Internal Energy and Energy Transfers

What is the internal energy of a substance

• The energy stored by the particles

• The sum of the total kinetic and potential energies that make up the system

How does heating affect the energy of a substance?

• Heating transfers energy to the substance

• It increases the energy of the particles that make up the substance

What two things can heating a substance do?

1. Raise its temperature

2. Change the state of the substance

What three factors determine the temperature change of a system

1. Mass of substance being heated

2. Type of material (Specific heat capacity)

3. Energy inputted into the system

State the equation used to calculate the temperature change when a substance is heated. Give appropriate units

change in thermal energy =mass × specific heat capacity ×temperature change

Define specific heat capacity

The amount of energy needed to increase the temperature of 1kg of a substance by 1°C

Describe how the internal energy and temperature of a substance changes when a change of state occurs

• The internal energy of the substance will be increased or decreased

• The temperature of the substance will remain constant

Define specific latent heat.

The amount of energy needed to change the state of 1kg of a substance with no change in temperature

State the equation for the energy required to change state. Give appropriate units.

Energy to change state (J) = mass(kg) × specific latent heat (j/kg)

What is the specific latent heat of fusion?

The energy required to change 1kg of a substance from solid state to liquid state without a change in temperature

What is the specific latent heat of vaporisation?

The energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature