. Place the balloon over the candle. It will not pop because the water inside the balloon absorbs the heat. Because the water absorbs the heat, the air does not expand, thus keeping the balloon intact. http://www.ehow.com/info_8320986_thermal-expansion-science-experiments-kids.html

INTERESTING INFORMATION Under equal pressure, all gases expand at the same rate. This property is different from solids and liquids where the rate of expansion depends on their thermal coefficient or nature. It indirectly suggest the absence of any kind of binding between the atoms or molecules Agastya International Foundation. For Internal Circulation only.

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WEB RESOURCES http://www.inkpotamus.com/content/anomalous-expansion-of-water A poem on the anomalous expansion of water! http://www.ehow.com/info_8320986_thermal-expansion-science-experiments-kids.html

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ABL 5 – CHANGE OF STATE Activity Learning Objective 5.1 Change of state - Melting



  5.2

Change of state - Boiling







Key message When solids are heated continually, most solids change state from solid to liquid at a temperature known at the melting point of the solid.

The melting point of various materials is different.

Not all solids melt into liquids upon heating.

When a liquid is heated continuously, it changes to a gas at a temperature called its boiling point. The boiling point is different for different liquids.

The process of change in state of a liquid to a gas (due to boiling or evaporation) is called vaporization.

The change in state of a gas to a liquid when the gas is cooled is called condensation.

TOTAL TIME

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Time (Min) 15

20

35

Time: 15 min

ABL 5.1 LEARNING OBJECTIVE – Change of state - Melting

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Wax

Sufficient to break into 4 pieces, each at least the size of a dice

2

China dish/ ceramic container

4

4

Spirit lamp

4

5

Tripod stand

4

6

Wire gauge

4

7

Match box

1

8

Dust bin with sand/water

1

(Note to Instructor: It is not necessary to divide the class into 4 groups since all the groups are performing the same experiment. Depending on the availability of materials and the number of learners you can either perform the experiment for the whole class or let them do it in groups) Things to do Break the wax into small pieces (about the size of a dice), such that each group gets a piece Get the heating setup ready. Place the wire gauge on top of the tripod stand and place the spirit lamp below it. If you are dividing the class into groups for this activity, get all the groups’ heating setup ready.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activities, we saw that solids, liquids and gases expand on heating. Now we will see what happens when you continue to heat a solid for a long time.

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Procedure Divide the class into 4 groups and distribute the materials.

Ask the groups to place the wax in the china dish/ ceramic container, and place the dish on the wire gauge.

Dip a thermometer in between wax pieces.

Turn on the spirit lamps for each group.

Ask the groups to observe the wax as it continues to be heated.

Turn off the spirit lamps once the all groups wax pieces melt.

Ask the groups to observe the wax for some more time till it solidifies.

(Note to Instructor: Ask the learners not to touch the wax anytime after it starts getting heated, to avoid burning their finger)

UNDERSTANDING THE ACTIVITY Leading questions 1.

2.

3.

4.

5.

6.

7.

8.

What is the ‘state’ of the wax initially?

What happened when the wax was heated?

What happened when you stopped heating and let the wax cool?

What would happen when you heat ice?

What would happen when you heat a piece of iron for long?

Why is the mercury in a thermometer in liquid state and not in solid state?

What happens when you heat paper?

What happens when you heat camphor?

Discussion and Explanation Discussion Item 1: The following points are about the wax changing state from solid to liquid at its melting point  The wax was initially in solid state.  Upon continuously heating the wax, its temperature keeps increasing.  At some point, the wax changes from solid to liquid state. This happens at the ‘melting point’ of wax, which is around 45-50°C.  While melting of the wax, its temperature does not change.  A solid has a rigid structure due to the strong forces of attraction between the molecules. When a solid is heated, the molecules gain sufficient energy to vibrate rapidly and this structure is weakened. This has the effect of expansion of solids. Further heating provides more energy until the molecules start to break free of the structure. Though the particles are still loosely connected, they are able to move around. At this point, the solid is melting to form a liquid and all the heat absorbed is used only in breaking this structure and not heating the substance.

Hence the temperature remains constant.

Discussion Item 2: The following points are about various substances having different melting points Agastya International Foundation. For Internal Circulation only.

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    

Wax has a melting point of about 45-50°C. Ice melts at 0°C. It melts without being heated, if the ambient temperature is above 0°C. Mercury has a melting point of -38.8°C. Hence at room temperature, it is in liquid form.

Iron on the other hand has a very high melting point – greater than 1000°C. Hence in our daily lives we never see liquid iron.

Not all solids melt into liquid upon heating. For example, paper undergoes a chemical reaction when heated and burns/chars rather than melting. Camphor changes from solid to gaseous state upon heating. This is called sublimation.

Discussion Item 3: The following points are about the freezing point of liquids  When the liquid wax began to cool, it solidified. The temperature at which a liquid turns to solid state is called the freezing point of the liquid.  Typically the melting point of a solid and the freezing point of the liquid are the same.

KEY MESSAGES   

When solids are heated continually, most solids change state from solid to liquid at a temperature known at the melting point of the solid.

The melting point of various materials is different.

Not all solids melt into liquids upon heating.

LEARNING CHECK What do you think is the melting point of butter?

(Butter remains in solid state when kept outside the fridge in normal and cold weather but melts when kept outside in hot weather. Its melting point is 32-35°C.)

Time: 20 min

ABL 5.2 LEARNING OBJECTIVE – Change of state - Boiling ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker 250 ml, Borosil

2

Water

3

Laboratory thermometer

1 per class

4

Spirit lamp

1 per class

5

Tripod stand

1 per class

1 per class 100ml per class

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6

Wire gauge

1 per class

7

Match box

1 per class

8

Thick cardboard piece (lid for

1 per class

the beaker, through which the thermometer will be inserted) 9

Dust bin with sand/water

1 per class

Things to do Prepare a lid for the beaker with the cardboard piece. Pierce the cardboard to make a very small hole in it, such that the thermometer can be inserted through the cardboard, but not big enough for the thermometer to fall through the hole. The hole should be tight enough to hold the thermometer.

