POLARIS CHEMISTRY
VWO / GYMNASIUM
SCHOOL YEAR 3
METHOD CONCEPT / EDITOR
Boom voortgezet onderwijs
AUTHORS
Ricardo Dekker
Jurjen Draaisma
Boukje Gijsberts
Nanda Koops
Paulien van der Meulen
Michel Wijnhold
POLARIS CHEMISTRY
VWO / GYMNASIUM
SCHOOL YEAR 3
BOOM VOORTGEZET ONDERWIJS
1 Substances
1.1 Chemistry and practicals 8 1.2 Pure substances and mixtures 14 1.3 Separating mixtures 1 20 1.4 Separating mixtures 2 26 1.5 Calculating with mixtures 32
Test preparation 38
2 Chemical reactions
2.1 Chemical reactions 42
2.2 The periodic table 48
2.3 Chemical equations 54
2.4 Decomposition reactions 60
2.5 Combustion reactions 66
Test preparation 72
3 Chemical bonds
3.1 Classification of substances 76
3.2 Metals 82
3.3 Molecular substances 88
3.4 Salts 94
3.5 Calculation with solutions 100
Test preparation 106
4 Mass and energy
4.1 Mass and mass ratio 110
4.2 Atomic mass 116
4.3 Mass and chemical equations 122
4.4 Energy changes 128
4.5 Calorific value 134
Test preparation 140
5 Chemistry and life
5.1 Nutrition 144
5.2 The carbon cycle 150
5.3 The nitrogen cycle 156
5.4 Water quality 162
5.5 Green chemistry 168
Test preparation 174
6 Chemical industry
6.1 Processes in the chemical industry 178
6.2 Rate of reaction 184
6.3 Polymers 190
6.4 Soap 196
6.5 Hydrogen 202
Test preparation 208
Reference
A Practical
A1 Safety 212
A2 Burner 213
A3 Practical report 214
B Substances
B1 Elements 215
B2 Properties of substances 216
B3 Names and formulas 217
B4 Systematic names 217
B5 Reagents 218
C Calculation
C1 Prefixes 219
C2 Powers of ten 219
C3 Converting units 220
C4 Converting compound units 221
C5 Equations 221
C6 Methods 223
D Experiments 224
E Design 226 Image credits 228 Register of terms 229
1 Substances
1.1 Chemistry and practicals 8
1.2 Pure substances and mixtures 14
1.3 Separating mixtures 1 20
1.4 Separating mixtures 2 26
1.5 Calculating with mixtures 32
Test preparation 38
1.1 Chemistry and practicals
L ea R n I n G GOa L You learn how to carry out chemistry practicals safely.
Chemistry How can you make concrete stronger, medicines better, food safer, and fuel more sustainable? These are questions that chemists are concerned with. Chemistry is therefore about substances, the properties of substances, and how substances react with each other. Substances are often investigated with experiments. At school, you carry out these experiments during the chemical practical.
Safety rules In a chemical practical, you often work with a burner and dangerous substances. A number of safety rules apply (Reference A1). You must always wear safety glasses and a lab coat. Follow the instructions, and think about whether the substances you are going to work with are dangerous before starting. To help you, there are international pictograms. Figure 1.1 shows some examples of these. Some experiments release harmful fumes. You (or the teacher or lab assistant (toa)) carry out these experiments in a fume cupboard. The dangerous fumes are extracted from the fume cupboard, so that you cannot inhale them. If you are unsure about something, always ask for help from your teacher or the lab assistant. After the experiment, tidy up all the items and materials used.
1 Corrosive
Explosive
Oxidizing
Health hazard 5 Environmental hazard
Toxic
Harmful/irritating
Flammable
Compressed gas
Glassware During experiments, you use laboratory glassware such as test tubes, conical flasks (also known as Erlenmeyer flasks), roundbottomed flasks, and glass beakers. It is important to use exactly the right quantities. There is special glassware with accurate graduations for this, such as a measuring cylinder or volumetric pipette (Figure 1.2).
