1 Introducing Science 1-4

Transcription

1 1 Introducing Science 1-4 T hin k ing What is the difference between a discovery and an invention? Discoveries are the observation and explanation of the natural phenomena, while inventions are creations of new methods or devices. Activity Great scientists 1. C 2. D 3. A 4. B Activity The two sides of science Tim Cars can take us from one place to another quickly, but they cause air pollution in the environment. Joanne When drugs are used properly, they can cure diseases. The abuse of drugs may lead to health problems. Steven The internet can help people get information all over the world. However, some people are obsessed with the internet and may fail to develop communication / social skills.

2 2 Unit 1 Introducing Science TEST YOURSELF (a) What is science about? Science is the study of nature. (b) List three branches of science. Biology, chemistry, physics, geology, astronomy (any three) 2. Complete the following statements about the discoveries or inventions made by different scientists. (a) Galileo Galilei invented (invented / discovered) a telescope and discovered (invented / discovered) the four moons of Jupiter. (b) Sir Isaac Newton discovered (invented / discovered) the force of gravity. (c) Alexander Graham Bell invented (invented / discovered) the telephone. (d) Marie Curie discovered (invented / discovered) two radioactive elements. Activity Where does the mould come from? Tim used a scientific method to study a daily life problem. For Steps 1 to 5 below, identify the steps of the scientific investigation. Put your answers in the spaces provided. 1. Making observations 2. Asking a question 3. Suggesting a hypothesis 4. Testing the hypothesis 5. Drawing a conclusion T hin k ing 1-16 If you were Tim, how would you test the second hypothesis The mould on the bread comes from the air? Prepare two pieces of bread. Leave one piece exposed to the air and the other enclosed in a plastic bag. Examine them after a few days. If the second hypothesis is correct, the bread exposed to air will be covered with mould, while the bread not exposed to air will not be covered with mould.

3 Unit 1 Introducing Science 3 Activity How does temperature affect the growth of mould on bread? Tim s experiment: Is this a fair test? This is not (is / is not) a fair test. It is because the two set-ups are different in more than one (only one / more than one) condition(s). Steven s experiment: Is this a fair test? This is not (is / is not) a fair test. It is because the two set-ups are different in more than one (only one / more than one) condition(s). Doris experiment: Is this a fair test? This is (is / is not) a fair test. It is because the two set-ups are different in only one (only one / more than one) condition(s). TEST YOURSELF The scientific investigation consists of the following main steps: Making observations Asking a question Suggesting a hypothesis Testing the hypothesis Drawing a conclusion 2. Write T if the statement is true and F if the statement is false in each box provided. (a) Scientific knowledge is always true. (b) Science can solve all of our problems. (c) Scientists classify objects into groups according to their similar features. (d) In a fair test, the variable to be studied should be kept constant. F F T F

4 4 Unit 1 Introducing Science Activity Equipment in your school laboratory Look around your school laboratory. Can you find the following equipment? Write the names of the equipment in the spaces provided. 1. gas tap 2. sink and water tap 3. electric socket 4. first-aid box 5. fume cupboard 6. eye-wash bottle 7. fire extinguisher 8. fire blanket 9. sand bucket T hin k ing 1-26 What is the difference between a science laboratory and an ordinary classroom? A science laboratory is usually bigger and with laboratory equipment. An ordinary classroom is usually smaller and without laboratory equipment. (Accept other reasonable answers)

5 Unit 1 Introducing Science 5 Activity Equipment in your school laboratory 1. Which floor is your school's science laboratory located on? The science laboratory is located on. 2. Draw the layout of the science laboratory in the space below. Label the blackboard, benches, doors and the laboratory equipment using the symbols given below. (Depends on the environment of the laboratory.) Symbols teacher s bench and blackboard student s bench laboratory door fire extinguisher sand bucket fire blanket fume cupboard first-aid box 3. If there is an accident, how can you leave the laboratory safely? Use red arrows to mark the escape route on the layout.