Get the heating setup ready. Place the wire gauge on top of the tripod stand and place the spirit lamp below it.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we learnt that when solids are heated, they melt into liquids when the temperature reaches their melting point. Now we will see what happens when liquids are heated continually.

Procedure Fill the beaker with 100ml of water and place it on the wire gauge. Place the cardboard lid on the beaker and insert the thermometer through it. Make sure the thermometer tip touches the water and not the base of the beaker.

Turn on the spirit lamp and start heating the water.

Ask the learners to observe the temperature change and the beaker with water.

Heat till the water boils. Once the water starts boiling, let it boil for about 15-20 seconds and then turn off the spirit lamp.

UNDERSTANDING THE ACTIVITY Leading questions 1. What is the ‘state’ of the water?

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2. What happened when the water was heated?

3. What were the fumes that were produced from the beaker?

4. How did the temperature change throughout the process?

Discussion and Explanation Discussion Item 1: The following points are about the change in state from liquid to gas at the boiling point.  As water is heated, its temperature rises. When the temperature reaches 100°C, water begins to get converted to water vapour. This temperature is called the boiling point of the liquid. This process is called vaporization.  When the water was continuously heated, the molecules get more and more energy. At the boiling point, the molecules of the liquid have sufficient energy to break the molecular bonds.

The Molecules on the surface escape as vapour.  On heating, the temperature of water continuously increases till it reaches a steady value about 1000 C. At this temperature all the heat energy supplied is used to transform water from liquid to gaseous state.

KEY MESSAGES 

When a liquid is heated continuously, it changes to a gas at a temperature called its boiling point. The boiling point is different for different liquids.  The process of change in state of a liquid to a gas (due to boiling or evaporation) is called vaporization.  The change in state of a gas to a liquid when the gas is cooled is called condensation.

Note to Instructor: It is advised to heat water in test tube rather than in a beaker to attain boiling point quickly

LEARNING CHECK When you take a water bottle from the fridge and keep it outside, why do you see drops of water on the bottle? Where is this water coming from?

(Answer for Instructor’s reference: Water vapors are present in the air. When water vapors in the air comes in contact with the cold surface of the bottle, it condenses into liquid on the surface of the bottle)

TRY IT YOURSELF On some days wet clothes might take longer to dry that on other days. Observe the difference in temperature and humidity (from weather forecast) on these days.

When water spills on the floor or when the floor is wet due to mopping, observe that some patches take longer to dry that the other. Why does that happen?

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INTERESTING INFORMATION 1

The earth has a limited amount of water. That water keeps going around and around and around and around and (well, you get the idea) in what we call the "Water Cycle". This cycle is made up of a few main parts:  Evaporation  Condensation  Precipitation  Collection

WEB RESOURCES http://www.youtube.com/watch?v=r8M7mah_QaY – A video for kids that covers boiling, freezing, melting, evaporation and condensation http://www.le.ac.uk/se/centres/sci/selfstudy/particle02.html http://www.kidzone.ws/water/ - the water cycle on earth

VOCABULARY 1) Melting: Melting is a physical process that results in the transition of a substance from solid to liquid state. The temperature at which this happens is called the melting point of the solid.

2) Boiling: Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point.

3) Freezing: Freezing, or solidification, is a phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point.

4) Vaporization: Vaporization of a substance is a phase transition from the liquid phase to gas phase. There are two types of vaporization – evaporation and boiling.

5) Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance.

6) Condensation: Condensation is the change of the physical state of matter from gas phase into liquid phase, and is the reverse of vaporization.

7) Latent heat: Latent heat is the energy absorbed or released by a system during a constanttemperature process. The latent heat of fusion or melting is the energy required for a 1 kilogram of a substance to change state from solid to liquid at the boiling point. The latent heat of vaporization is the energy required to transform 1 kilogram of substance from liquid to gas state.

ABL 6 – Conduction of Heat Activity Learning Objective 6.1 How is heat transferred from



Key message There are three methods of

1http://www.kidzone.ws/water/

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Time (Min) 10

hotter to colder regions?

heat transfer.

Conduction takes place when two objects are in contact with each other or within a single object. It can take place in solids, liquids or gases.  Convection is a method of heat transfer by the fluid movement of molecules and takes place in liquids and gases.  Radiation is the third method of heat transfer that can take place with or without a medium due to electromagnetic radiation.  Conduction is a process of heat transfer from one region to another by direct contact of the molecules, without movement.  Different materials conduct heat at different rates.  Not all materials are good conductors of heat.  Materials like Metals (Silver, copper etc.) are good conductors of heat.  Materials such as glass, plastic, wood are good insulators or bad conductors of heat. 

6.2

6.3

What is Conduction?

Do all materials conduct heat well?

TOTAL TIME

INTRODUCTION There are three methods of heat transfer a) Conduction b) Convection Agastya International Foundation. For Internal Circulation only.

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15

15

40

c) Radiation

Conduction  Conduction is the transfer of heat between substances that are in direct contact with each other.  Conduction occurs when a substance is heated.  The molecules, atoms and sub atomic particles will gain higher thermal energy and vibrate fast and transfer the heat to nearby molecules during collisions.  This process repeats and the solid slowly gets heated up.  Different materials conduct heat at different rates.

Convection     

Convection is a method of heat transfer by the fluid movement of molecules.

It takes place in liquids and gases.

Convection occurs when warmer region of a liquid or gas rise to cooler region in the liquid or gas.

Cooler liquid or gas then takes the place of the warmer region which has risen higher.

