3.2 - Internal Energy & 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 the temperature

2. Change the state of the substance

What three factors determine the temperature change of a system?

1. Mass of a substance being heated

2. Type of material (specific heat capacity)

3. Energy inputted into the system

Define specific heat capacity

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

State the equation used for specific heat capacity. Give appropriate units.

• ΔE = m × c × Δθ

• energy (J) = mass (kg) × specific heat capacity (J/kg°C) × temperature (°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 specific latent heat. Give appropriate units.

• energy to change state = mass × specific latent heat

• energy (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 a liquid state without a change in temperature.

What is the specific latent heat of vaporization?

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