![]() When someone cooks meat using a closed container, no gas is allowed to escape. When water is being boiled in an open sauce pan, vapour is allowed to escape. In all the above, there exists energy exchanges and such things are called systems. List down three utensils used for cooking food in your homes.Describe how these utensils are used to cook the food. Further increase of heat supplied means that extra energy is absorbed by the molecules of the gas, hence expanding and pushing the tyre. When a gas is heated its temperature increases and hence the average speed of molecules also increases increasing the internal energy of the gas. This energy depends on the temperature of the gas. The energy possessed by the molecules of the gas is called internal energy of the gas. The same thing happens with the balloon in air. As a result, they collide frequently with the walls of the tube and therefore exert high pressure on the walls and the tube bursts. When the bicycle tube is left exposed to sunshine, it gets heated and the molecules in the gas gain energy and hence its kinetic energy increases. In this unit, we shall be interested in studying the behaviour of molecules in matter. Note down your observation in your exercise books.You already know the characteristics of the three states of matter that is solids, liquids and gases. ![]() Similarly explain why a balloon full of air bursts as it rises in the atmosphere.In groups of five, explain why an inflated bicycle tube bursts when it is left on sunshine for a very long time.This total heat energy supplied is called thermal energy. Therefore, when this saucepan is heated, the heat gained is used to boil off the water and extra work is done to push the sauce pan cover. You have already seen in your early secondary that heat is a form of energy. When water boils, the vapour pushes the cover off the sauce pan. Have you ever boiled water on a sauce pan with a cover?ĭescribe what happens to the cover when water boils? This means that particles of a body vibrate because of energy they have. Remember that heat is the measure of total internal energy of a body. The systems to discuss in this unit include refrigerators, heat pumps, car engines. Heat can be changed / transformed from one form to another.So, if in a system heat changes from one form to another, its called thermal dynamic system.* explain thermodynamic processes in heat engines. * state the second law of thermodynamics. * explain the work done by the expanding gas. By the of this unit, the learner should be able to evaluate applications of first and second laws of thermodynamics in real life.īy the end of this unit, I will be able to:ĭifferentiate between Internal energy and total energy of a system.
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