This results in a continuous circulation pattern known as the convection current and the liquid or gas gets heated up.

Radiation  Radiation is the transfer of energy to or from a body by means of the emission or absorption of electromagnetic radiation.  It does not rely upon any contact between the heat source and the heated object, as is the case with conduction and convection.  Darker colours absorb more thermal radiation that lighter colours.

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ABL 6.1

Time: 10 min

LEARNING OBJECTIVE – How is heat transferred from hotter to colder regions?

ADVANCE PREPARATION Material List

S.NO

Material

Required Quantity

1

Bundle of Ice cream sticks

At least three times the size of the class

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we introduced the idea of heat transfer. Next we will look at the exact process of heat transfer. This is a fun activity to introduce the learners to the three methods of heat transfer. We will name the three methods here, but will not explain the details in this activity.

Procedure (Group Activity) Ask the learners to sit in a semi-circle. Stand at one end of the semi-circle.

Show them the bundle of ice cream sticks and ask them to assume that: o The ice cream sticks are heat o You are the source of heat o Ask the learner at the end of the semi-circle furthest from you to raise his/her hand. We will look at the different ways of the transferring heat to this learner.

There are three possible ways for the transfer of heat.

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Process 1 Tell the learners to assume that they are molecules of a solid.

Ask them what movements the molecules of a solid can exhibit. The molecules of a solid cannot move around freely but they can vibrate in their position.

Give the bundle of sticks to the learner closest to you.

Ask each learner to keep one stick and pass on the bundle, until the bundle reaches the last learner.

Tell the learners that we will understand the process of conduction using this example.

Collect all sticks into a bundle.

Process 2 Tell the learners to assume that they are molecules of a liquid or gas.

Ask them what movements the molecules of a liquid or gas can exhibit. The molecules of a liquid or gas can move around freely.

Give the bundle of sticks to the learner sitting closest to you. Ask him/her to walk up to the last learner and give the bundle to the last learner.

Tell the learners that we will understand the process of convection using this example.

Collect all sticks into a bundle.

Process 3 We saw the transfer of heat in solids, liquids and gases.

Ask them what vacuum is. Vacuum is space where there is no matter – no molecules and atoms.

Ask them - what if we need to transfer heat to the last learner and there is only vacuum between you (the source of heat) and the learner?

Now throw the bundle of sticks to the last learner and ask him/her to catch it.

Tell the learners that we will understand the process of radiation using this example.

Tell them clearly that radiation can even happen when there is matter in between and not only in vacuum.

Collect all sticks into a bundle.

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Upon completion of the three processes, write on the blackboard: Process 1: Conduction Process 2: Convection Process 3: Radiation

UNDERSTANDING THE ACTIVITY Leading questions 1. What was common between processes 1 and 2?

2. How was process 3 different from 1 and 2?

3. In process 2, a learner walked up to the last learner and transferred the heat. Why could this not happen in process 1 and process 3?

4. Can process 1 take place in liquids and gasses too?

Discussion and Explanation Discussion Item 1: The following points bring out some key differences between the three processes 

In both process 1 and 2, heat was transferred through other molecules.



In process 3, no intermediate molecule participated in the process of heat transfer.



In process 1, since the learners were acting like the molecules of a solid, they could not move around freely. Hence they could only interact with their neighboring molecules are transfer heat.

In process 3, we were looking at an example of a system in vacuum where there are no molecules. Hence the other learners could not facilitate the heat transfer.



Process 1 can take place in liquids and gases too since collision of neighboring molecules due to vibration is possible in liquids and gases too.

KEY MESSAGES  

There are three methods of heat transfer.

Conduction takes place when two objects are in contact with each other or within a single object. It can take place in solids, liquids or gases.

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 

Convection is a method of heat transfer by the fluid movement of molecules and takes place in liquids and gases.

Radiation is the third method of heat transfer that can take place with or without a medium due to electromagnetic radiation.

LEARNING CHECK Why can convection not take place in solids?

Answer for Instructor’s reference: Convection is the transfer of heat by the movement of the particles of the substance. The particles (molecules, atoms, electrons) of a solid can only vibrate and cannot move freely, so convection does not take place in solids.

Time: 15 min

ABL 6.2 LEARNING OBJECTIVE – What is Conduction?

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Conduction model

1 per class

2

Small nails or bell pins

5 per class

3

Wax

Small piece

4

Candle or spirit lamp

1 per class

5

Match box

1 per class

6

Dustbin with sand/water

1 per class

7

Bucket with water

1 per class

8

Cloth to wipe the model

1 per class

when wet Things to do Not Applicable Safety Precautions Not Applicable Agastya International Foundation. For Internal Circulation only.

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SESSION Link to known information/previous activity In the previous activity, we saw how the medium of the material determines the types of heat transfer that can take place. Now, we will understand the process of heat transfer by conduction.

Procedure

Figure 13 – Conduction along a rod Call any two learners to the table and ask them to stick the nails to one of the rod in the model using wax.

There should be uniform gap (For example 2cm) between the nails. Do not stick a nail at the tip of the rod.

Refer to Figure 1.

Light the spirit lamp and hold the tip of the rod (that has the nails) over the flame.

Observe the falling of the nails.

Once the nails have fallen, ask the learners to write down their observation.

Now remove the nails and the wax stuck to the rod and dip the model in the water (to cool the rod and bring all rods to uniform temperature) Wipe the model with a cloth.

Ask another two learners to come to the table, and ask them to stick the nails at same intervals to all the rods using wax, as seen in Figure 2 Now heat the model at the center and observe the falling of nails

UNDERSTANDING THE ACTIVITY Leading questions 1. In the first experiment,  What is the source of heat?

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    2.    3.

Why did the nails fall off?

Which nail fell first and which fell last?

What can you infer about the flow of heat?

