Chapter 12: Scientific Experiments | Education PDF

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Twelve Scientific experiments Introduction...

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Twelve Scientific experiments Introduction LY In Standard Four, you learnt about the procedures for conducting a scientific experiment and you measured water temperature. Furthermore, in chapter six of this book, you learnt about light and conducted N experiments to examine light rays as they pass through convex and O concave lenses. You also performed an experiment and observed how a light ray bends as it encounters a lens. In this chapter, you will learn and perform experiments on the expansion and contraction of solid, SE liquid and gaseous materials.You will also perform experiments on how heat travels through solid, liquid and gaseous materials, how to prevent heat loss and the determination of body temperature in humans. U Experiment 1: Expansion and contraction of solid materials E Aim: To observe the expansion and contraction of a metal ball N when it is heated or cooled LI Materials: A metal ring, a metal/iron ball, a clamp, a stand, a source of heat (a Bunsen burner, a spirit lamp, a candle, a gas stove N or a kerosene stove) and a matchbox Procedure O 1. Take the metal ball and pass it through the metal ring when both the ball and the ring are at the same room temperature. R 2. Make sure the metal ball goes exactly through the ring of the metal ring as shown in Figure 1(a). FO 3. Remove the ball from the ring and heat. See Figure 1(b). 4. Take the ball and pass it through the ring again. See Figure 1(c). What do you see? 183 SCIENCE AND TECHNOLOGY STD V.indd 183 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE 5. Let the ball cool for some time. 6. Try to pass the ball again through the ring of the metal ring. 7. Did the metal ring pass through the ring? LY N (a) (b) O SE (c) (d) U E Figure 1: Experiment on the expansion and contraction of a metal ball N Results LI When the metal ball was heated, it did not pass through the metal ring because it expanded and increased in size. After cooling, the metal N ball was able to pass through the metal ring because it contracted and decreased in size. O Conclusion R This experiment shows that, when a metal ball is heated, it expands FO and that, when it is cooled, it contracts. 184 SCIENCE AND TECHNOLOGY STD V.indd 184 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE Experiment 2: Expansion and contraction of liquids Aim: To observe the expansion of water when it is heated and the contraction of water when it is cooled. Materials: Coloured water, normal water, a one holed-bottle cork, a glass bottle, a glass tube, a pot, a water bath, a source of heat (like a Bunsen burner, a spirit lamp, a gas or kerosene stove), a matchbox and a coloured pen Procedure LY 1. Fill the glass bottle with coloured water. 2. Place the cork on the top of the glass bottle. 3. Insert the glass tube into the glass bottle through the hole of the N cork. 4. Mark on the level of water in the glass tube using the coloured pen. O 5. Place the bottle containing coloured water into a water bath containing normal water. See Figure 2. SE 6. Place the bottle into the pot containing normal water on the stove and heat. 7. Leave it for a moment. Has the level of coloured water in the tube changed? U 8. Remove the glass bottle from the pot and put it in the water bath and leave it to cool. 9. Observe what happens. What is the importance of using coloured E water in this experiment? N LI Glass tube N Bottle Hot water Pot O Stove R FO Coloured water Figure 2: Experiment on the expansion and contraction of water 185 SCIENCE AND TECHNOLOGY STD V.indd 185 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE Results When the water in the bottle was heated, its level in the glass tube rose (increased) and when it was cooled the level dropped (decreased). Conclusion In this experiment, you have observed that, when water is heated, it expands, and that, when it is cooled, it contracts. LY Experiment 3: Expansion and contraction of gases N Aim: To observe the expansion and contraction of air O Materials: Water, a pot, a balloon, a plastic bottle, a stove, a thread and a matchbox Procedure SE 1. Take the balloon and tie it on the top of the plastic bottle using a thread (see Figure 3(a)). 2. Pour the water into the pot, turn on the stove, put the pot on the U stove and heat the water. 