Specific latent heat (E = m L)

Question 1

904 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 2

How much energy is needed to boil away 1.5 kg of water at 100 °C, in kJ? (Specific latent heat of vaporisation of water = 2260 kJ/kg)

Answer kJ

Question 3

Why does steam at 100 °C cause worse burns than water at 100 °C?

• A. Steam is denser
• B. Steam is hotter than 100 °C always
• C. Water does not transfer heat
• D. Steam releases its large latent heat as it condenses on the skin

Question 4

80 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 5

How much energy is needed to boil away 0.1 kg of water at 100 °C, in kJ? (Specific latent heat of vaporisation of water = 2260 kJ/kg)

Answer kJ

Question 6

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

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

Question 7

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 8

How much energy is needed to boil away 0.25 kg of water at 100 °C, in kJ? (Specific latent heat of vaporisation of water = 2260 kJ/kg)

Answer kJ

Question 9

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

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

Question 10

246 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 11

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 12

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

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

Question 13

246 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

How much energy is needed to melt 0.1 kg of ice at 0 °C, in kJ? (Specific latent heat of fusion of water = 334 kJ/kg)

Answer kJ

Question 15

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

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

Question 16

160 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