If we had heated the rod in the center instead of the tip, what would have happened?

In the second experiment, Are all the rods similar? If not, what is the difference between them?

In what order did the nails fall off?

What can you infer about the flow of heat in different materials from this observation?

Why didn’t your hand, which held apparatus feel hot?

Discussion and Explanation Discussion Item 1: The following points are about the conduction of heat in a solid.  The candle/spirit lamp is the source of heat.  When a part of the rod becomes hot enough to melt the wax stuck to it, the wax melts and hence the nail falls.  Conduction is the process of heat transfer within a substance or between two substances in contact with each other when there is a temperature difference. The molecules, atoms and subatomic particles in the hotter part will be vibrating faster since they have higher thermal energy.

When these molecules collide with the molecules of the cooler part, they transfer some energy.

In this way, the cooler molecules become slightly hotter, and can transfer the heat to their neighboring molecules. This is why the part of the rod closest to the heat source was the hottest, and slowly the heat propagated along the rod.  If we had heated the rod at the center, the nails near the center would have fallen off first.

Discussion Item 2: Different materials have different coefficients of thermal conductivity (k).  Each rod is made of a different material.  The nails in the different rods fell off at different times. This indicates that different materials conduct heat at different rates.  Thermal conductivity is a measure of the ability of a material to transfer heat. Given two surfaces on either side of the material with a temperature difference between them, the thermal conductivity is the heat energy transferred per unit time and per unit surface area, divided by the temperature difference. It is measured in watts per degree Kelvin.  Heat propagates faster in materials with higher thermal conductivity.  The thermal conductivity of a few materials is given below (in W/Km) o Copper: 401 o Aluminum: 205 o Brass: 109 o Glass: 1.05 o Wood: 0.05  Wood has a very low thermal conductivity. This is the reason very little heat got transferred to our hand from the hot apparatus.

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KEY MESSAGES  

Conduction is a process of heat transfer from one region to another by direct contact of the molecules, without movement.

Different materials conduct heat at different rates.

LEARNING CHECK If you heat a vessel and remove it from the stove, which part of the vessel would be the most comfortable to hold?

(Answer) The top of the vessel would be the warmest since the source of heat is present at the bottom and the vessel gets heated by conduction of heat.

Time: 15 min

ABL 6.3 LEARNING OBJECTIVE – Do all materials conduct heat well?

Note to Instructor: This activity is for Primary school level

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker 250 ml, Borosil

1 per class

2

Steel spoon

1 per class

3

Plastic spoon

1 per class

4

Ice cream stick

1 per class

5

Spirit lamp

1 per class

6

Match box

1 per class

7

Dustbin with sand/water

1 per class

8

Tripod stand

1 per class

9

Wire gauze

1 per class

Things to do Setup the heating apparatus with the spirit lamp, tripod stand, wire gauze and beaker. Fill the beaker half with water.

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Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we saw how metals conduct heat. We also saw that different metals have different thermal conductivity. Now we will look at the conductivity of a few other materials.

Procedure Place one steel spoon, plastic spoon and ice cream stick in the beaker filled with water.

Heat the water for about two minutes. Then turn off the heat.

Call three learners and ask them to touch the end (not in water) of the two spoons and the ice cream stick, one by one.

UNDERSTANDING THE ACTIVITY Leading questions 1. Did both the spoons feel hot?

2. How did the ice cream stick feel? When you eat ice-cream, does the ice cream stick feel cold?

3. In your kitchen, some vessels may have a wooden handle and some have a metal handle. Have you found one of them more comfortable to use than the other?

Discussion and Explanation Discussion Item 1: The following points are about wood and plastic being poor conductors of heat.  The steel spoon’s tip feels hot; the plastic spoon and ice cream stick do not feel hot at all.  Even when we have ice cream, the ice cream stick does not feel cold.  In the kitchen, the handle of cooking pans/heating vessels are made of wood or metal. The handles made of wood are easy to hold since they don’t get hot, whereas the handles made of metal get heated up and are difficult to hold.

We have seen that metals conduct heat due the transfer of energy due to vibrating atoms and free electrons. Insulators are materials than have a very low (almost zero) thermal conductivity.

This is due to the absence of free electrons can transfer the energy to neighboring molecules.

Wood, glass and plastic are examples of insulators.

KEY MESSAGES   

Not all materials are good conductors of heat.

Materials like Metals (Silver, copper etc.) are good conductors of heat.

Materials such as glass, plastic, wood are good insulators or bad conductors of heat.

LEARNING CHECK Which would you be more comfortable in holding? - A steel tumbler of hot tea or a glass tumbler of hot tea?

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(Answer for Instructor’s reference) Glass is a good insulator, whereas steel is a good conductor. So the glass tumbler will not get hot easily whereas the steel tumbler will.

TRY IT YOURSELF On a hot sunny day, touch different kinds of materials kept outdoors and try to guess which ones are good conductors and good insulators of heat.

Take a glass of ice-cold water and put a metal spoon and a pencil or ice cream stick in it. This is similar to the experiment with hot water that we performed. Is the same true for cold water? Think about this – what happens when you put cold water in a steel tumbler as compared to cold water in a glass tumbler?

INTERESTING INFORMATION Good conductors of heat are in general good conductors of electricity.

Silver is the only metal with higher thermal conductivity that copper but due to the high cost it is not used commonly!

Ice has a higher thermal conductivity than water, air and plastic.

WEB RESOURCES http://www.youtube.com/watch?v=w_IbPRNZ6ho – Nails on rod experiment as in ABL 7.3, and a few other simple conduction examples. http://www.youtube.com/watch?v=Atnjo7dD_bA – conduction, convection and radiation explained in a simple way.