3. Place the bottle tied with the balloon into the pot containing the hot water. See Figure 3(b). What do you see? E 4. Remove the bottle that is tied with the balloon from the hot water N and dip it into cold water. What do you see? LI N O R (a) FO (b) Figure 3: Experiment on the expansion and contraction of air 186 SCIENCE AND TECHNOLOGY STD V.indd 186 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE Results When the bottle tied with the balloon was placed in hot water, the volume of air in the balloon increased and caused the balloon to expand. When the bottle was placed in the cold water, the volume of air in the balloon decreased and caused the balloon to contract. Conclusion This experiment shows that, when air is heated, it expands, and that, LY when it is cooled, it contracts. N O Exercise 1 Answer the following questions. 1. SE Explain the meaning of the expansion and contraction of materials. U 2. Differentiate between the expansion of solids, liquids and gases. 3. Using a diagram, show the expansion and contraction of gases. E N Experiment 4: Heat transfer through solid materials LI Aim: To examine how heat is transferred through a piece of iron bar N Materials: A piece of iron bar, a piece of wood, wax, a source of heat (like a Bunsen burner, a spirit lamp, a candle, a gas or O kerosene stove), a matchbox and a wax or a candle Procedure R 1. Place the piece of iron bar on the piece of wood. See Figure 4(a). FO 2. Place the wax or candle on one edge of the piece of iron bar. See Figure 4(b). 187 SCIENCE AND TECHNOLOGY STD V.indd 187 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE 3. Place the source of heat at the other end of the piece of iron bar. See Figure 4(c). What happens to the wax or candle? Wax (a) (b) LY (c) N Figure 4: Heat transfer through a piece of iron bar O Results Heat travelled from the stove through the piece of iron bar, thus causing the wax or candle to melt. SE Conclusion U This experiment shows that heat is transferred between solid materials by conduction. E Experiment 5: Heat transfer through liquids N Aim: To observe how heat travels through water. LI Materials: A pot, water, small pieces of paper, a source of heat (like a N Bunsen burner, a spirit lamp, a gas or kerosene stove), a matchbox and a thermometer O Procedure 1. Take the pieces of paper and put them in the pot. R 2. Pour some water into the pot containing pieces of paper and leave FO it for five minutes, as shown in Figure 5(a). What did you see? 3. Measure the temperature of the water using the thermometer and record the readings. 188 SCIENCE AND TECHNOLOGY STD V.indd 188 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE 4. Put the pot containing the water and the pieces of paper on the stove, as shown in Figure 5(b). Wait for ten minutes. 5. Measure the temperature of the water using the thermometer and record the readings. 6. What happened to the pieces of paper and the temperature of the water in steps 4 and 5? LY N O SE U (a) (b) Figure 5: Heat transfer through water E Results N When the pieces of paper were put into the pot containing the water and LI left for five minutes, the pieces of paper remained at the bottom of the pot. This indicates that molecules of water are not free to move. When N the water in the pot was put on the stove and heated, the molecules of water gained heat energy and were free to move with the pieces of O paper. This process of heat transfer is called convection. Conclusion R This experiment shows that, when water is heated, it gains heat energy. FO Water molecules move more rapidly within a pot. This process is called heat transfer by convection. 189 SCIENCE AND TECHNOLOGY STD V.indd 189 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE Experiment 6: Heat transfer through air Aim: To observe the transfer of heat through air Materials: A piece of cloth, water, a rope or wire, pegs and a water basin Procedure 1. Pour the water into the basin. LY 2. Take the piece of dry cloth and put it in the water. What do you see? N 3. Remove the cloth from the water. Squeeze to remove the water and leave it in the sun for a period of about one hour. O 4. Then remove the cloth and examine it. What do you see? SE U E N LI Figure 6: Heat transfer through air N Results O When the dry cloth was put in the water, it became wet. When the wet cloth was squeezed and exposed to the sun, it was dried by the heat from the sun which was transferred through the air. R Conclusion FO This experiment shows that, when a cloth soaked in water is exposed to the sun, it is dried by the heat from the sun. The heat from the sun is transferred through air by a process known as radiation. 