Heat

Objectives

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The Students Will be able - To list out the sources of heat - To define heat - To distinguish hot and cold objects - To define temperature - To differentiate heat and temperature - To understand the conditions for thermal equilibrium - To understand why thermal expansion take place in solids - To list out the practical applications of thermal expansion in day - to - day life

Summary

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- The main source of heat is sun, we can obtain heat from combustion, friction, and electricity. - Heat is an energy that raises the temperature of a thing by causing the molecules in that thing to move faster - Heat is the total Kinetic energy of constituent particles of objects. - SI unit of Heat is joule (J). - The measurement of warmness or coldness of a substance is known as its temperature. - SI unit of temperature is kelvin. - Temperature determines the direction of flow of heat when two bodies are placed in contact. - Two objects are said to be in thermal contact if they can affect each other’s temperature. - Thermal equilibrium exists when two objects in thermal contact no longer affect each other’s temperature. - Most substances expand when heated and contract when cooled. The expansion of a substance on heating is called the thermal expansion of that substance. - A solid has a definite shape, so when a solid is heated, it expands in all directions i.e., in length, area and volume, all increase on heating.