VOCABULARY Thermal conductivity : Thermal conductivity is a measure of the ability of a material to transfer heat. Given two surfaces on either side of the material with a temperature difference between them, the thermal conductivity is the heat energy transferred per unit time and per unit surface area, divided by the temperature difference. It is measured in watts per degree Kelvin.

Thermal conductor: A thermal conductor is a substance that has relatively high thermal conductivity.

Thermal insulator: A thermal insulator is a substance that has relatively low thermal conductivity.

Conduction: The transfer of energy between objects that are in physical contact.

Convection: The transfer of energy between an object and its environment, due to fluid motion.

Radiation: The transfer of energy to or from a body by means of the emission or absorption of electromagnetic radiation.

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ABL 7 – Convection of Heat Activity 7.1

Learning Objective Convection – Heat transfer in Liquids

 

7.2

7.3

7.4

[Type text]

To see the process of convection in liquids.

Convection – Heat transfer in Gases

To see the process of convection in gases

Key message Liquids do not transfer heat by conduction but only transfer heat through convection.

Convection is the transfer of heat energy by the circulation of fluid as a result of the temperature difference within the fluid



Hot liquid rises and cold liquid moves down to take its place and thus causes the transfer of heat from base to the top.  This transfer takes place by the process of convection.  Gases transfer heat through convection, which is a process of heat transfer by the circulation or movement of heated parts of a gas. 

Hot air rises and cold air moves to takes its place. This movement of air is called the convection currents Total Time

Time (Min) 10

15

10

20

55

Time: 10 min

ABL 7.1 LEARNING OBJECTIVE: Convection – Heat transfer in Liquids ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Test tube

2

Water

3

Test tube holder

1

4

Spirit lamp

1

5

Match box

1

6

Dustbin with sand/water

1

1 100ml

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we briefly introduced the three types of heat transfer and looked at conduction in detail. Now we will look at convection in liquids, followed by convection in gases in the next activity Procedure Light the spirit lamp.

Fill the test tube 3/4th with water.

Hold it with the test tube holder in a slanting position such that you can heat the surface of water.

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Figure 14 – Experimental setup for convection Heat the water with the test tube in this position, till the water at the surface starts boiling. Ask the learners to come in turns and touch the base of the test tube.

UNDERSTANDING THE ACTIVITY Leading questions 1. How did the base of the test tube feel?

2. How do you think the surface of the water would have felt, had you touched it?

3. Why does the base of the test tube not feel hot, even when the water surface was boiling hot?

Discussion and Explanation Discussion Item 1: The following points are about the convection in liquids  Liquids too expand on heating and the same process happens when you heat liquids. Liquids too transfer heat by convection.  In this experiment, the source of heat was at the top of the liquid. Convection causes hot liquids to rise to the top. Hence, the liquid on the surface continued to be heated and remained on top. The liquid at the bottom of the test tube remained at the bottom and did not come in contact with the source of heat.  Since both water and glass are poor conductors of heat, only small amounts of heat were transferred through conduction. The base of the test tube does not feel hot when the water of the surface boiling.

KEY MESSAGES  

Liquids do not transfer heat by conduction but only transfer heat through convection.

Convection is the transfer of heat energy by the circulation of fluid as a result of the temperature difference within the fluid

LEARNING CHECK If we had heated the bottom of the test tube, would the water at the surface have felt hot?

(Answer for Instructor’s reference) Yes. The water at the bottom of the test tube would have risen to the top due to convection, and the process of this circulation of water would have continued. So the water at the surface would be hot.

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ABL 7.2

Time: 15 min

LEARNING OBJECTIVE – To see the process of convection in liquids.

ADVANCE PREPARATION Material List S.NO

Material

1

Borosil beaker 250 ml

2

Water

3

Potassium permanganate

Required Quantity 1 per class 200ml per class 2 per class

crystals 4

Chalk

1 per class

5

Dry grapes

5 per class

6

Dustbin with sand/water

1 per class

7

Tripod stand

1 per class

8

Wire gauze

1 per class

9

Match Box

1 per class

Note to Instructor: It is sufficient if either potassium permanganate crystals or chalk or dry grapes is available. All are not required.

Things to do If you are using a chalk for the experiment, make the chalk into chalk dust.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we saw the liquids transfer heat through convection. Now, we will see the process of convection in liquids.

Procedure Fill the beaker half with water.

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Set up the heating apparatus with the tripod stand, wire gauge and spirit lamp.

Put some chalk dust, the crystals of potassium permanganate or the dry grapes into the water.

Light the spirit lamp.

Ask the learners to observe the water in the beaker.

Let the heating continue for a few minutes after the water starts boiling, until the movement of the particles inside stops.

UNDERSTANDING THE ACTIVITY Leading questions 1. What is the position of dry grapes or chalk dust before heating?

2. What is happening as you heat?

3. How did the grapes/chalk dust move inside the beaker?

4. Who is carrying the dry grapes/chalk powder up and down?

5. After some time, why does the movement stop?

Discussion and Explanation Discussion Item 1: The following points explain the air circulation due to convection.      

In the previous experiment, we saw that heating a liquid in a test tube at the surface does not make the liquid at the bottom hot.

In this activity, we heated the liquid at the bottom, and we are able to see the process of convection. Heat is being transferred within the liquid.

When we start heating, the water at the bottom becomes hot. Liquids expand on heating and hence become less dense and lighter. This lighter liquid rises to the top.

The water at the surface is cold and heavier (denser). It moves downwards occupying the position of hot liquid that just moved up.

This process continues till all the water in the beaker is at the same energy (reaches same temperature).

The movement of the chalk dust/grapes/pink colour just shows us this movement of the liquid currents.

KEY MESSAGES  

Hot liquid rises and cold liquid moves down to take its place and thus causes the transfer of heat from base to the top.

This transfer takes place by the process of convection.

LEARNING CHECK Can convection take place in solids?