The burner During the practical, you will often use a burner for heating or burning substances. The burner can make three different flames, which are used in different ways (Figure 1.3, Reference A2):
1 A yellow flame, which is also called a safety flame.
2 You use a pale blue flame to heat a substance gradually.
3 You use a roaring flame to heat a substance strongly.
Safety equipment There are various things in the practical lab to put a fire out. If a classmate’s clothing catches fire, put it out with a fire blanket. This stops oxygen from reaching the fuel. A fire extinguisher has the same effect. You can also extinguish a fire with water. Water cools the fuel. If you come into contact with corrosive or toxic substances during a practical, you can wash them away with the emergency shower. If you get a corrosive or toxic substance in your eyes, use the safety eye wash. It’s important you know where this equipment is located in the laboratory. If something goes wrong, always report it immediately to the teacher or lab assistant.
A structured practical When investigating something in a chemical practical, you work according to a fixed procedure:
First determine what you want to know or need to know. This is called the ‘research question’.
Check whether everything you need is in the laboratory.
Carry out the practical. Pay attention to the order that everything is done in.
During the practical, you make observations. Pay close attention to what you see, hear, and smell. Make notes of these as you go.
Draw a conclusion and answer the research question.
Put all your findings in a report. Reference A3 explains what needs to be in a report.
1.2 Types of glassware: 1: measuring cylinder, 2: volumetric pipette, 3: test tube, 4: conical flask, 5: glass beaker, 6: round-bottomed flask
1.3 The burner with three types of flame
Exercises
1 a What are the parts of a practical report? R
b Which glassware accurately measures the volume of a liquid? R
c Write down three different extinguishing agents. R
2 Figure A
You start with a white powder. You drip three drops of water onto it. A blue powder is formed. Write down any observations you make. T1
3 In an experiment, you have to heat a small amount of water in a test tube to 50 °C. Explain which flame you use for this. T1
4 Draw a floor plan of your school’s laboratory. Clearly indicate where the extinguishing agents are. T1
5 Figures B, C and D
Look at the pictograms.
a Write down the meaning for each pictogram. R
b For each pictogram, think of a substance that it could refer to. T1
6 You heat water in a glass beaker. First, you see little bubbles rising out of the water. A little later, you see that the water is boiling because large vapour bubbles rise from the water. Write down your observations and conclusions. T2
7 Measure 50 mL of water in a measuring cylinder. Then pour this into a glass beaker. There seems to be less than 50 ml in the beaker. What should you do? T1
a Fill up the water in the glass beaker to the 50 ml graduation mark.
b Throw the water away, and measure water in the measuring cylinder again.
c Nothing at all. You measured the water correctly.
8 Hexane is a liquid that is very similar to water, but with a lower density. Hexane does not mix with water and is highly flammable.
a Why shouldn’t you pour hexane down the sink? T2
b Explain why it would be dangerous to pour hexane down the sink. I
9 Figure E
Methanol, like water, is a colourless liquid. It’s a commonly used raw material in the chemical industry. It’s also used as a fuel.
a What should you take into account when using methanol? T1
b Explain whether you should carry out an experiment with methanol in the fume cupboard. T2
10 Someone online claims that you can clean copper coins with cola. Describe an experiment to find out which type of cola is most suitable for cleaning coins. I
11 Figure F
Take a good look at the picture. Name three things these students are doing wrong. T2
HOME EXPERIMENT
To measure a quantity, use a measuring beaker. The ones you have at home are not as accurate as the measuring cylinders at school. Place the empty measuring beaker on a scale, and set the scale to zero. Now add 500 ml of water to the measuring beaker. Does it weigh 500 grams? Try this more often if you have more than one measuring beaker.
Highly flammable liquid and vapour. Toxic by inhalation. Toxic on contact with skin. Toxic if swallowed. Causes damage to organs.
Keep away from heat/sparks/open flames/hot surfaces – do not smoke.
Store in a tightly-sealed container.
Wear protective gloves/protective clothing/eye protection/face protection. In case of contact with the skin, wash with plenty of soap and water. In case of exposure, immediately call the poison control centre or a doctor.
