Transfer of Energy

All objects emit and absorb radiation.

The hotter an object the more infrared radiation it radiates in a given time.

Dark, matt surfaces are good absorbers and emitters of infrared.

Light, shiny surfaces are poor absorbers and emitters of infrared.

Light, shiny surfaces are good reflectors of infrared.

Solid:The particles in a solid are held next to each other in a fixed position, they vibrate and the solid keeps it's shape.

Liquid: The particles in a liquid are in contact with each other. They move about at random. So the liquid doesn't keep it's own shape and can flow.

Gas: The particles in gas move at random much faster. They are much further apart than in a liquid. The density of gas is much lowe than that of a liquid of solid.

The particles in solids, liquids and gases have different amounts of energy.

Gas: Most amount of energy.

Liquid: Mediocre amount of energy.

Solid: Least amount of energy.

Conduction:

Metals are good conductors as they contain free electrons.

• Upon heating these electrons diffuse and collide with other free electrons in the cooler part of the metal.

• As a result kinetic energy is transferred to this other electrons.

So energy is transferred from the hot end of the rod to the cooler end.

In non-metals the energy is transferred by the vibration of particles.

Convection: When a fluid (liquid or gas) is heated a convection current can occur. Hot fluid rises as it is less dense as particles separate out. Cold are sinks as it is more dense than the hot fluid.

Evaporation is when liquid turns into a gas. Cooling by evaporation is due to faster moving molecules escaping from the liquid lets thermal energy 'escape'.

Condensation is when a gas turns to  liquid.

Condensation on a surface can be increased by:

Increasing the area of the surface

Lowering the temperature.

The bigger the temperature difference between an object and it's surroundings, the faster energy is transferred.

Specific heat capicity is the amount of energy required to change the temperature of one kilogram of a substance by one degree Celsius.

E= m  x c x θ

E: Energy transferred in joules.

M: Mass in kilograms

θ: Temperature change in degree Celsius.

C: Specific heat capacity in J/Kg °C

U-Values measure how effective a material is as an insulator.

The lower the U-value, the better insulator a material is.

Solar panels may contain water that is heated by radation from the sun. This water may then be used to heat buildings or provide domestic hot water.