Chapter 1.3 - 'Latent Heat'

Question 1

Define ‘Latent Heat’.

Answer 1

The energy released or absorbed during a change of state.

Question 2

State how a substances temperature change whilst changing form?

Answer 2

It remains constant.
or
Does not change.

Question 3

State how Latent Heat is calculated.

Answer 3

Q = mL

Q is the heat energy transferred in joules (J)
m is the mass in kilograms (Kg)
L is the latent heat in joule per kilogram (J/kg)

Question 4

Explain how ‘evaporation’ works.

Answer 4

Molecules with higher KE are pushed to the surface, these molecules carry higher momentum and therefore are more likely to escape from the surrounding body. This process continues until the substance is gone.

Question 5

State what the rate of evaporation depends on.

5 points

Answer 5

1. Volatility - More-volatile liquids evaporate faster
2. Surface Area - Greater evaporation occurs where more area is exposed to air.
3. Temperature - Liquids with more energy evaporate faster.
4. Humidity - Less evaporation occurs in humid environments.
5. Air movement - More air movement e.g wind the higher evaporation.

Question 6

Regarding the movement of particles, why do solids melt?

Answer 6

As a substance gets heats, the bonds between the molecules move further and further apart, weakening the structures stability

Question 7

Explain why the temperature doesnt increase whilst changing heat.

Answer 7

All the heat energy is increasing the potential energy of the molecules rather than the kinetic energy.

This reduces the inter-particle or intermolecular forces.

Question 8

State what L represents.

State the unit.

Answer 8

Latent Heat

J/Kg