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Heat
Heat is a form of energy. It does not take up any space. It does not weigh anything. It can be used to do work when we see an automobile speeding down a road, we can be sure that it is being driven by the heat of burning gasoline.
There are many ways of producing heat. Fire, friction and electricity are three of them. All the ways of producing heat, however, would not keep the Earth warm enough for us to live on it if it were not for the Sun. The Sun has given the earth heat for millions of years.
Heat travels much better through metals. They are good conductors of heat. Wool, asbestos and air are three of the many poor conductors of heat. We use poor conductors to shut heat in or shut it out.
Most substances expand or get bigger when they are heated. Heat brings about many other changes in materials. Heating some solid substances make them melt. Heating liquids make them change to a vapour or gas.
Cold means absence of heat. We can cool something only by making heat travel out of it. In a refrigerator we do not put cold into the food. We take heat out. Knowing how heat can be produced, how it travels, and what kinds of changes it brings about is important for all of us.
Very long ago people came to the idea of heating their homes. The idea of heating with fire is not new. Thousands of years ago the cave- men used fire for heating. The Romans worked out a way of heating all the rooms in their houses with one fire. The fire was built in a room called the antrium. “Antrium” means “black room”. It got its name from the soot that coated its walls. From this room hot air was carried through pipes to the rest of the house. Heating all the rooms of a building from one source of heat is called central heating.
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