Notes

When our country was very young, homes had big fireplaces. The fireplaces were used both for cooking and for heating.
Today, people keep the heating fires in furnaces. The heat energy goes through ducts to heat the air in their homes. When people are cold, they can turn up the thermostat and get heat.
Fire cannot burn by itself. It needs fuel and an invisible gas called oxygen. It also needs heat energy from something else to start the burning. For example: when you light a candle, a match or lighter is needed to start the flame. When you put a candle out you cover the flame so it no longer gets oxygen.
Fuel for a fire can be many things. Some fuels are solid. Wood and coal are solid fuels. Other fuels are liquid. Oil and gasoline are liquid fuels.
Some gases are fuels. Many homes are heated by burning a special gas in a furnace. It is called natural gas. Another gas that burns is butane. It is a source of heat for stoves and furnaces.
All of the fuels you have learned about are natural resources. Some natural resources can be replaced. Wood comes from our forests that can be replanted. Oxygen comes from growing plants. Coal, oil, and natural gas cannot be replaced. Your job will be to help take care of these natural resources so they will last.
Remember that no fuel can burn without oxygen. Oxygen is a gas that causes things to burn. It is in the air you breathe.
You have learned that fire needs two things to burn. They are fuel and oxygen.
When fuels are burned, products are left. The most important and useful product is heat. Other products are gases that get into the air. Some of these gases make the air dirty.
Burning solid fuels leaves solid products. When wood is burned, ashes are left. Cinders are left from burning coal.