6 6 Unit 1 Introducing Science layout. Activity Potential dangers in the laboratory Student(s) Potential danger Reason for the potential dangers Donald, Ken Playing and running in the laboratory D James Touching the electric plug and socket with wet hands B Chloe Not tying back long hair C Dora Pointing the mouth of the test tube towards others while heating A Emma Eating and drinking in the laboratory E Activity Coping with laboratory accidents What should you do if the following accidents occur? Link the accidents and the actions you should take. 1. Some chemicals are spilt on your hand. 2. Some chemicals get into your eye. Accident 3. You touch something hot and burn your finger. 4. You smell gas leakage. A. close the gas tap B. wash it with an eye-wash bottle Action C. wash the affected area with running water

7 Unit 1 Introducing Science 7 EXPERIMENT Studying the ways of putting out a fire Part A Using water 2. What happens to the flame? The flame goes out (remains unchanged / goes out). Part B Using sand 2. What happens to the flame? The flame goes out (remains unchanged / goes out). Part C Using carbon dioxide 2. What happens to the flame? The flame goes out (remains unchanged / goes out). Discussion Which component of the fire triangle is removed by 1. water? heat 2. sand? oxygen 3. carbon dioxide? oxygen T hin k ing 1-34 Which component of the fire triangle is removed in each of the methods shown in Fig. 1.24? Oxygen is removed in the three methods.

8 8 Unit 1 Introducing Science TEST YOURSELF Finish the following matching. 1. We usually conduct a scientific investigation in a D. 2. We should wear F while heating substances. 3. There are A on the containers of hazardous chemicals. 4. Fire extinguisher, sand bucket and B are some common fire-fighting equipment in the laboratory. 5. The three components of the fire triangle are fuel, C and heat. A. hazard warning symbols B. fire blanket C. oxygen D. laboratory E. carbon dioxide F. safety goggles G. classroom H. eye-wash bottle EXPERIMENT Transferring and mixing solutions 1. Note down the colour of each solution. Solution A B C Colour colourless clear blue colourless 5. Record your observations in the same table. Mixed solution Colour of the mixed solution Any solids formed at the bottom? Any bubbles released? A + B colourless no no A + C colourless no yes B + C pale blue yes no

9 Unit 1 Introducing Science 9 EXPERIMENT Lighting a Bunsen burner 4. Examine the flame of the Bunsen burner. Write down your observations in the table below: What is the colour of the flame? Is the flame regular or irregular in shape? Is the flame luminous or non-luminous? Is the Bunsen burner quiet or noisy? When the air hole is closed yellow irregular luminous quiet When the air hole is open blue regular non-luminous noisy EXPERIMENT Using a Bunsen burner for heating Part B Heating a solid 1. Record the colour of the solid. The colour of solid A before heating: 3. Record the colour of the solid. The colour of solid A after heating: blue white

10 10 Unit 1 Introducing Science TEST YOURSELF Link the following apparatus and their uses. Apparatus (a) dropper (b) reagent bottle (c) glass rod (d) safety goggles (e) Bunsen burner Use to protect our eyes to transfer a small amount of liquid to store liquid to heat substances to stir liquid 2. The correct order of lighting a Bunsen burner is: D B A C E EXPERIMENT Measuring length 1. Object Instrument Length 1. Length of the bench metre rule / half-metre rule / measuring tape 2. Length of your science textbook half-metre rule / plastic ruler 3. Diameter of a 50-cent coin plastic ruler 4. Circumference of a football measuring tape Answers vary with students. The appropriate unit is: 1. m 2. cm 3. cm 4. cm 2. How would you measure the thickness of a page of your science textbook using a plastic ruler? (a) Method: Measure the thickness of the book. Then divide it by the number of pages of the book. (b) The thickness of a page of the book: Thickness of a page = thickness of the book number of pages of the book = Answers vary with students. The appropriate unit is mm.

