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Calorimetry Heat is a form of energy and thus, can be converted into other forms of energy (like mechanical energy, electrical energy, etc.) and vice versa. We use heat for various purposes, like cooking, etc. The measure that is used for detecting the degree of hotness of a substance is called temperature. 1. Every substance is made up of matter, which is in turn made up of atoms and molecules. These atoms and molecules possess kinetic energy and are constantly in motion. 2. We know that heat is a form of energy. Thus, when we heat a substance, we provide energy to it. This added energy increases the kinetic energy of the molecules and, consequently, the temperature of the substance. 3. The total kinetic energy of all the molecules in a substance is called heat and the increase in average kinetic energy of its molecules is called temperature. The S.I. unit of heat is joule (J) and the S.I. unit of temperature is kelvin (K). Heat depends upon the mass of a substance while temperature does not. Let us differentiate between heat and temperature. Heat The total kinetic energy of all the molecules in a substance is called heat. It depends upon the speed, number, size or mass and type of particles in a substance. The S.I. unit of heat is joule (J) Temperature Temperature is the measure of the degree of hotness of a substance. It does not depend upon the size or mass of an object. The S.I. unit of temperature is kelvin (K). Relation between degree Celsius and Kelvin T K = 273 + t C T K=273+t C t C = T K 273 t C =T K-273 Specific Heat The quantity of heat required to raise the temperature of unit mass of a substance by 1 C Unit of Specific Heat In SI systems Joules per kilogram per degree J/kg C or J/kg-K In CGS systems Joules per gram per degree J/g C or J/g-K Heat capacity or thermal capacity The amount of heat energy required by an object to raise its temperature by 1 oC is known as its hear capacity. Thus, Heat Capacity, C' = Amount of heat energy supplied Rise in temperature = H r Heat Capacity, C'=Amount of heat energy suppli Relationship between heat capacity and specific heat capacity Heat capacity, C' = Mass, m Specific heat capacity, C Heat capacity, C'=Mass, m Specific heat c
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