3.2 Internal energy and energy transfers
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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?
● Raise its temperature ● Change the state of the substance
What three factors determine the temperature change of a system?
● Mass of substance being heated ● Type of material (specific heat capacity) ● Energy inputted it 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 x specific capacity x change in temperature Energy (J), Mass (kg) specific heat capacity J/kg/°C, Temperature (°C)
Define specific heat capacity
The amount of energy needed to increase the temperature of 1kg of a substance by 1°C.
What is the specific heat capacity of water?
4,200 J/kg/°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 = mass x 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 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