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Heating and Cooling

Heat and temperature are not the same thing. We know this because heat is measured in Joules and temperature is measured in Degrees Celsius. Heat is energy whereas temperature is used to compare something for example we could say ice is cooler than tap water or our bodies are warmer than ice.

Substances can change state, usually when they are heated or cooled. E.g. water turns into water vapor (Steam) when it is heated, and turns into ice when it is cooled.

You can tell when it has changed state when the line on the graph straightens out. For example, on this graph the change of state is at 8 minutes.

Solids are better conductors than liquids and gases because the particles are closer together so they can transfer heat from each other faster.

Liquids and gases are good convectors because they are used in radiators which are commonly used household items. Liquids and gases are fluids because they can be made to flow. The particles in these fluids can move from place to place. 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 expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold.

Heat cannot travel through a vacuum through convection or conduction because there are no particles to pass the energy through. Heat energy can also be transferred as thermal radiation by waves. Shiny, Silver things are better reflectors than matte black things. Darker surfaces release more thermal energy than shiny surfaces, which means it cools down quicker, and absorbs the heat faster.

Some metals expand more than others due to differences in the forces between the atoms molecules. In metals such as iron the forces between the atoms are stronger so it is more difficult for the atoms to move around. In brass the forces are a little weaker so the atoms are free to move about more. These differences in contraction are used in a bimetallic strip, which is composed of a strip of brass laid alongside strip of Iron. When the strip is heated the brass expands more than the iron so the strip beds. It is used in devices such as fire alarms and circuit breakers to either make or break contacts in an electric circuit.

This is a diagram of heating and cooling when the wire gets heated it goes up when it gets cold it goes down.

heat/heating.txt · Last modified: 2016/05/19 14:20 by sykesn