190 SCIENCE AND TECHNOLOGY STD V.indd 190 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE Experiment 7: Reducing heat loss Aim: To observe how a thermos flask prevents heat loss Materials: A thermos flask, a thermometer and hot water Procedure 1. Take the thermos flask and examine its external parts. What material are the external parts made of? 2. Remove the screw top/stopper. What materials is the screw top LY made of? 3. Remove the body (outer container of the thermos) slowly to get the inner chamber of the bottle. What is the colour of the surface of N the inner chamber of the thermos flask? O 4. Reassemble the thermos flask. 5. Pour some hot water into the thermos flask, measure the SE temperature and close the lid thoroughly. Wait for one hour and then measure the temperature of the water. What did you observe? U E N LI Figure 7(a): Thermos flask N Results O The outer part of the thermos flask is made of plastic or metal. The screw stopper or lid of the thermos flask is made of materials that are a poor conductor of heat, for example a piece of wood or plastic. The R inner chamber of the thermos flask has a glass wall that is coated with FO reflective silver and a vacuum has been left in the area between the inner and outer parts of the flask. The hot water in the thermos flask retained its temperature for more than one hour after the thermos flask lid had been closed (see Figure 7(b)). 191 SCIENCE AND TECHNOLOGY STD V.indd 191 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE Cap Silvered surface Sponge Hot water LY Plastic or metal jar N Vacuum O Rubber support SE Figure 7(b): Inner parts of a thermos flask Conclusion U This experiment shows that a thermos flask prevents heat loss. The walls of the outer part of a thermos flask are made up of glass so as to reduce heat loss by conduction. The surface of the wall of the inner E chamber of a thermos flask is covered with silver to reduce heat loss by radiation. The vacuum between the outer and inner walls of a thermos N flask prevents heat transfer by conduction and convection. LI N Experiment 8: Measuring body temperature O Aim: To measure body temperature Materials: A thermometer R Procedure FO 1. Take the thermometer and read its temperature by noting the number at the upper limit of the mark of the internal line of the thermometer. See Figure 8(a). 192 SCIENCE AND TECHNOLOGY STD V.indd 192 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE 2. Place the thermometer in the armpit so that it is in contact with the skin and wait for two minutes. See Figure 8(b). 3. Remove the thermometer from the armpit. Then read and record the temperature. See Figure 8(c). LY N O (a) (b) SE (c) Figure 8: Measuringt body temperature U Results When the thermometer was placed in the armpit, the internal line of the thermometer grew in length. E Conclusion N This experiment shows that, when the thermometer was put in the LI armpit, the internal line of the thermometer grew in length. This proves that heat transfer from the human body to a thermometer because of the N temperature of the human body is higher than the ambient temperature. O Exercise 2 R Answer the following questions. Section A: Fill in the blanks. FO 1. When tea boils, vapour travels by the process of __________. 2. When a person sits by a fire, he/she gets heat by the process of __________. 193 SCIENCE AND TECHNOLOGY STD V.indd 193 7/30/21 11:04 AM  FOR ONLINE USE ONLY DO NOT DUPLICATE 3. When you touch a piece of metal/iron in the morning and feel cold, heat is lost from your body by the process of _____________. 4. _________ is used to measure body temperature. Section B: Answer the following questions. 5. Explain how heat is transferred by conduction, convection and radiation. LY 6. Explain how a thermos flask prevents heat loss by conduction, convection and radiation. N O Vocabulary Balloon a small bag made of very thin rubber that expands Contraction SE when filled with air or gas the process of shrinking in size U Cork a substance used as a bottle stopper Expansion an act of increasing or making something increase in E size N Metal ball a sphere made of metal LI Metal ring a metal object with a round shape like a bangle Vacuum a space that is completely empty N O R FO 194 SCIENCE AND TECHNOLOGY STD V.indd 194 7/30/21 11:04 AM