Sources of Heat

As you have learned, food has energy stored in it which can be released as heat. Many other substances contain similar energy sources. Fuels are a good example. Solid fuels, such as coal, liquid fuels, such as gasoline and oil, and gaseous fuels, such as propane and natural gas, such as propane and natural gas, all contain chemical energy. This chemical energy can be released as heat through the chemical process of burning. Just as an automobile engine burns fuel, your body burns food in the process of digestion. (Digestive burning releases the heat gradually, so there is no damage to your body.) What foods have you eaten today to supply the energy your body needs? What would happen if you missed some meals? 
If the particles in a substance move more quickly, the average energy increases, and the temperature of the substance goes up. You can use the push or pull of a mechanical force to make the particles of a substance move more quickly. Rub your hands together for 30 s, then place your palms on your cheeks. The heat you feel is the result of a mechanical force called friction. Often, lubricants, such as oil, are used to decrease friction and the amount of heat created in machines.
Nuclear Reactions
If you have been outside on a summer day, you have felt the heat from the Sun. The Sun produces this heat through a nuclear reaction. Inside the Sun, atoms of hydrogen are joined together to form a large atom, helium. In this process, called fusion, a small amount of the mass of the hydrogen atoms is transformed into energy. The energy release uses Albert Einstein's famous formula, E=mc². (in the formula, E stands for energy in joules, m stands for mass in kilograms, and c stands for the speed of light in metres per second.) Technologists can also create nuclear reactions through a process called fission. In a fission nuclear reaction, atoms of a material like uranium are split into smaller atoms. This splitting also causes a small amount of mass to be transforms into energy. Controlled nuclear fission can be carried out in a nuclear reactor, such as the Canadian-designed CANDU reactor.
As electricity moves through a wire, it causes the particles in the wire to move. If the particles in a substance move more quickly, the average energy increases, and the substance gets hotter. Some metals release more heat than others when electricity passes through them. For example, iron releases more heat then copper. In order for electricity to be used as a source of heat, we must first produce the electricity. There is more than one way to produce electricity. In Canada, we are lucky to have many large river systems. The energy is moving water can be used to produce hydroelectricity. Much of our electricity is also produced at generating stations that burn fuels such as coal, oil, or natural gas, or at nuclear generating stations. Do you know where electricity you use comes from or how it is created?
Self Check

  1. List the ways that heat can be produced. Give an example of how each is used in your daily life. 
  2. In each of the following situations, state the type of energy that is a source of heat. 
    1. a) An iron is used to press clothes. 
      b) A match burst into flames. 
      c) A greenhouse produces tropical plants. 
      d) A toaster is used in preparing breakfast. 
      e) A nail becomes warm as it is pounded into a board. 
      f) The engine of a gasoline mower overheated after operating without oil. 
Journal Entry
Imagine a technological breakthrough in which a totally new and cheap source of heat is discovered. How would it affect you? How would it affect business and industry? 

' From Heat and Temperature, ITP Nelson. © Copyright 1997 
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