AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Exam Practice: Specific latent heat
Specific latent heat · Particle model of matter · Lesson 4 of 6 · 14 marks · 15 minutes
|
Name |
|
Date |
|
Instructions
• Answer all the questions.
• Write your answers in the spaces provided.
• The marks for each question are shown in brackets - use this as a guide to how much to write.
• The answers are on separate pages at the back. Attempt every question before you look at them.
• Answer all questions. Use the mark allocation as a guide to how much to write.
Question 1 CALCULATE (2 marks)
Calculate the energy needed to melt 0.35 kg of ice at 0 °C. The specific latent heat of fusion of water is 334 000 J/kg. Use the equation: energy for a change of state = mass × specific latent heat
|
|
|
|
|
|
(Total for Question 1 = 2 marks)
Question 2 USE THE GRAPH (4 marks)
The graph shows how the temperature of a solid changes as it is heated at a steady rate until it is a gas. (a) State the melting point. (b) What is happening between 2 and 8 minutes? (c) Explain why the temperature stays constant during this time.
|
|
|
|
|
|
|
|
|
|
|
|
(Total for Question 2 = 4 marks)
Question 3 DISTINGUISH (2 marks)
Describe the difference between specific heat capacity and specific latent heat.
|
|
|
|
|
|
(Total for Question 3 = 2 marks)
Question 4 CALCULATE (3 marks)
Calculate the energy needed to change 0.50 kg of water at 100 °C into steam. The specific latent heat of vaporisation of water is 2 260 000 J/kg.
|
|
|
|
|
|
|
|
(Total for Question 4 = 3 marks)
Question 5 EXPLAIN (3 marks)
Steam at 100 °C causes a more serious burn than boiling water at 100 °C. Explain why.
|
|
|
|
|
|
|
|
(Total for Question 5 = 3 marks)
TOTAL FOR PAPER = 14 MARKS
|
|
Answers and mark scheme
Check your answer only once you have written one.
Question 1 (2 marks)
0.35 × 334 000 = 116 900 J
• Correct substitution 1 mark
• 116 900 J 1 mark
Question 2 (4 marks)
(a) 0 °C. (b) The solid is melting (changing state to liquid). (c) The energy supplied changes the potential energy of the particles (breaking bonds), not their kinetic energy, so the temperature does not rise.
• 0 °C 1 mark
• Melting 1 mark
• Energy used to break bonds or change potential energy 1 mark
• Kinetic energy or temperature does not increase 1 mark
Question 3 (2 marks)
Specific heat capacity is the energy needed to raise the temperature of 1 kg by 1 °C. Specific latent heat is the energy needed to change the state of 1 kg with no change in temperature.
• Specific heat capacity: temperature change 1 mark
• Specific latent heat: change of state, no temperature change 1 mark
Question 4 (3 marks)
0.50 × 2 260 000 = 1 130 000 J
• Correct substitution 1 mark
• 1 130 000 J 1 mark
• Unit J 1 mark
Question 5 (3 marks)
When steam condenses it releases a large amount of energy (latent heat) to the skin, in addition to the energy released as the water cools, so more energy is transferred to the skin.
• Steam condenses on the skin 1 mark
• Releases latent heat 1 mark
• So more energy is transferred than from the water alone 1 mark