WHC 1 Mr 32.04
Methanol
CAS Number 67-56-1
Find out more
12 Read the text about explosion limits on the next page.
a The concentration of petrol in the air at a filling station is measured at 0.9%. Explain whether there is an immediate explosion hazard. T1
b An employee decides to temporarily close the filling station. Explain whether the risk of an explosion can increase. T1
c Why can’t a mixture explode if it is too rich? I
13 Online, it says that ethanol boils at 79 °C. You want to check this with an experiment.
a Formulate the research question for this experiment. T1
b Write down what you need for the experiment and how you will carry it out. I
c What safety precautions must you take for this experiment? I
14 A measuring cylinder is often narrow and tall, while a glass beaker, by contrast, is wide. Why do you think a measuring cylinder is so tall and narrow? I
Have you achieved the learning goal?
R I know the meaning of the following terms:
Safety glasses and lab coat
Pictogram
Fume cupboard
Test tube, conical flask, round-bottomed flask and glass beaker
Measuring cylinder and volumetric pipette
Burner
Yellow flame, pale blue flame and roaring flame
Fire blanket and fire extinguisher
Emergency shower and safety eye wash
T1 I can determine which flame is needed for an experiment.
T2 I can explain the difference between an observation and a conclusion.
I I can formulate a research question and think of a suitable experiment to test it.
Explosion limits Some substances are highly flammable and can explode. An explosion is a combustion reaction that releases a lot of energy very quickly (Figure 1.4). An explosion can only occur if the ratio between the amounts of fuel and air is between certain limits: the explosion limits of the fuel. Table 1.6 shows the explosion limits of a number of flammable substances. The explosion limit is expressed as the percentage of gaseous fuel in relation to the air. If there isn’t enough fuel, the mixture is said to be too lean. If there is too much fuel in it, the mixture is said to be too rich (Figure 1.5).
explosive range mixture too lean
mixture too rich
flammable liquid
flammable gas molecules oxygen molecules
1.6 Explosion limits of various substances. Percentage relative to air.
1.4 An explosion often causes a fire.
1.5 The upper and lower limits for explosive gas mixtures
1.2
Pure substances and mixtures
L ea R n I n G GOa L You learn the difference between pure substances and mixtures.
Pure substances and mixtures Chemistry is all about substances. Water, air, plastic, grease, wood and chalk are all examples of substances. There are two types of substances: pure substances and mixtures. Sugar, salt and iron are examples of pure substances. Air is an example of a mixture. This mixture includes the substances oxygen and nitrogen. Tap water is also a mixture. It contains, for example, calcium salts. Most substances in everyday life are mixtures of two or more pure substances.
Substance properties Characteristics which identify a substance are called substance properties. For example, sugar and table salt are both white substances that dissolve in water. However, they differ in taste: sugar is sweet, table salt is not. So they have the same colour and comparable solubility, but a different taste. Colour, solubility and taste are substance properties. Other examples of substance properties are boiling point, density, electrical conductivity, and flammability.
Molecules If you break a sugar cube in half, it’s still sugar. If you break the half in half again, the remainder is still sugar. You can keep doing this until you have only one particle of sugar. This smallest sugar particle is called a sugar molecule. If you break a sugar molecule, however, it’s not sugar anymore. Molecules are therefore the smallest particles of a substance.
Macro level and micro level You can look at substances in two ways: at macro level and at micro level. When you examine at a substance at the macro level, you look at the properties of the substance that you can perceive with your senses. For example: sugar water is liquid, tastes sweet, and is transparent. Macro means large. If you describe sugar water in terms of molecules, you’re referring to the micro level. Micro means very small. In chemistry, the micro level is often used to explain observations at the macro level.
Three phases of substances The substance water exists in three different forms: solid (ice), liquid (water) and gas (water vapour). These different forms are called the phases of water. Each of these three phases involves the same water molecules. Substances can occur in three phases: solid (s), liquid (l) and gas (g). You can explain the properties of the three phases at a micro level. This is shown in Figure 1.7. In the solid phase, the molecules vibrate close to each other in a fixed position and attract each other strongly. In the liquid phase, the molecules move around close to each other. Although the molecules still attract each other, the overall shape of the substance is not fixed in this phase. In the gas phase, the molecules move far apart, and hardly attract each other at all.
