Specific latent heat (E = m L)

Question 1

1808 kJ of energy melts or boils 0.8 kg of a substance with no change in temperature. What is its specific latent heat, in kJ/kg?

Answer kJ/kg

Question 2

On a heating curve for ice, why does the temperature stay at 0 °C for a while?

• A. Energy is breaking bonds between particles to melt the ice, not raising their kinetic energy
• B. Energy is destroyed while melting
• C. The heater has turned off
• D. Ice cannot be heated

Question 3

How much energy is needed to melt 0.5 kg of ice at 0 °C, in kJ? (Specific latent heat of fusion of water = 334 kJ/kg)

Answer kJ

Question 4

167 kJ of energy melts or boils 0.5 kg of a substance with no change in temperature. What is its specific latent heat, in kJ/kg?

Answer kJ/kg

Question 5

Why is the latent heat of vaporisation of water much larger than its latent heat of fusion?

• A. Water vapour has no particles
• B. Melting needs more energy
• C. Boiling happens at a lower temperature
• D. Boiling separates particles completely; melting only loosens them

Question 6

How much energy is needed to boil away 0.5 kg of water at 100 °C, in kJ? (Specific latent heat of vaporisation of water = 2260 kJ/kg)

Answer kJ

Question 7

133.6 kJ of energy melts or boils 0.4 kg of a substance with no change in temperature. What is its specific latent heat, in kJ/kg?

Answer kJ/kg

Question 8

On a heating curve for ice, why does the temperature stay at 0 °C for a while?

• A. Ice cannot be heated
• B. Energy is breaking bonds between particles to melt the ice, not raising their kinetic energy
• C. The heater has turned off
• D. Energy is destroyed while melting

Question 9

How much energy is needed to boil away 0.2 kg of water at 100 °C, in kJ? (Specific latent heat of vaporisation of water = 2260 kJ/kg)

Answer kJ

Question 10

41 kJ of energy melts or boils 0.2 kg of a substance with no change in temperature. What is its specific latent heat, in kJ/kg?

Answer kJ/kg

Question 11

Why is the latent heat of vaporisation of water much larger than its latent heat of fusion?

• A. Water vapour has no particles
• B. Boiling separates particles completely; melting only loosens them
• C. Boiling happens at a lower temperature
• D. Melting needs more energy

Question 12

How much energy is needed to boil away 0.5 kg of water at 100 °C, in kJ? (Specific latent heat of vaporisation of water = 2260 kJ/kg)

Answer kJ

Question 13

400.8 kJ of energy melts or boils 1.2 kg of a substance with no change in temperature. What is its specific latent heat, in kJ/kg?

Answer kJ/kg

Question 14

Why does sweating cool you down, in terms of latent heat?

• A. Evaporating sweat takes the latent heat it needs from your skin
• B. Sweat reflects sunlight
• C. Sweat releases latent heat into the skin
• D. Sweat is colder than blood

Question 15

How much energy is needed to melt 0.2 kg of ice at 0 °C, in kJ? (Specific latent heat of fusion of water = 334 kJ/kg)

Answer kJ

Question 16

1808 kJ of energy melts or boils 0.8 kg of a substance with no change in temperature. What is its specific latent heat, in kJ/kg?

Answer kJ/kg