Chapter 1 Introduction to Science 1 1.1 What is Science? 1.2 Science Laboratory 1.3 Steps in Scientific Investigation 1.4 Physical Quantities and their Units 1.5 The Concept of Mass 1.6 Measuring Tools 1.7 The Importance of Standard Units Mastery Practice
2 3 6 9 10 11 15 17
Chapter 2 Cell as a Unit of Life 21 2.1 Understanding Cells 2.2 Unicellular and Multicellular Organisms 2.3 Cell Organisation in the Human Body 2.4 Diffusion and Osmosis in Cells Mastery Practice
22 27 28 33 36
Chapter 3 Plants 40 3.1 Photosynthesis 3.2 The Transport System in Plants 3.3 The Sexual Reproductive System of Flowering Plants 3.4 Pollination 3.5 The Development of Fruits and Seeds in Plants 3.6 The Germination of Seeds 3.7 Application of Vegetative Reproduction in Flowering Plants 3.8 Stimuli and Responses in Plants 3.9 Biotechnology Mastery Practice
41 45 49 50 52 54 56 57 61 65
Chapter 4 The World through Our Senses 69 4.1 Sensory Organs 4.2 Sense of Touch 4.3 Sense of Smell 4.4 Sense of Taste 4.5 Sense of Hearing 4.6 Sense of Sight Mastery Practice
iv
Science Mathayom 1
70 72 74 74 76 78 82
Chapter 5 Matter 85 5.1 Matter 5.2 Properties of Matter 5.3 States of Matter 5.4 Classification of Matter Mastery Practice
86 88 89 94 95
Chapter 6 Simple Machine 98 6.1 Lever 6.2 Appreciating Innovative Efforts in the Design of Machines to Simplify Work Mastery Practice
99 102 104
Chapter 7 Sources of Energy 106 7.1 The Various Forms and Sources of Energy 7.2 Renewable and Non-renewable Energy Sources 7.3 The Importance of Conserving Energy Resources Mastery Practice
Chapter 8 Weather
107 113 117 120
124
8.1 What is Weather? 8.2 Factors of Weather 8.3 Cloud Formation and Types of Cloud 8.4 Measuring Rainfall 8.5 Monsoons, Tropical Cyclones and Thunderstorms 8.6 How to Avoid Danger during Severe Weather 8.7 Interpreting Weather Forecasts and Their I mportance Mastery Practice
125 125 126 128 129 130 130 133
Chapter 9 Global Warming
135
9.1 Global Warming 9.2 Causes of Global Warming 9.3 The Effects of Global Warming Mastery Practice
136 136 137 139
Contents
v
1
Introduction to Science
By the end of this chapter, you should be able to • understand what science is. •
name the common laboratory apparatus and their uses. • explain the hazard warning symbols. • observe the steps in a scientific investigation. • understand the typical quantities and their units. • understand the concepts of mass • know how to use measuring tools.
W h a t is S c ie n c e ?
Chapter 1 Introduction to Science
1
1.1
What is Science?
We see various natural phenomena in our daily life. Natural phenomena are things that happen in nature. Lightning, rainbows, the melting of ice, the growth of a baby into an adult and the fall of a ball to the ground are a few examples of natural phenomena. We want to know why and how all these things happen. We search for answers. The study of science gives us the answers. Science is the systematic study of nature and how it affects us and our environment. The information produced from the study of science is known as scientific knowledge. Scientific knowledge develops as new scientific discoveries are discovered every day. Using scientific knowledge, we invent many useful devices such as light bulbs, telephones and computers. The application of scientific knowledge for the use of mankind is called technology. We use technology in almost every aspect of life thus, making science part of our everyday life.
Importance of science Science plays important roles in our daily life. Here are some examples: (a) Science helps us to understand ourselves. Knowing how our body works, helps us to take better care of our health. (b) Science also helps us to understand our environment. This helps us to improve the quality of our environment and conserve it for our future generation. (c) Science makes our life more comfortable. We invent various machines to help us to work faster and more efficiently.
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  Science  Mathayom 1
The figure below briefly describes how science benefits us in various fields. In homes
Communication
• Facilities such as electricity and tap water make life easier and more comfortable. • Various appliances such as washing machine, microwave oven and vacuum cleaner help us to do our housework faster.