Phase transitions When ice melts, it becomes a liquid. Here, water changes from the solid phase to the liquid phase. The change of a substance from one phase to another is called a phase transition. Melting is therefore a phase transition. The reverse of melting is freezing/solidification. The other phase transitions are: evaporation (liquid gas), condensation (gas liquid), deposition (gas solid) and sublimation (solid gas).
Melting and boiling points, melting and boiling ranges
The temperature of a pure substance does not change during melting or boiling. This is shown in Figure 1.8a. The graph plots the temperature of a pure substance against time. Pure substances have a melting point and a boiling point. These are both substance properties. If a mixture is heated, on the other hand, the temperature changes when it melts. A mixture therefore has a melting range and a boiling range instead of a melting point and boiling point (Figure 1.8b).
1.7 The three phases at micro level
1 the solid phase
2 the liquid phase
3 the gas phase
Exercises
15 True or False? Explain your answer. R
a There is only one type of molecule in a pure substance.
b If you break a sugar cube, it isn’t sugar any more.
c Water vapour and ice contain different molecules.
d The phase transition from solid to gas is called sublimation.
16 Figure A
The paper clips all have the same shape and size. You can change their shape because paper clips are flexible. However, they all have a different colour. Explain which of the above properties are properties of the substance the paper clips are made of. T2
17 a What phases can a substance have? Include the abbreviation. R
b Which substance properties determine the phase of a substance at room temperature (20 °C)? T1
c What phase is sugar in at room temperature? T1
d Hexane has a melting point of −95 °C and a boiling point of 69 °C. Which phase is hexane in at 20 °C? T2
18 Make two columns: ‘Pure substance’ and ‘Mixture’. Put each of the following substances in the correct column: sugar, sugar water, hexane, salt, milk, cola, air, starch. T2
19 Give the phase transitions for the following examples. T1
a Your glasses misting up.
b Washed clothes drying.
c You exhale in winter and see a cloud.
20 a Name three substances that you think are mixtures. T1
b Why do you think these substances are mixtures? T2
21 Make a micro-level drawing of sugar water, a solution of sugar in water. Show a molecule as a sphere. T2
22 A substance can have a melting point and a boiling point or a melting range and a boiling range.
a What happens to the temperature when a pure liquid boils? T1
b What happens to the temperature when a mixture melts? T1
c Explain whether wine has a boiling point or a boiling range. T2
23 a Why can’t you use tap water in chemistry if you need water for an experiment? T1
b Think of an experiment where you could use tap water. I
24 Flour and milk powder are two different substances that seem very similar.
a What substance property do they have in common? T1
b In which substance properties do they differ? T1
c How could you find out, without tasting, whether there is flour or milk powder in a jar? I
25 Figure B
Copy the numbers, and put the correct phase or phase transition next to each number. R
26 Figures C, D, E and F
Four models of substances are shown above. For each model, indicate whether it concerns a model of a pure substance or a mixture. Also indicate the phase. T1
27 Oil and water do not mix. If you try to mix them, the oil floats on the water. This is because the oil molecules cannot mix well with water molecules. Instead, separate oil and water layers are formed.
a Which sentence or sentences relate to the macro level? T2
b Which sentence or sentences relate to the micro level? T2
28 For each statement, explain whether it relates to the micro level or macro level. T1
a In a liquid, the molecules are closer together than in a gas.
b The boiling point of alcohol is 79 °C.
c Household vinegar is a clear mixture of acetic acid and water.
HOME EXPERIMENT
At home, you use mixtures and pure substances. Find three mixtures at home and take a photo of each. Also say which substances each mixture contains.
Find out more
29 Read the text about reinforced concrete on the next page.
a Which properties of the concrete and which properties of the steel can be used in construction? T2
b Why do structural engineers want to combine the properties of concrete and steel? T2
c Give an example of another composite material. Which substances are used to make this material? I
d What properties are combined in the material you gave as an example in Question c? T2
30 The composite material carbon fibre is increasingly common nowadays. It is based on the substance carbon.
a Name one use for carbon fibre. T1
In carbon fibre, the carbon takes the form of long fibres that are very strong and highly resistant to stretching. These fibres can be processed into various strong structures. The advantages of carbon is its low density and the property that it does not react with air or water.
b Why was carbon fibre chosen as the material in the example given in Question a. T2
c Give three reasons why carbon fibre is such a popular material. I
Have you achieved the learning goal?
