Heating and cooling.
Touch something hot and your senses immediately tell you to pull your hand away. Hotness is about the amount of heat energy and object has.
A spark from a firework may be very hot, but it will not hurt very much because it does not contains a lot of heat energy.
Temperature and heat
Heat and temperature are not the same.
Temperature is a measure of how hot or col. Something is. It is measured in degrees Celsius (C). Temperature is measured with a thermometer.
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Heat Is the transfer of energy from a higher temperature object to a lower temperature object. It is measured in joules (J) or Kilojoules (KJ).
You already know that solids, liquids and gases are made up of tiny particles. These particles are moving about all the time. The more energy the particles have, the more they move about. The opposite is also true: as they lose energy, they move about less. This change in energy is what heat is.
As a solid cools, heat energy is removed. The particles will move more and more slowly until they stop moving altogether. The temperature at which the particles stop moving is called absolute zero. Absolute zero is the temperature at which a material has no heat energy. This temperature is -273'
Heat is about particles
You have learnt that everything is made of particles called atoms and molecules. They are constantly on the move, either vibrating or moving freely. It is the motion of particles that creates from of energy called heat. The movement of particles is affected by temperature. The higher the temperature, the faster particles move. This is know as the kinetic theory.
The kinetic theory can help explain how substances behave.
The loss or gaining of heat can change the state of matter.
Melting
If a solid is warmed, its particles move faster until some break free and become part of a liquid.
Evaporation
If heat is applied to a liquid, the particles move faster still. At the surface the faster particles break free to from a gas above it.