• Communication is easier and faster with the use of television, telephone, mobile phone, facsimile and computer. • Global communication is now possible with the use of communication satellites, e-mail and the Internet.
Transportation
Construction
• Transportation is easier, faster and more comfortable. • Modern public transport such as commuter trains and light rail transit reduce congestion in cities. • The design of better roads and highways increases the safety of users.
• Buildings and structures are now built with strong materials such as steel, concrete and reinforced glass. • Powerful machinery such as cranes, tractors and bulldozers are usually used in construction work.
Agriculture
Medicine
• Machines are used to carry out heavy and difficult tasks such as ploughing and harvesting. • Plant breeding, new agricultural techniques, fertilisers and insecticides contribute greatly in increasing the world’s agricultural products.
• More diseases can now be cured with the discoveries of new drugs, vaccines, antibiotics and the invention of better surgery techniques and equipment. • Diseases can be diagnosed and detected earlier with various tests and devices such as the X-ray machines and ultrasound scanning devices.
Uses and benefits of science in daily life
Chapter 1 Introduction to Science
3
Careers in science Science offers various career opportunities according to one’s area of interest. Listed below are a few examples: (a) Doctor A person who has been trained in and practises medicinal science. (b) Veterinarian An animal doctor. (c) Pharmacist A person who dispenses medicinal drugs and advises on their uses.
(d) Engineer A skilled person who designs, builds or maintains engines, buildings, bridges or roads. (e) Architect A person who designs buildings and advises on their construction. (f) Chemist A person trained in chemistry.
Science is divided into a number of areas of study, namely (a) Biology The study of life. (b) Physics The study of matter, energy, force and motion. (c) Chemistry The study of the composition and chemical properties of substances.
(d) Astronomy The study of planets and stars in the universe. (e) Geology The study of rocks, minerals and the structure of the Earth. (f) Meteorology The study of weather and climate. (g) Biochemistry The study of chemical processes in living organisms.
1.1 Q1. What is the difference between ‘science’ and ‘technology’? Q2. Give one benefit of science in the following areas. (a) Medicine (b) Transportation Q3. State the field of science related to the following. (a) Discovering a cure for cancer. (b) Studying the behaviour of insects. (c) Forecasting natural disasters such as floods and tornadoes. (d) Discovering new comets. Q4. List three careers that deal with human health.
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Science Mathayom 1
1.2
Science Laboratory
The place where a scientist works is called a laboratory.Students carry out scientific investigations or experiments during science lessons in science laboratories. We need to use apparatus to carry out experiments. The figure shows some common laboratory apparatus and their uses.
Test tube
• To hold small amounts of liquids or chemicals
Boiling tube
• For heating small amounts of liquids
Conical flask
20
20
20
15
15
15
10
10
10
5
5
5
Beaker
Flat-bottomed flask
• To hold bigger amounts of liquids or chemicals
10
9
100
8
7
6
5
4
3
2
1
0
Measuring cylinder
• To measure volumes of liquids
Filter funnel
• Used together with a filter paper to filter mixtures of solids and liquids
Evaporating dish
• To hold liquids for evaporating
Pipette
• To measure a fixed volume of liquids
Bunsen burner
• To provide a flame for heating
Crucible
• To hold solids for strong heating
Burette
Retort stand
• To measure small volumes of liquids accurately
• To hold or support apparatus
Tripod stand
Wire gauze
• To support apparatus during heating
• To support apparatus and ensure even heating
Test tube holder
Spatula
• To hold a test tube during heating
• To transfer small amounts of solids
General laboratory apparatuses and their uses
Chapter 1 Introduction to Science
5
Symbol
Danger of substances
Examples
Explosive • Easily explodes when mixed with other substances.
• Sodium, potassium
• Keep in paraffin. • Avoid contact with water.
• Concentrated acids and alkalis
• Keep away from other substances including water.
Flammable or inflammable • Easily catches fire and burns.
• Organic solvents such as ethanol, petrol and kerosene
• Keep away from fire or heat sources.
Toxic/poisonous • Causes death or harm to the body if absorbed through the skin, swallowed or inhaled.
• Mercury, chloroform, lead, benzene, bromine, sodium cyanide, hydrogen sulphide
• Do not inhale, touch or taste the substances. • Keep in a locked cupboard.
Corrosive • Causes damage to the skin or eyes upon contact.
