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 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 substrate is heated, with units

∆E=mc∆T

Change in thermal energy (J) = Mass (Kg) x Specific heat capacity (J/Kg °C ) x temperature change (°C)

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, with units

energy to change state (J) = mass (kg) x specific latent heat (J/Kg)

What is the specific latent heat of fusion?

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