Heat can be transferred from place to place byconduction,convectionandradiation. Dark matt surfaces are better at absorbing heat energy than light shiny surfaces. Heat energy can be lost from homes in many different ways and there are ways of reducing these heat losses.

Infrared radiation

All objects emit (give out) and absorb (take in) thermal radiation, which is also called infrared radiation. The hotter an object is, the more infrared radiation it emits.

Light from the sun reaching earth

Infrared radiation is a type of electromagnetic radiation, which involves waves rather than particles. This means that, unlike conduction and convection, radiation can even pass through the vacuum of space. This is why we can still feel the heat of the Sun, although it is 150 million km away from the Earth.

Some surfaces are better than others at emitting and absorbing infrared radiation. This table summarises the differences.

Comparison of surfaces abilities to reflect and absorb radiation

Type of surfaceAbility to emit infrared radiationAbility to absorb infrared radiation dark, matt (dull) good good light, shiny poor poor

Light, shiny surfaces are also good reflectors of infrared radiation.

Kinetic theory

The kinetic particle theory explains the properties of the different states of matter. The particles in solids, liquids and gases have different amounts of energy. They are arranged differently and move in different ways.

This table summarises the arrangement and movement of the particles in solids, liquids and gases, and shows simple diagrams of the arrangement of the particles that you should be able to recognise.

Diagram of particle arrangement and movement

SolidLiquidGas Arrangement of particles

close together

regular pattern

close together random

far apart

random

movement of particles vibrate about a fixed position move around each other move quickly in any direction diagram

Solids

The table shows some of the properties of solids and why they are like this.

Property of solidsWhy they are like this They have a fixed shape and cannot flow The particles cannot move from place to place They cannot be compressed or squashed The particles are close together and have no space to move into

Liquids

Some of the properties of liquids and why they are like this

Property of liquidsWhy they are like this They flow and take the shape of their container The particles can move around each other They cannot be compressed or squashed The particles are close together and have no space to move into

Gases

Some of the properties of gases and why they are like this

Property of gasesWhy they are like this They flow and completely fill their container The particles can move quickly in all directions They can be compressed or squashed

The particles are far apart and have space to move into

onduction

Heat energy can move through a substance by conduction. Metals are good conductors of heat but non-metals and gases are usually poor conductors of heat. Poor conductors of heat are called insulators. Heat energy is…