Year 11 Physics Heat Practice Test.pdf

Question 1 The diagram below shows the effect of solar heating on the movement of air. (a) State the term used to describe the process of heat transfer illustrated in the diagram. (1 mark) (b) D...

Question 1 The diagram below shows the effect of solar heating on the movement of air. (a) State the term used to describe the process of heat transfer illustrated in the diagram. (1 mark) (b) Describe the process of heat transfer shown in the diagram. (2 marks) (c) The specific heat capacities of two different materials are identified below. Material 𝑐 (J/kg ºC) Concrete 880 Grass 800 3.6 x 106 J of heat is transferred from the sun per m2 per hour. (1) State and explain which material has the greatest increase in temperature when 3.6 x 106 J of heat is transferred. (2 marks) (2) The initial temperature of the concrete was 5ºC. Calculate the final temperature of 1 m2 of concrete (𝑚 = 240 kg) after 2 hours. (4 marks) Question 2 The diagram below shows the components of a refrigerator. (a) A gas named R–134a is pressurised inside the compressor which increases its temperature. State whether the thermal energy of R–134a increases or decreases when the gas is pressurised and give a reason. (2 marks) (b) The pressurised gas is forced into the coils of the condenser on the outside of the refrigerator. Heat is transferred from the pressurised R–134a to the outside air by conduction. Describe the process of heat transfer by conduction. (2 marks) (c) The phase of R–134a changes from gas to liquid as heat is transferred to the outside air. (1) State the term used to describe the transition from gas to liquid. (1 mark) (2) Describe changes in the motion of R–134a molecules when heat is transferred to the outside air. (2 marks) (d) The liquid enters the evaporator where it is vaporised. The latent heat used to vaporise the liquid is transferred from inside the refrigerator. (1) Define the latent heat of vaporisation. (1 mark) (2) Calculate the quantity of latent heat required to change the phase of 0.8 kg of R–134a if the latent heat of vaporisation is 2.17 x 105 J/kg. (2 marks) (3) Explain why the temperature of the R–134a is constant when latent heat is transferred. (2 marks) (e) R–134a has a boiling point of 246.85 K. (1) Convert this temperature to ºC. (2 marks) (2) Describe changes in the arrangement of R–134a molecules when the material transitions from liquid to gas. (2 marks) (f) R–134a expands when heated inside the evaporator. The coefficient of volume expansion of R–134a is 3.24 x 10–3 °C–1. Calculate the increase in volume of 120 mL of R–134a when the temperature increases by 20ºC. (2 marks) Question 3 Giraffes have adaptations that help them survive in the desert. Beneath the spots on a giraffe’s body are networks of blood vessels that bring warm blood to the skin (a) Heat is transferred from blood to skin by thermal radiation. Describe how the emission of thermal radiation lowers blood temperature. (2 marks) (b) The giraffe has evolved a sophisticated method of cooling its brain. Air flowing into its nose causes water to evaporate and cool blood beneath the skin. (1) Describe and explain how evaporation reduces the temperature of blood beneath the skin. (2 marks) (2) Cooler blood travels from the nose to the carotid rete. Cooler blood entering the carotid rete passes by warmer blood travelling in the carotid artery to the brain. Describe how this process prevents a giraffe from overheating. (2 marks) Question 4 Bridges are constructed with expansion joints such as the one shown below. (a) Describe and explain the function of expansion joints on a bridge. (2 marks) (b) The bridge is made in two halves. Each half is made of steel (𝛼 = 12 x 10-6 ºC–1) and is 10 m long at 18°C. Calculate the minimum distance (d) between the two halves at 18°C so that no damage occurs when the temperature increases to 45°C on a hot day. (3 marks) (c) Convert 45°C to units of °F. (2 marks) Question 5 An experiment was performed to measure the temperature of a Bunsen burner flame. A lump of copper of mass 0.12 kg is heated in the flame for several minutes. The copper is then transferred quickly to a beaker, of negligible heat capacity, containing 0.45 kg of water, and the temperature rise of the water measured. Specific heat capacity of water = 4180 J/kg ºC Specific heat capacity of copper = 390 J/kg ºC The temperature of the water increases from 15ºC to 35ºC. (a) Calculate the quantity of heat transferred to the water. (2 marks) (b) The copper and the flame are in thermal equilibrium after several minutes. State what is meant by thermal equilibrium. (1 mark) (c) The temperature reached by the copper in the flame is calculated using the equation below. (𝑇#$ x (𝑚% 𝑐% + 𝑚!" 𝑐!" )) − 𝑚% 𝑐% 𝑇% 𝑇!" = 𝑚!" 𝑐!" Calculate the temperature reached by the copper in the flame. Assume no heat is lost when the copper is transferred. (2 marks) (d) When the lump of copper entered the water, some of the water was turned to steam. The latent heat of vaporisation of steam is 2.25 x 106 J/kg. (1) State the other piece of data needed to calculate the energy used to produce this steam. (1 mark) (2) Without further calculation, describe how this further measurement could be made. (2 marks)