• Concentrated acids and alkalis, bromine, hydrogen peroxide
• Avoid contact with skin or eyes. • Spill on body parts should be washed away quickly under running water.
Irritant/harmful • Irritates (causes itchiness and rashes) skin, eyes and respiratory system.
• Ammonia solution, chloroform, dilute acids and alkalis
• Spill on body parts should be washed with a lot of water.
Radioactive • Gives out radiation that can cause cancer or destroy bodily tissues.
• Uranium, plutonium, radium
• Keep in special lead containers.
Hazard warning symbols
8
Handling techniques
Science Mathayom 1
Identifying the problem • First, we determine what we want to find out. • In order to do so, we need to observe things or happenings carefully to obtain information. Based on our observation, we then ask questions about the things or happenings.
Forming a hypothesis • To make a smart guess to explain the problem. • The hypothesis has to be tested based on the evidence collected.
Planning an experiment This section involves: • Identifying the variables involved. A variable is a condition that influences the results of the experiment. • Determining the materials and apparatus required. • Determining the procedure to carry out the experiment, methods of collecting and analysing data.
Carrying out the experiment This section involves: • Controlling the variables as planned so that the experiment is a fair test. • Collecting data through observations and measurements. All these must be done systematically, accurately, objectively and honestly.
Analysing and interpreting data • Explaining the collected data in an objective and logical manner. • Giving an explanation about the pattern or relationship based on the data collected.
Making a conclusion • State whether the hypothesis is true. • A conclusion should be made based on the data and not influenced by any unfair opinion.
Writing a report on the experiment • Present the aim, materials, apparatus and procedures, any table or graph and conclusion clearly in the report. • It is important as a means of communication among scientists.
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Science Mathayom 1
e r im e n
t
Ex p
An example of a science report is given below. Investigating the relationship between the length of a pendulum and the period of oscillation
Problem: How does the length of the pendulum affect the time of oscillation? Hypothesis: The longer the length of the pendulum, the longer the period of oscillation. Constant variable: Weight of the pendulum Manipulated variable: Length of the pendulum Responding variable: Period of oscillation Materials/apparatus: String, cork, wooden block, retort stand with clamp, stopwatch and metre rule. Procedure: 1. A simple pendulum of 20 cm in length is String Length of made as shown in the figure on the right. Retort pendulum stand = 20 cm 2. The time taken for the pendulum to make 20 oscillations is recorded. P Q Reminder
Wooden block
One full oscillation of a pendulum is the movement of the pendulum from P to Q and back to P again.
A simple pendulum
Length of Time taken for pendulum 20 oscillations (cm) (s) 20 16 40 25 60 31 80 36 100 40
Time taken for one oscillation (s) 0.8 1.3 1.6 1.8 2.0
Time taken to complete one oscillation (s)
3. The experiment is repeated using the pendulum at lengths of 40 cm, 60 cm, 80 cm and 100 cm. 4. Results are recorded in a table and a graph of the time taken to complete one oscillation against the length of the pendulum is plotted. Results:
Length of pendulum (cm)
Graph of time taken to complete one oscillation against the length of the pendulum
Discussion: From the graph in the above figure, the time taken for one oscillation increases as the length of pendulum is increased. Conclusion: The longer the length of the pendulum, the longer the period of oscillation. The hypothesis is accepted.
Chapter 1  Introduction to Science 
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1.5
The Concept of Mass
Weight The Earth pulls all objects to its centre. This pull is called the force of gravity or gravitational force. The weight of an object is the pull of the Earth on the object. The weight of an object can change. It depends on the gravitational force that acts on the object at that place. Because of this, the weight of an object differs from place to place. The weight of an object becomes less when the object is further away from the centre of the Earth. Thus, it is less on top of a high mountain than at sea level. The weight of an object is measured using a spring balance or a compression balance. The SI unit for weight is Newton (N). J
Scale
S BA PR LA IN N G C 0 E 1 2 0 3 10 4 0 2 0 5 30 0 6 0 40 7 50 0 8 60 0 9 70 0 10 80 0 90 0 10 0 00
Disc
Scale
Hook A spring balance
A compression balance
Weighing devices
Mass The mass of an object is the quantity of matter contained in the object. Unlike weight, the mass of an object is constant everywhere. This is because the quantity of matter in an object is the same wherever the object is. The mass of an object is measured using a lever balance, a beam balance or an electronic balance. The SI unit for mass is the kilogram (kg).
