• Light, shiny surfaces are good            of infrared radiation.

• A thin, flat object will radiate heat energy              than a fat object. 

• The particles in a solid are held next to each other in fixed positions .
• They vibrate about their fixed positions so the solid keeps its own shape.

• The particles in a liquid are in contact with each other. 
• They move about at random. So a liquid doesn’t have its own shape and can flow.

The particles in a gas move about at random much faster. So There are on average , much further apart from each other than in a liquid. So the density of a gas is much less than that of a solid.

• Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.

• Liquids and gases 

It becomes less dense.

• Evaporation is when a liquid turns into a gas.

• Condensation is when a gas turns into a liquid.

• Evaporation can be increased by:

• increasing the surface area of a liquid,
• increasing the liquids temperature,
• by creating a draught of air across the liquids surface.

• Condensation on a surface can be increased by 

• increasing the area of surface ,
• reducing the temperature of the surface.

the rate at which an object transfers energy depends on its design. 

The design factors that matter are: 

the materials the object is in contact with 

the object’s shape

the objects surface area 

• loft insulation
• cavity wall insulation
• double glazing
• draught proofing
• aluminium foil behind radiators.

Power (in watts) = 

energy transferred (in joules)  

time taken (in seconds)

Efficiency =

useful power out     x 100  

total power in