11 Unit 1 Introducing Science 11 EXPERIMENT Measuring volume Part A Measuring the volume of an object with regular shape 1. Measure and record the height, width and length of your science textbook. height = cm width = cm length = cm 2. Calculate the volume of the book. Volume of the book = = cm 3 Part B Measuring the volume of liquids 2. Record the volume of each container (V 1 ) as printed on the label in the table below. Container Volume on the label, V 1 (cm 3 ) Volume measured, V 2 (cm 3 ) A B (Answers vary with students.) C 4. Based on your results, is there any difference between V 1 and V 2? If yes, how would you explain the difference? The water splashed out of the container while being poured. (Accept other reasonable answers) Part C Measuring the volume of an object with irregular shape 1. Pour water into a measuring cylinder to half full. Take the reading. Let this volume be V 1. V 1 = cm 3 (Answers vary with students.) 2. Tie a thread to an object with irregular shape, e.g. a piece of plasticine. Lower the plasticine into the water. Read the new volume. Let this volume be V 2. V 2 = cm 3 (Answers vary with students.) 3. Calculate the volume of the piece of plasticine. Volume of the plasticine = V 2 V 1 = cm 3

12 12 Unit 1 Introducing Science EXPERIMENT Measuring temperature 3. Measure the temperature of hot water, tap water and iced water. Record the readings in the table below. Air in the room Hand Hot water Tap water Iced water Temperature ( C) (Answers vary with students.) EXPERIMENT Measuring mass 1. Item 1. A boy 2. A bag of oranges 3. A can of coke 4. A ten-dollar coin Instrument bathroom scale spring balance / electronic balance electronic balance electronic balance Mass Answers vary with students. The appropriate unit is: 1. kg 2. g 3. g 4. g 2. How would you measure the mass of 100 cm 3 of water using a measuring cylinder and an electronic balance? (a) Measure the mass of a dry (wet / dry) measuring cylinder (M 1 ) using an electronic balance. Then add 100 cm 3 of water to the measuring cylinder and measure the total mass (M 2 ). The mass of 100 cm 3 of water is equal to M 2 M 1. (b) The mass of 100 cm 3 of water: Mass of 100 cm 3 of water = M 2 M 1 The appropriate unit of the mass of 100 cm 3 of water is g.

13 Unit 1 Introducing Science 13 T hin king 1-59 Which stopwatch in Fig is more precise? Why? The mechanical stopwatch can measure time intervals accurate to 0.2 s. The digital stopwatch can measure time intervals accurate to 0.01s. The digital stopwatch is more precise than the mechanical stopwatch. EXPERIMENT Measuring the pulse rate Part A Measuring pulse rate with a stopwatch 1. Write down his / her resting pulse rate as Reading 1 in the table below. Reading 1 Reading 2 Reading 3 Resting pulse rate (pulses per minute) (Answers vary with students.) 4. Repeat Step 3 twice to obtain two more readings. 5. Calculate the mean resting pulse rate of your classmate in number of pulses per minute. His / her mean resting pulse rate is pulses per minute. (Answers vary with students.) Part B Measuring pulse rate with a data-logger with pulse rate sensor 4. Take the reading for two minutes. His / Her resting pulse rate is. Discussion What is the advantage of using a data-logger to measure pulse rate over the use of a stopwatch? The data-logger enables accurate and continuous pulse rate monitoring. (Answers vary with students.)

14 14 Unit 1 Introducing Science TEST YOURSELF Measurement Instrument(s) Unit(s) commonly used Unit symbol(s) 1. Length plastic ruler metre rule half-metre rule measuring tape kilometre km metre m centimetre cm millimetre mm 2. Volume ruler measuring cylinder cubic metre m 3 cubic centimetre cm 3 litre L millilitre ml 3. Temperature thermometer degrees Celsius C 4. Mass balance kilogram kg gram g 5. Time clock watch stopwatch hour h minute min second s

15 Unit 1 Introducing Science 15 REVISION EXERCISE 1-70 A. Multiple-choice Questions 1. B 4. C 2. A 5. D 3. C 6. D B. Short-answer Questions 7. (a) Fill in the boxes below to show the three components of the fire triangle. oxygen fuel heat (b) Which component of the fire triangle has been removed when we use a sand bucket to put out a fire? Circle it in the above diagram. 8. (a) Which of them is a fair test? Experiment C (A / B / C) is a fair test. (b) Which variables should be kept constant in the experiment? Put a in the appropriate boxes. The size of the parachutes The height from which the parachutes are dropped (c) What conclusion can Tim obtain from the fair test? The shape of the parachutes The time the parachutes take to fall A bigger parachute falls more slowly (faster / more slowly) than a smaller parachute.