Chapter 1  Introduction to Science 
15
1.7 Q1. State two problems of having different standard units for a physical quantity. Q2. Other measurement units are still being used in certain parts of the world. These units can be converted to the SI units and vice versa. Solve the following problems. (a) You have bought 5 yards of cloth in another country. What is the length of this cloth in metres? [Hint : 1 yard = 0.91 m] (b) You need two kilograms of sugar. How much is it in pounds? [Hint : 1 pound = 0.45 kg]
Natural phenomena
Uses & benefits
Careers
What is science? Steps in scientific investigations • • • •
Identifying the problem Forming a hypothesis Planning an experiment Carrying out the experiment • Analysing/interpreting data • Making a conclusion • Writing a report
Length • Metre rule
Current • Ammeter
Introduction to Science
Mass Concept of mass and weight
Differences Weight
Physical quantities & units
Physical quantity
Measuring tools
Time • Stopwatch
SI Unit
Length
Metre (m)
Current
Ampere (A)
Time
Second (s)
Temperature
Kelvin (K)
Mass
Kilogram (kg)
Temperature
Mass
• Thermometer
• Lever balance
Weight • Spring balance
Volume • Measuring cylinder
Chapter 1 Introduction to Science
25
Fill in the blanks with the given words time (t) spring balance forming a hypotesis same making conclusion technology physical mass (m) Newtons Ampere (A) metre (m) rules science gravity safety precautions metre (m) kelvin (k) 1.
is the systematic study of nature and how it affects us and our environment.
2.
is the application of scientific knowledge for the use of mankind.
3. Students must follow the in the laboratory.
and
to avoid accidents
4. The sequence of steps involved in a scientific investigation are identifying the problem; ; planning an experiment; carrying out the experiment; analysing and interpreting data; ; and writing a report on the experiment. 5. A unit.
quantity is a quantity that can be measured. It is measured in SI
6. The basic physical quantities are: Physical quantity (symbol) (a)
SI unit (symbol)
Length (l)
(b)
kilogram (kg)
(c)
second (s)
(d)
Temperature (T)
(e)
Electric current (l)
7. The differences between mass and weight: Mass
26
Weight
(a)
The amount of matter contained in an object.
The force of on an object.
(b)
Remains the places.
Changes according to places.
(c)
Measured in kilograms.
Measured in
(d)
Measured with a lever balance or a beam balance.
Measured with compression balance.
  Science  Mathayom 2
at all
acting
. or a
5. Which of the following pairs is not matched correctly?
Objective Questions 1. Which of the following statements is true of science? A Science helps us to solve all problems. B Science can only be studied in laboratories. C Science is an understanding of natural phenomena. D Science enables us to know the past and the future. 2. Which of the following are phenomena? I Air pollution II The ripening of a fruit III The formation of clouds IV The germination of a seed A III and IV only B I, II and III only C II, III and IV only D I, II, III and IV
Field A Agriculture
Increase in food production
B Transportation More road accidents C Medicine
More successful surgeries
D Education
Better teaching equipments
6. Figure 1 shows how a student heats up a beaker of water. Beaker
natural
3. The following describes X, a science-related profession. X manipulates organisms to make products that benefit human beings. For example, producing new antibiotics or new biodegradable materials.
Water
Bunsen burner Tripod stand
Figure 1
After some time, the beaker cracks and the water leaks out. What mistake has he done? A The beaker is too small. B A taller tripod stand should be used. C The flame of the Bunsen burner is too strong. D A wire gauze should be put below the beaker. 7. Methanol has the following characteristics.
X is most probably A a chemist C an astronomer B a pharmacist D a biotechnologist 4. P, Q, R and S are steps in lighting a Bunsen burner. P – Q – R – S –
Contribution of science
Light up the match Turn on the gas Open the air-hole Close the air-hole
The correct sequence to light the burner is A R → P → Q → S B R → Q → P → S C S → P → Q → R D S → Q → P → R
• Burns easily • Can cause death if swallowed.
Which hazard warning symbols are found on the labels of bottles containing methanol? I
III
II
IV
A I and II only B I and III only
C II and III only D I, II and III only
Chapter 1 Introduction to Science
27