What is HEAT?
Form of energy and measured in JOULES
Particles move about more and take up more room if heated – this is why things expand if heated
It is also why substances change from: solids liquids gases when heated
The temperature of an object tells us how HOT it is
Measured in degrees Celsius - °C
It is NOT the same as heat energy although the two quantities are related. e.g. a beaker of water at 60 °C is hotter than a bath of water at 40 °C BUT the bath contains more joules of heat energy
If an object has become hotter, it means that it has gained heat energy.
If an object cools down, it means it has lost energy
Heating and Cooling cont…
Heat energy always moves from: HOT object COOLER object
e.g.Cup of water at 20 °C in a room at 30°C - gains heat energy and heats up – its temperature rises
Cup of water at 20 °C in a room at 10°C loses heat energy and cools down – its temperature will fall.
Energy transfer Conduction Convection Radiation
Heat is transferred through a material by being passed from one particle to the next
Particles at the warm end move faster and this then causes the next particles to move faster and so on.
In this way heat in an object travels from: the HOT end the cold end
Occurs by the particles hitting each other and so energy is transferred.
Can happen in solids, liquids and gases,
Happens best in solids-particles very close together
Conduction does not occur very quickly in liquids or gases
Materials that conduct heat quickly are called conductors
All metals are good conductors of heat
Copper is a very good conductor of heat
Pans for cooking are usually made with a copper or aluminium bottom and plastic handles
Materials that conduct heat slowly or poorly are called insulators
Glass, wood, plastic and rubber are poor conductors (good insulators)