Heat Energy Heat is a form of energy It flows from one place to another due to temperature difference between two points Sources of heatSome sources of heat are a Sun b Friction c Chemical reaction d Electricity e Burning of fuels like wood f Conversion of other forms of energy 1 Sun energy The sun is the primary source of heat energy 2 Friction This is a force that occurs when two surfaces are in contact 3 Electrical energy This is an energy that is produced from electricity 4 Chemical reaction Energy can be produced when two chemicals are mixed together Transfer of heat Transfer of heat refers to the flow of heat or ways of spreading heat There are three major ways of transferring heat They are 1 Conduction 2 Convection 3 Radiation 1 Conduction This the flow of heat to a metal Example When one end of a spoon is put into a flame You will discover that the other end will get heated Heat is transferred from the pot to the spoon 2 Convection This the flow of heat to a liquid Example When you put a kettle of water on an electric heater Heat will circulate in the liquid through convection Radiation This type is spread through the heat from the sun or lighted lamp Effects of heat on objects 1 Rise in temperature 2 Expansion of the substance 3 Change of shape 4 Change of color of the substances 5 Change of state 6 Formation of new substances Uses of heat at home 1 For cooking 2 For drying clothes 3 For warming 4 For warming our body 5 For ironing Uses of heat in industries 1 For melting metals 2 In sterilization process 3 To form new substances through chemical reactions 4 In recycling industry