Answer for Instructor’s reference: No. Convection involves the movement of the particles of the substance. Hence it can only take places in gases and liquids, and not in solids.

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Time: 10 min

ABL 7.3 LEARNING OBJECTIVE – Convection – Heat transfer in Gases ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Candle

At least 1

2

Match box

1 per class

3

Dust bin with sand/water

1 per class

Things to do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we saw heat transfer through convection in liquids. We will now understand how gases transfer heat Procedure Depending on the number of candles and learners, divide the class into groups.

Fix all the candles on the floor and light them.

Ask the learners to take turns to keep one hand above the flame and another hand on the side of the flame. Ensure that the hand above the flame is kept at a safe distance from the flame.

UNDERSTANDING THE ACTIVITY Leading questions 1. Do both the hands feel equally warm?

2. Which hand feels warmer?

3. What happens to the volume of a gas when it is heated?

Discussion and Explanation Discussion Item 1: The following points are about the process of convection

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    

Just to recap – Gases expand on heating (So do solids and liquids). This thermal expansion is because hotter gas molecules have higher kinetic energy, causing them to move about more rapidly and occupy a higher volume.

Hotter gas occupies a higher volume and hence is less dense, or is lighter.

This causes hotter gas to rise. Cold gas moves down to occupy its place.

In the case of the candle, the flame heats the air that is close to it. This is by a process of radiation that we will see in the next activity. This is also the reason why the hand on the side of the flame feels hot.

The hot air around the candle flame starts rising. This is the reason the hand above the flame feels much warmer than the hand on the side.

KEY MESSAGES 

Gases transfer heat through convection, which is a process of heat transfer by the circulation or movement of heated parts of a gas.

LEARNING CHECK Why are exhaust fans placed at the top and not at the bottom, in rooms?

(Answer) We breathe in fresh air and breather out warmer air, which rises. In places such as kitchens, the warm air is due to the cooking. In both cases, we use exhaust fans to eliminate the warm air and hence they are placed at the top.

Time: 20 min

ABL 7.4 LEARNING OBJECTIVE - To see the process of convection in gases ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

Required for Procedure

1

Convection model

1 per class

2

Incense sticks

1 per class

3

Sheet of paper

1 per class

4

Scissors

1 per class

5

Thread

1 per class

6

Vertical stand to hang paper

1 per class

a

B

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7

Match box

1 per class

8

Dust bin with sand/water

1 per class

9

Candle

1 per class

Both

Note to Instructor: Depending on the availability of the above materials you can do either one or both of the activities.

Things to do If a convection model is not available, you can make one with a cardboard box such that it is as shown in the figure. Ensure that one side is transparent such that the convection of air inside the box can be viewed.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity In the previous activity, we experienced hot air above a candle flame due to convection. Now we will see convection currents.

Procedure a Light a candle such that it is under one chimney. Call this chimney A and the other chimney as chimney B Light an incense stick. The incense stick helps in seeing the movement of the air current since the fumes are visible.

Figure 15 – Convection model 1 Place the incense stick above chimney A. Keep the stick such that the fumes go into the chimney.

Ask the learners to observe the air currents through and inside the box.

Next, place the stick above the chimney B. Again, ask the learners to observe the air currents.

Procedure b Draw a spiral on the paper and cut it along the spiral lines.

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Tie one end of the paper with a thread and hang it with a thread to the vertical stand (as seen in figure).

Place a candle below. Do not light the candle.

Figure 16 – Convection model 2 Ask the learners to observe the paper.

Now, light the candle. Make sure that the flame does not touch the paper.

Ask the learners to observe the movement of the paper.

UNDERSTANDING THE ACTIVITY Leading questions (a) 1.

2.

3.

4.

What is the purpose of the candle?

What is the purpose of the incense stick?

What air going in or out through the first chimney?

What air going in or out through the second chimney?

(b) 1. What happened to the spiral paper after lighting the candle? Why? Discussion and Explanation Discussion Item 1: The following points explain the air circulation due to convection. (a)     

The candle is the source of heat. It heats up the air in this experiment.

Air is colourless and it is not possible to view its flow. But the fumes of the incense stick have a colour and are easy to view in motion.

In both cases, the air above the candle gets heated and moves up through chimney A. Cold air has to occupy its place. So cold air moves in through chimney B. In the first case, since the incense stick is placed above chimney A, it is easy to view the rise of the hot air.

In the second case, it is easy to view the movement of cold air into chimney B since the fumes of the incense stick will go into the box through chimney B.

(b)  

Hot air rises and cold air moves down to take its place.

Due to this movement of air around the spiral paper, the spiral starts twisting.

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KEY MESSAGES 

Hot air rises and cold air moves to takes its place. This movement of air is called the convection currents.

LEARNING CHECK A room heater is placed in a corner of the room. How does the whole room become hot?

(Answer) The heater heats the air around it (by radiation, which we will learn soon). This air rises and cold air moves in to take its place. Soon this air also becomes hot and rises. This process continues and the entire air in the room becomes hot. The circulation of air continues as long as the heater is on.

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ABL 8 – Radiation of Heat Activity 8.1

8.2

Learning Objective How does heat from the sun travel to the earth?

The response of black and white objects exposed to thermal radiations.

 



Key message The sun’s heat reaches us through thermal radiation.

This radiant energy is absorbed by the vanes, which tend to rotate.

Darker colours absorb more thermal radiation than lighter colours.

Total Time

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Time (Min) 15

25

40

ABL 8.1

Time: 15 min

LEARNING OBJECTIVE – How does heat from the sun travel to the earth?

ADVANCE PREPARATION Material List S.NO

Material

1

Radiometer model

Required Quantity 1 per class

Things to do This activity is to be performed outdoors in the presence of the sun.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity So far, we have seen two methods of heat transfer – conduction and convection. However, both these methods need a medium – solid, liquid or gas. However, a majority of the distance between the earth and the sun is vacuum. Yet, heat reaches us from the sun. We will see a third type of heat transfer mechanism.

