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Question 1
A student is adding ice to their drink to cool it down. |
a) | The student adds 3 ice cubes each of mass 2.7 g to their drink at 12°C. The mass of the drink is 300 g. The ice cubes were initially at a temperature of -5°C. Calculate the final temperature of the drink. You may assume no energy is lost to the surroundings.
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b) | Define specific latent heat of fusion.
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c) | The student claims their drink would cool down more if they used the same mass of ice but with a larger surface area. Explain why the student is incorrect.
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Question 2
This question is about the internal energy of a system. |
a) | State what is meant by the internal energy of a system.
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b) | A solid sample of a substance is placed in a sealed container and heated at a constant rate. The graph below shows how the temperature of the sample varies with time. Describe the solid phase section of the graph in terms of the arrangement and motion of the particles in the substance.
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c) | Explain why there is no change in temperature from B to C.
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d) | The mass of the sample is 225 g. The power of the heater was 1,000 W. The change in state from B to C took 2 minutes. Calculate the specific latent heat of fusion of the sample.
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Question 3
A 2.5 kW kettle is filled with 200 g of water at 5°C. The kettle is turned on for 3.5 minutes. |
a) | Calculate the energy required to raise the temperature of the water to its boiling point.
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b) | The specific latent heat of vaporisation of water is 2,268,000 J kg-1. Calculate the mass of steam produced when the kettle is on for 3.5 minutes.
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c) | The student records the mass of the water remaining at 3.5 minutes. Give one reason why the mass of water remaining is higher than the expected value.
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Question 4
A glassmaker moulds glass by heating it in a furnace and crafting its shape while it is malleable. |
a) | The specific heat capacity of glass is 753 J kg °C-1. Calculate the energy required to raise the temperature of 120 g of glass from 22°C to 600°C.
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b) | The glassmaker cools the glass by placing it in a bucket of water. The mass of water in the bucket is 3.5 kg at a temperature of 22°C. The temperature of the glass is 480°C when it is placed into the water. Calculate the final temperature of the water and the glass.
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Question 5
A student takes an ice cube out of the freezer. When she takes the ice cube out of the freezer its temperature is -17 °C. She heats the ice cube until it melts, and the water produced boils. |
a) | Sketch a graph to show how the temperature changes with time. Assume the rate of energy transfer to the ice is constant.
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b) | Calculate the energy transferred to the 20 g of water as it is heated from its melting point to its boiling point. The specific heat capacity of water is 4,200 J/kg°C.
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It took 42 s for the heater to heat the water from 0 °C to 100 °C. Calculate the power of the heater.
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c) | Describe the changes in arrangement and movement of the particles as the ice melts.
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Question 6
A student is investigating the specific heat capacity of a metal block. |
a) | Describe how the student could find the specific heat capacity of the metal block.
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b) | The student uses a 12 V heater with a current of 3 A. Calculate the energy transferred to the metal block in 10 minutes.
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The student used a metal block with a mass of 1 kg. The temperature change during the experiment was 16.2°C. |
c) | Calculate the specific heat capacity of the metal block and hence determine the material it is likely to be made from.
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Question 7
Sam wants to keep his tea hot by using a USB heater under his mug. |
a) | Calculate the energy transferred to the mug by the heater in 15 minutes.
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b) | The mug loses 4 kJ of heat to the surroundings while the mug is on the heater. Calculate how much energy is used to heat the tea.
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c) | Calculate the final temperature of the tea after 15 minutes.
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d) | How could the student reduce the heat lost to the surroundings?
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Question 8
Mary is setting up a new hot tub. When fully filled and heated it contains 1,000 litres of water at 38°C. The hot tub heater is rated at 3 kW. Mary fills the hot tub with a hose pipe with water at 5°C. Once filled, she switches the heater on. |
a) | Calculate the energy transferred to the water as it is heated from 5°C to 38°C. The specific heat capacity of water is 4200 J/kg°C. 1 litre of water = 1 kg.
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b) | Calculate how long it would take for the 3 kW heater to heat the water from 5°C to 38°C. Give your answer to the nearest hour.
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c) | Mary found it took 15.5 hours for the hot tub to reach 38°C. Suggest why the time recorded is much higher than the calculated value.
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d) | Suggest two ways Mary might reduce the time it takes to heat the hot tub without using a different hose.
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Question 9
The sun can be used to heat water inside solar heating elements. The sun transfers 1,370 J per second per square metre on the Earth's surface. |
a) | Each solar heating element is 1.2 m long and 90 cm wide. Calculate the area of the solar heating element.
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b) | A homeowner has 4 of these panel installed on their roof. Calculate the energy incident per second on the solar panel array.
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c) | The array of panels contains 240 kg of water combined. Calculate the temperature change of the water when exposed to the sun for 2 hours.
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Question 10
A student is investigating the properties of stearic acid. The stearic acid is heated in a boiling tube in a water bath to 90 °C. The student removes the boiling tube from the water bath, records the temperature and starts a timer. The temperature is recorded every 10 s for 150 s. |
a) | Plot a graph of time against temperature for the student's results.
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b) | The graph plotted is a line graph. Explain why a line graph more appropriate than a bar chart for temperature data.
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c) | Using the graph, identify the freezing point of stearic acid.
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d) | Describe what happens to the arrangement and motion of the particles within the acid as it freezes.
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e) | The mass of stearic acid used was 50 g and the specific heat capacity of stearic acid is 2,300 J/kg°C. Calculate the energy transferred between 0 s and 30 s.
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Question 11
A student is investigating the specific heat capacity of an unknown liquid. Their method is below:
c = m × ΔθQ |
a) | Using the data from the table, calculate the mass of the unknown liquid.
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b) | In step 4 of the student's method, the heater is turned off and the temperature recorded. Explain why is this incorrect.
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c) | The current through the circuit was 3 A. Calculate the energy transferred by the 12 V heater during the 10 minutes it was turned on.
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d) | During the experiment the student recorded an initial temperature of 22oC and a final temperature of 45oC. |
Calculate the temperature change and the hence determine the specific heat capacity of the unknown liquid.
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e) | State the name of the material the liquid is likely to be made from. Ethanol
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f) | Explain why the calculated value of specific heat capacity is different to the accepted value. You should refer to the student's method in your answer.
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Question 12
A piece of iron of mass 4.5 kg is heated in a furnace to 1,250°C before being plunged into a bath of cold water containing 20 kg of water at 5°C. The specific heat capacity of iron is 451 J kg-1 °C-1. |
a) | The iron will cool when placed in the water bath. Eventually the iron bar will be in thermal equilibrium with the water. Describe what is meant by thermal equilibrium.
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b) | The iron bar is heated from room temperature at 22°C up to 1,250°C. The specific heat capacity of iron is 451 J/kg°C. Calculate the amount of energy required to heat the iron bar.
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c) | When a larger piece of iron is placed in the water bath, some of the water boils. Describe what happens to the internal energy of the water as it boils.
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d) | Calculate the energy required to boil 3.5kg of water at 100 oC into steam at 100 oC. The specific latent heat of water is 2.23×106 J/kg.
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Question 13
a) | An ice cream is removed from the freezer at -17 °C and is left on the table at room temperature 22°C. State the equation linking energy transferred, mass, and latent heat.
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b) | The ice cream had a mass of 150 g and the specific latent heat is 336 kJ kg-1. Calculate the energy required to melt the ice cream.
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c) | The graph below shows how the temperature of the ice cream varies with time. |
c i) | Describe how the internal energy of the ice cream varies with time between 0 s and 80 s.
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