Temperature and Heat Definitions + Formulae

Temperature

The degree of how hot or cold a body is

Heat

A form of energy that causes a change in temperature when added to or removed from a system

Thermometric property

A physical property of a substance that changes measurably with a change in temperature

Heat Capacity

The heat needed to raise the temperature of an object by 1K

Formula for Heat Capacity

Heat energy = (specific heat capacity)(change in temperature)

Specific heat capacity

Amount of heat necessary to raise the temperature of 1kg of a substance by 1K

Formula for Specific heat capacity

Heat energy = (mass)(specific heat capacity)(change in temperature)

Latent heat

The amount of heat necessary to change the state of a substance without a change in temperature

Specific latent heat of fusion

The amount of heat necessary to change 1kg of a substance from a solid into a liquid without a change in temperature

Specific latent heat of vaporisation

The amount of heat necessary to change 1KG of a substance from a liquid into a gas without a change in temperature

Conduction

The movement of heat through a substance by transferring kinetic energy between adjacent particles which themselves do not move

(fire poker)

Convection

The movement of heat through a fluid by using circulating currents of fluid

(kettle)

Radiation

Transfer of heat by electromagnetic waves emitted by one body and absorbed by another

(toaster)

U- Value

The amount of heat per second passing through 1m^2 of a substance when there is a temperature difference of 1K between its ends ( Wm^-2 K^-1 = unit)

Solar Constant/Solar Irradiance

Average amount of the sun’s energy falling per second normally on 1m^2 of the earth’s atmosphere

Formula for latent heat

Heat energy = (mass)(latent heat)

What is the thermometric property of a thermocouple

Emf

What is the thermometric property of a mercury thermometer

Height of mercury

Why could two different thermometers give different readings in the same environment

They have different thermometric properties

Why is it necessary to have a standard thermometer

Different thermometers have different thermometric properties and therefore give different readings

What is a heat pump

Pump that transfers heat energy from one place to another

Describe the operation of a heatpump

• Liquid with a low boiling point circulates in a fridge through a series of pipes

• Liquid absorbs the latent heat from the air and evaporates causing a drop in temperature

• Gas is pumped outside where it condenses, releasing its latent heat causing an increase in temperature

Why is water an unsuitable thermometric property

It has a poor range and it is not very sensitive to heat

What makes a good thermometer

Low heat capacity

Sensitive

Good range to measure a large amount of temperatures