Procedure Take the learners outdoors. Ask them to sit in a circle.

Place the radiometer in the sunlight, in the center of the circle.

Ask the learners to observe the radiometer.

Now bring back the learners to the classroom and place the radiometer on a table.

Figure 17 - Radiometer After some time, rub the bulb of the radiometer and ask the learners to observe.

UNDERSTANDING THE ACTIVITY Leading questions 1. What happened to the radiometer in the sun?

2. What source of heat was the radiometer exposed to, when outdoors?

[Type text]

Discussion and Explanation Discussion Item 1: The following points explain heat transfer through radiation  Heat transfer from the sun to the earth/to us takes place by the process of thermal radiation.  Thermal radiation is electromagnetic radiation generated by objects that have a temperature above zero kelvin.  If the learners are not familiar with electromagnetic radiation – you can instead use the term energy waves.  Light waves are an example of electromagnetic radiation.  We humans also generate thermal radiation but its intensity is very less, since our body temperature is not high.  The sun on the other hand, has a temperature of about 6000°C. It emits a large amount of thermal radiation. Some of this radiation is in the form of light waves.  When an object absorbs this thermal radiation, it is absorbing energy. Since energy causes the molecules in the object to vibrate faster, resulting in higher thermal energy. Hence, the temperature of the object increases.  Thermal radiation does not require a medium to travel, and can travel through vacuum.

Discussion Item 2: The following points are about the radiometer  The black and white blades of the radiometer are enclosed in vacuum. This means, heat cannot be transferred through conduction or convection to the blades.  When placed in sunlight or near any light, the blades rotate in the direction faced by the bright sides. This rotation is due to the fact that a black surface absorbs and radiates heat while a bright surface reflects heat. The greater heating of the blackened surfaces, according to one theory, causes nearby air molecules to move more rapidly and strike more blows on the darkened faces. i  When the radiometer was placed indoors, due to very low thermal radiation energy in the environment, the blades did not rotate.

KEY MESSAGES  

The sun’s heat reaches us through thermal radiation.

This radiant energy is absorbed by the vanes, which tend to rotate.

LEARNING CHECK We use kerosene as a fuel for the stoves in our home. But some people cook rice through solar cookers. On what fuel do these cookers work?

Answer for Instructor’s reference: A solar cooker works purely with heat energy (thermal radiation energy) from the sun.

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ABL 8.2

Time: 25 min

LEARNING OBJECTIVE – The response of black and white objects exposed to thermal radiations.

Note to Instructor – This activity requires 20 minutes incubation in the sun. You can do another activity with the learners while you wait like the Radiometer activity in 8.1.

If time permits, you can perform the burning of paper using a magnifying glass to show an example of radiation. (Refer ABL 1 in Handbook P4 – Light) ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Black tin

1 per class

2

White tin

1 per class

3

Thermometers

2 per class

4

Water

500ml per class

Things to do This activity requires two tins of equal size. One should be painted black and the other white, as shown in figure below.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity We know that heat reaches us from the sun through the process of radiation. Now we will see if the color of an object affects its ability to absorb this radiation.

Procedure Fill the two tins with equal amount of water.

Place one thermometer in each tin.

Keep both the tins outside in sunlight and record temperature every minute for 10 minutes.

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Figure 18: Radiation experiment

UNDERSTANDING THE ACTIVITY Leading questions 1. Is there any difference in the final temperature of the water in both tins?

2. Is there a difference in the how fast the temperature was increasing?

Discussion and Explanation Discussion Item 1: The following points relate colour to thermal radiation.  White light is a form of electromagnetic wave that has all the colors. Each color wave is unique since it has a different frequency.  When an apple appears red, it is because the apple is reflecting the red waves in the light and absorbing all other waves. If there was no light present in the room, you cannot see the apple as red, since there is no light for it to reflect.  When an object appears white, it means the object is reflecting all the waves in the light.  On the other hand, when an object appears black, it means the object is not reflecting any waves, and in instead absorbing all the waves.  So, a black object absorbs more light waves than a white objects. We learnt that light waves have some energy, and hence these waves also have thermal energy.  So, a black object absorbs more thermal energy, whereas a white object in comparison reflects more thermal energy.  This is why the black tin got warmer than the white tin.

KEY MESSAGES 

Darker colours absorb more thermal radiation than lighter colours.

LEARNING CHECK On a hot and sunny day, is it better to wear a white T-shirt of a black T-shirt?

Answer for Instructor’s reference: It is better to wear a white T-shirt is you want to feel more comfortable.

The white T-shirt will reflect more heat (or absorb less heat) than a black T-shirt.

TRY IT YOURSELF Light a candle, with the supervision of an elder. Put a metal spoon in the candle flame. After some time, your fingers touching the spoon will feel hot. Next, place your hand above the flame, this too would feel hot. Next, place your hand at the side of the flame. Can you tell which types of heat transfer you were experience in each case?

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INTERESTING INFORMATION Some animals, like snakes, can see in the dark by sensing infrared light. Rescue workers use infrared sensors to find people in emergency situations.ii Greenhouses are glass structures, typically the size of a big room, that are mainly used in cold places to grow plants that require warmer conditions.

iii

WEB RESOURCES http://blogs.toorakcollege.vic.edu.au/georgiaf1/ - Image for spiral paper – convection experiment. http://science.howstuffworks.com/dictionary/physics-terms/radiometer-info.htm - Explanation on radiometer http://www.youtube.com/watch?v=Atnjo7dD_bA – conduction, convection and radiation explained in a simple way. (Same video as in ABL 7)

VOCABULARY Convection: The transfer of energy between an object and its environment, due to fluid motion.

