time for the ice cube to melt totally is measured. The 4 trays are made of aluminium, copper, wood and steel. tray

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1 NAME : F.3B ( ) Marks: /50 Form Three Physics Test on Heat transfer Time allowed: 50 minutes Section A (30 marks) 1. The figure shows an experiment. One ice cube is placed on each of the 4 trays and the Ice cube time for the ice cube to melt totally is measured. The 4 trays are made of aluminium, copper, wood and steel. tray (a) What is the purpose of the experiment? (1 mark) (b) State TWO precautions so that the experiment makes a fair comparison. (c) Which do you expect to have shortest time for melting the ice cube totally? Explain your choice. (d) The idea is applied in defrosting plate as shown in the figure below. Frozen meat is placed on the plate which speeds up the defrosting. (i) Describe and explain one feature of the plate for speeding up the defrosting. (ii) Suggest one treatment on the plate before using which can further speed up the defrosting. (1 mark) 2. The picture shows a cooler to take cold drinks out. (a) State and explain TWO features of it which helps to keep cold drinks cool for longer. (4 marks) (b) What colour(s) will you select for the outside of the cooler? Explain your answers briefly.

2 (c) Ice cubes are added to keep the temperature lower. Explain with aid of diagram where one should put the ice cubes in a bag which is inserted to the bottom or leave the ice cubes floating on the top of the water inside the cooler. (4 marks) 3. The picture shows a baked ice-cream cake. Ice cream is slightly melted and used to fill a hollow sponge cake. Then, the cake is covered with a mixture of egg white and cream and then baked. When served, the ice cream has hardly melted while the egg white layer is very hot. (a) Explain with TWO reasons why the ice-cream does not melt during the baking. (b) The use of sponge cake helps to prevent the ice cream from melting fast. Explain. 4. In a competition, participants need to transfer a large block of ice along a long path. The winner is the one who can manage to arrive at the largest size of ice block. (a) Suggest and explain THREE methods individually based on conduction, convection and radiation. (6 marks)

3 (b) It is stated that a large block of ice will melt slower than smaller pieces of ice blocks of the same total mass. Do you agree? Why? Section B (20 marks) Write your answers in the spaces provided below The above figure shows the aluminium heat sink of an audio amplifier which is used to transfer heat away from the components inside the amplifier. Which of the following statements about the heat sink is / are correct? (1) The heat sink is made of aluminium so that it can transfer heat away faster by conduction. (2) The heat sink is silver in colour so that it can transfer heat away faster by radiation. (3) The heat sinker has a fin-like design to increase the surface area so that it can transfer heat away faster by conduction to air. A. (2) only B. (3) only C. (1) and (2) only D. (1) and (3) only aluminium heat sink 2. Comparing plastic and air, which is a better heat conductor and why? A. Plastic is a better heat conductor because it conducts better. B. Plastic is a better heat conductor because its molecules are more closely packed. C. Air is a better heat conductor because it has a higher specific heat capacity. D. Both plastic and air are poor heat conductor and they cannot be compared. 3. Eskimos stay in igloos (ice-house) because (1) ice is good insulator of heat (2) white ice is a good absorber of heat (3) white ice is a bad radiator of heat. B. (1) and (3) only

4 4. Which of the following colours is the most suitable for containing hot and cold drinks? Hot drinks Cold drinks A. white cup white cup B. white cup black cup C. black cup black cup D. black cup white cup 5. We usually weak light-coloured clothes in summer because A. light-coloured objects are good emitters B. light-coloured objects are bad emitters C. light-coloured objects are good absorbers D. light-coloured objects are bad absorbers. 6. Which of the following statements about conduction is/are correct? (1) Conduction transfer heat from hot places to cold places at any time. (2) Conduction cannot occur in air. (3) All liquids are poor conductors. B. (1) and (2) only 7. The figure shows a vacuum flask with two glass walls. Which of the following statements are correct? (1) The surface P and Q are painted silvery to reduce heat loss. (2) The cork stopper reduces heat loss by conduction and convection. (3) The vacuum between the double glass walls reduces heat loss by radiation. A. (1) and (2) only B. (1) and (3) only surface P surface Q cork stopper hot liquid glass walls vacuum

5 8. The Sun transfers heat to Earth by (1) conduction (2) convection (3) radiation A. (2) only B. (3) only C. (1) and (3) only 9. We use aluminium foil to cover sweet potatoes when having barbeques. (1) Aluminium foil acts as good absorber. (2) Aluminium foil is a good conductor. (3) Aluminium foil acts as bad radiator.. B. (2) only C. (1) and (2) only D. (2) and (3) only 10. Which of the following statements is/are true for convection? (1) It transfers heat from hot places to cold places. (2) It occurs in fluids but not in solids. (3) It transfers heat in all directions. B. (1) only C. (2) only D. (1) and (2) only E. (2) and (3) only End of Test