R I know the meaning of the following terms:
Pure substance and mixture
Substance property
Molecule
Micro level and macro level
Solid, liquid and gas phases
Phase transition
Melting point and boiling point
Melting range and boiling range
T1 I can explain the difference between a pure substance and a mixture at the micro level and the macro level.
T2 I can distinguish between micro-level and macro-level descriptions.
I I can explain which substance properties I can combine to make a new material with new properties.
Reinforced concrete It can be useful to combine different materials. The properties of both substances are then exploited in the mixture. The construction sector makes extensive use of reinforced concrete. First, a steel framework is constructed. Construction workers then pour concrete around and inside it. They do this to combine the properties of the steel and the concrete. The reinforced concrete is much stronger due to the steel bars. Together, it forms a strong material that cannot easily crack or break.
1.9 Reinforced concrete is widely used in the construction of buildings and foundations.
1.3 Separating mixtures 1
L ea R n I n G GOa L You learn what mixtures are and how to separate them.
Solution, suspension and emulsion A mixture is a combination of two or more pure substances. There are three types of mixtures of a liquid with another substance that you need to know.
Solution: A clear mixture of different liquids, a solid and a liquid or a gas and a liquid. The liquid in which the other substances are dissolved is called the solvent. Cola is an example of a solution. In cola, solid sugar and the gas carbon dioxide, among other things, are dissolved in the solvent water.
Suspension: A cloudy mixture of a solid and a liquid. The mixture is cloudy because the solid floats as solid particles in the liquid instead of dissolving. A mixture of flour and water is an example of a suspension.
Emulsion: A cloudy mixture of two liquids. Small droplets of one liquid float in the other and do not dissolve. Milk and mayonnaise are examples of emulsions. To ensure that an emulsion stays well mixed, an additive is required. This type of additive is called an emulsifier. The emulsifier in mayonnaise is egg yolk.
Homogeneous and heterogeneous mixtures You cannot see the different substances in a solution. The mixture is uniform throughout. This type of mixture is homogeneous. In a suspension, you see the particles of the solid floating in the liquid. You can therefore distinguish the different substances in the mixture. Such a mixture is heterogeneous
You can explain this at the micro level as follows (Figure 1.10). In a homogeneous mixture, every molecule of one substance is surrounded by molecules of the other substance. In a heterogeneous mixture, there are separate groups of molecules of at least one of the substances in the mixture. An emulsion is therefore also a heterogeneous mixture.
Sedimentation If you leave a glass of freshly squeezed orange juice to stand for a while, a deposit forms at the bottom and the juice at the top becomes clearer. This is because the density of the solid is greater than that of the liquid. The difference in density causes the solid to slowly sink to the bottom. This separation method is called sedimentation. You can then pour the liquid layer off the solid to separate the two substances.
Centrifugation Blood is a suspension that contains, among other things, white and red blood cells. These blood cells can be separated from the blood plasma by sedimentation. This takes quite a long time. Spinning the blood around rapidly in test tubes accelerates sedimentation (Figure 1.11). This is called centrifugation. The blood particles with the highest density end up at the bottom of the tube. The blood particles with the lowest density remain at the top. Centrifugation is therefore a separation method based on the difference in density of the mixed substances.
Filtering To stop coffee grounds from ending up in your coffee, you use a filter. This separation method is called filtration. The liquid and dissolved substances pass through the filter, while the solid remains behind. This is because the solid particles are too large to pass through the filter. This method depends on a difference in particle size between the substances to be separated. The part that goes through the filter is the filtrate. The part that remains behind the filter is the residue (Figure 1.12).
1.11 Test tubes with blood in a centrifuge
1.12 Filtration funnel with paper filter residue filtrate
© 2020 Boom voortgezet onderwijs, Groningen, The Netherlands
Second edition, 2021
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Polaris is an RTTI-certified teaching method and distinguishes four types of questions:
R Remember questions
T1 Training questions
T2 Transfer questions
I Insight-innovation questions
For more information about the RTTI system, see www.docentplus.nl.
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Layout & technical drawings PPMP, Wolvega