Matter - 2 - Evaporation and Boiling

What is latent heat?

• Heat causing a temperature rise

• Heat used in changing state without temperature change

• Heat used to increase pressure

• Heat lost during condensation

Which of the following correctly defines specific latent heat?

• Heat absorbed per mole of substance

• Heat absorbed per unit temperature change

• Heat absorbed/released per unit mass during a state change

• Heat stored in solid state

The SI unit of specific latent heat is:

• J

• J/m²

• J/kg

• cal/kg

When a solid changes into a liquid, the heat involved is called:

• Latent heat of vaporization

• Latent heat of condensation

• Latent heat of fusion

• Specific heat capacity

What is the specific latent heat of fusion of ice?

• 2260 × 10³ J/kg

• 336 × 10³ J/kg

• 100 × 10³ J/kg

• 540 cal/g

During the melting of ice at 0°C, the temperature of the system:

• Increases gradually

• Decreases slowly

• Remains constant

• Increases and then decreases

Which of the following statements is true about the change of state?

• Temperature increases during melting

• It is a chemical change

• It is irreversible

• It is a physical and reversible change

Heat required to change the state of 0.5 kg ice to water at 0°C is:

• 168 × 10³ J

• 113 × 10³ J

• 336 × 10³ J

• 226 × 10³ J

Evaporation occurs at:

• Only at boiling point

• Only above boiling point

• At all temperatures below boiling point

• Only at 0°C

Why does evaporation cause cooling?

• Because particles lose energy

• Because only cold particles evaporate

• Because fast-moving particles escape, lowering average kinetic energy

• Because it creates bubbles