Radiation: The transfer of energy to or from a body by means of the emission or absorption of electromagnetic radiation.

Electromagneticradiation:A kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.

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ABL 9 - Methods of Mixtures Activity

Learning objective

Key messages

Time (min)

9.1

a) What happens when a hot liquid is mixed with a colder liquid? b) Determination of Specific heat of a solid ( Additional activity)



Heat flows from the hot liquid to the cooler liquid until both reach the same temperature.



The specific heat of the material can be found using the principle of calorimetry by the following formula:



60

Unit of the specific heat ………..j/kgÀ/0c

Total:

60

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INTRODUCTION When two substances at different temperatures are mixed, the amount of heat lost by the hot substance equals the amount of heat gained by the cool substance until thermal equilibrium is achieved - assuming no heat is lost to the surroundings.

Heat lost by hot body = heat gained by cooled body Once thermal equilibrium is achieved the temperature of the substance is between the initial temperature of the hot substance and cold substance.

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Time: 10 min

ABL 9.1a LEARNING OBJECTIVE – What happens when a hot liquid is mixed with a colder liquid?

ADVANCE PREPARATION Material List S.NO

Material

Required Quantity

1

Beaker with 300 ml hot water

1 per class

2

Beaker with 300ml

1 per class

cold/normal water 3

Empty Beaker

1 per class

4

Thermometer

1 per class

Things to do Heat water in the first beaker and keep it ready before the class starts.

Keep the three beakers on the table.

Safety Precautions Not Applicable

SESSION Link to known information/previous activity So far we have seen the effects of heat, and we know that when there is a source of heat energy, an object can get heated. Now we will reintroduce the idea of heat flow.

Procedure Ask three learners to come to the table.

Ask the first learner to measure the temperature of hot water in first beaker and write it on the board (t10C).

Ask the second learner to measure the temperature of cold water in second beaker and write it on the board (t20C) Agastya International Foundation. For Internal Circulation only.

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Ask the third learner to pour equal amounts of water from the first and second beaker into the third beaker, quickly stir the mixture and then measure the temperature of the mixture and write it on the board (t30C).

UNDERSTANDING THE ACTIVITY Leading questions 1. Why do we observe a high temperature for water in beaker 1 and a lower temperature for water in beaker 2?

2. What happens to the temperature when hot water and cold water are mixed in beaker 3?

3. Why should the temperature of the mixture behave that way?

4. What is happening when hot water is mixed with cold water?

5. What do you observe if the temperature is measured for a long time after mixing?

Discussion and Explanation Discussion Item 1: The following points are about the transfer of heat from hot water to cold water.  The water in beaker 1 was heated by some source to make it hot. Heat is transferred from the source (mostly fire from a spirit lamp) to the water.  The water in beaker 2 is either at room temperature or cold. If it is cooler than room temperature, it must have probably been cooled in a fridge.  Water was first poured into beaker 3 from beaker 1; it had the same temperature as beaker 1.

When we added cold water to it, heat was transferred from the hot water to the cold water added.  The transfer of heat continued until all water was at the same temperature. When the water has uniformly the same temperature, it is said to be in thermal equilibrium.  The temperature t3 would be greater than t1 and less than t2. This temperature remains steady for some time.

KEY MESSAGES 

Heat flows from the hot liquid to the cooler liquid until both reach the same temperature.

LEARNING CHECK While taking a bath, if the water is too hot, what do you do?

Answer for Instructor’s reference: There are two approaches we typically take for this problem. The first is – we add some normal/cold water to the hot water until the desired lower temperature is reached. Here heat is transferred from the hot water to the normal/cold water. The second – we wait for some time and the water cools down. Here heat is transferred from the hot water to the air around.

ABL 9.1b Agastya International Foundation. For Internal Circulation only.

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Determination of Specific heat of a solid Note to Instructor : This is an additional activity.

Materials: metal ball, test tube, beaker, water in a vessel, spirit lamp, spring balance and match box.

Procedure:  With the help of the spring balance find the mass of dry and empty test tube(w1)  fill 2/3 test tube with water and find the mass again (w2)  Insert a thermometer into the water in a test tube and note down the temperature (t1)  Find the mass of the given solid metal ball(w3)  Put the metal ball in to water in the beaker and start heating  When the temperature is around 900 C, record the temperature and transfer the metal ball in to the water in the test tube.(t2)  Observe the temperature in the test tube and record the highest temperature of the mixture(t3)  Cg- Specific heat of Glass  Cl – specific heat of water

Result / Key Message We can calculate the specific heat of material of the ball using the formula

Unit of the specific heat ………..j/kgÀ/0c

Heat – Student Observation sheet – 1 Agastya International Foundation. For Internal Circulation only.

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1. Activity 1.1 Beaker

Column 1 How do you feel when you dip your finger?

Beaker A Beaker B Beaker C

2. Activity 1.3b Write five hot objects and five cold objects, which you come across in day to day life Column 2 S.NO Hot objects Cold objects 1 2 3 4 5

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Heat – Student Observation sheet – 2

3. Activity 2.2 Individual activity

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OBSERVATION SHEET 3 - Find the temperature for each thermometer

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4. Activity 2.3b Individual activity

Conversion between scales: Celsius to Fahrenheit Fahrenheit to Celsius Celsius to Kelvin Kelvin to Celsius

0

F = 9/5 0C + 32 0 C = (0F – 32) 5/9 K = 0C + 273 0 C = K – 273

Perform the conversions and fill in the blanks: 500C = _____________ K 500C = _____________ 0F

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ihttp://science.howstuffworks.com/dictionary/physics-terms/radiometer-info.htm iihttp://beyondpenguins.ehe.osu.edu/issue/keeping-warm/cool-facts-about-heat iiihttp://www.thediygreenhouse.com/how-do-greenhouses-work/

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