When you walk under the noonday sun, you feel that your skin becomes hot. This is due to the sun's heat that reaches the Earth. You can feel heat but you cannot see it. Heat has no mass. It has no weight. And it does not occupy space. Therefore, it is not matter. It not matter, then what is it?
People use heat in many ways. In the home, it is used for cooking, drying clothes and making the house warm on cold days. In industry, it is used to melt, cut and shape metals, to process foods and other products,and turn to run machines. Heat does work. So, it is a form of energy.
Some objects are hot. Others are cold. To illustrate the transfer of heat, place a spoon, nail, pencil, plastic ruler and rubber band in boiling water alternately. What do you think will happen when a hot object comes in contact with a cold object? This illustration will show that when a cold object comes in contact with a hot object, the cold object becomes hot, too.
Some energy from the hot object transferred to the cold object. This energy that is transferred from the warmer to the cooler object is called heat. The direction of heat transfer is always from the warmer object to the cooler object. You feel warm when you stand near a stove while cooking food because some heat from the stove transfers to you. Your body is very much cooler in comparison with the heat from the stove.
How heat is produced?
All things are made up of very tiny particles called atoms and the molecules they form. These are always moving. Energy is produced by the motion of these particles and is called thermal energy. The faster the particles on an object move, the more thermal energy that objects has. How heat is produced? Two ways are describein this article, by rubbing and by burning.
Rubbing your hands together made the particles in them move faster than before. This explains why our hands felt warm. Then same thing happened to sandpaper that is rubbed in a wooden block. All objects have energy because of the motion of their particles. Heat is produced when that energy transfer from a warmer object to a cooler object.
Observe the tip of a match. It is covered with chemicals that produce fire. Look at the side of the matchbox. It is also made on some chemicals. When the tip of the match is rubbed against the side of the box, the heat produced by rubbing makes the chemicals of the match combine rapidly with oxygen in the air, causing burning.
Burning is also called combustion. Combustion is a chemical reaction that produces heat and light. It is also a result of rapid oxidation. There are three basic conditions that are necessary before burning can take place. (1) There must be a material that can burn (fuel) such as wood, (2) The temperature of the material must be raised to the degree at which the material starts to burn. This is called kindling or ignition temperature, and (3) there must be a good supply of oxygen.
A fire that started by itself called spontaneous combustion happens when oxidation produces heat in materials such as methane gas stored in a closed space with poor ventilation. Since the heat cannot escape, the gas reaches its ignition temperature and suddenly burst into flames.
note: originally posted at Exposeknowledge.com under the same author.