Name Date: Effects of Heat and Heat Transfer (Test) Section A: MCQ [5 marks] 1, The diagram below shows a copper box filled with boiling water. The outside surface of each side is different. dull white dull black J shiny black shiny white From which side will the most heat escape by radiation? A. dull black B. dull white C. shiny black D. shiny white 2. A beaker of water is heated at the bottom to form a convection current in the water. An explanation of the convection current contains four statements. 1 The water at the bottom becomes warmer The density of the water decreases are Less dense water rises and cold water moves in to replace it. * Water expands What is the correct order of these statements? A. 1929394 B. 1933492 C. 1949293 D. 1949332 503. The diagram shows liquid in a saucepan being heated on an electric cooker. — * (___—- saucepan liquid a I metal plate of cooker Be z—_] heater ‘What best describes the type of energy transfer taking place at X, Y and Z? x Y Zz A ‘conduction| convection radiation B. convection conduction radiation c convection radiation conduction D. radiation conduction convection 4. \gram shows part of a refrigerator. ‘cooling fins. at back of reftigerator ‘The cooling fins are painted black because black surfaces are A. good absorbers of heat B. poor absorbers of heat C. good emitters of heat D. . poor emitters of heat 5. The diagrams show a model of an automatic fire alarm,_bimetallic strip fire alarm x LLL Which statement is true? A. Metal X does not expand when heated. B. Metal X is a poor conductor of heat. C. Electric current flows faster in metal Y. D. Metal Y expands more than metal X. Section B: Short Answer Questions [10 marks] 1, A student has to construct a thermostat for a refrigerator as shown in fig BI for his science project. He was asked to choose from five different metals A, B, C, D and E to form the bimetallic strip. The rate of expansion of the five metals are shown in table B2 with 4 being the metal that expands the most and 1 being the metal that expands the least. cooling unit metal X electrical outside refrigerator wirings = LI metal ¥ bimetallic strip [ ee FigBL1 energy source Metal Rates of expansion A 2 B 1 € 3 D 4 E 3 Table B12 (2) @) State whether the refrigerator in fig B1 is at a ‘warm state’ or ‘cold state’. [1] 52Gi) Deseribe what happens to the bimetallic strip as the refrigerator warms up. [2] (b) Suggest two metals from table B1.2 that the student can use as metal X and metal Y to make the thermostat most responsive. Explain your answer. [2] Metal X: Metal Y: Explanation: Fig B2.1 below shows the cross-section of the Magic pot, sold by household products company, which is claimed that it will continuously slow cook your food from the residual heat for the next four to six hours after removing the heat source. e, Outer Cover Inner Pot Cover (insulation Structure Inner Pot (Aluminum and Stainless Stee!) 53Different parts of the Magic pot are made up of different materials that affect heat transfer through conduction, convection and radiation. The inner pot cover is made up of tempered glass, (a) How does tempered glass prevent heat loss? [1] The inner pot is made up of aluminium and stainless ste (b) State why metals like aluminium and stainless steel causes the inner pot to gain heat quickly. Explain your answer. [2] (©) State how the shiny surfaces of aluminium and stainless steel causes the inner pot to gain heat quickly. Explain your answer. [2] 54Section C: Free Response Questions [10 marks] 1. (a) Ali wants to investigate heat transfer in the laboratory. He filled an electric kettle with ‘water as shown in figure C1 heating element Fig C1 (i) Explain why the heating element is positioned near the bottom. [2] (ii) Figure C2 shows a temperature-time graph of water being heated in the kettle when the heating element is positioned at the bottom as shown in figure C2. (On figure C2, draw another graph showing the change of temperature with time when the heating element is positioned at the top of the water. [1] Temperature 4 Time Fig C2 55(b) The hot water is then transferred to two metal cans as shown below after one period. Both cans are placed the same distance from an electric heater. The initial temperature of the water in each can is the same. electric heater ul ‘lack surtace i] 7 cnx Fig C3 _> Biver surface (i) Name the main process by which energy from the electric heater reaches the cans. [1] (ii) The temperature of the water in both cans rises. In which can, X or Y, will the temperature rise more quickly? Explain your answer. [2] (iii) Ifthe lids are not placed on the cans, the mass of water in each can decreases even before the water reaches the boiling point, Explain what happens to the water to cause this decrease in mass. [1] 56(©) Ali then decided to use a vacuum flask, as shown in Fig C4 for his grandma’s daily use as it is capable of keeping hot water for a long time without continuous heating. room temperature= 30°C plastic stopper 90°C glass liquid walls silvered on the inside surface | (i) Explain how the silvered wall help to keep the hot water hot for a long time. [1] (ii) Explain how the vacuum between glass walls help to keep the hot water for a Jong time, [2] 37