Synopsis On Heat

SYNOPSIS on HEAT Total energy if all the molecules are known as heat, S.I. unit is joule, calorie in C.G.S, BTU in British thermal unit Average kinetic energy of the molecules is known as temperature. Temperature scales are; Celsius (Centigrade), Fahrenheit, Kelvin, Rankin, thermometer is used to measure the temperature, 5 9 0 Scale Conversions: 0F to 0C ; C = (F – 32), C to 0F; F = C + 32, 5 9 0 C to K: K =C + 32, K to 0C; C = K – 32 The amount of heat required to raise the temperature 1 0C or 1K of I kg of a substance is known as specific heat. ΔQ = mcΔT or ΔQ = ncΔT ( for water 4.2J or 1 calorie ) The heat capacity is defined as the amount of heat required per unit increase in temperature The amount of heat required to change the state from solid to liquid without changing the temperature is known as latent heat of vaporization (3.6x105 J) The amount of heat required to change the state from liquid to gas without changing the temperature is known as latent heat of fusion. (2.5x106 J) Thermometry; the art of measuring temperature. Thermal expansion; expansion of substances on hearting Anomalous expansion of water: water contracts from 00C to 40C then expands Boyle’s law: volume and pressure of a gas of fixed mass are inversely proportional to each other provide the temperature is kept constant PV = K, P1V1 = P2V2 Charle’s law: volume and temperature of a gas of fixed mass are directly proportional V1 V2 V to each other provided the pressure of the gas is kept constant: = K, = T1 T2 T Law of heat exchange: heat lost = heat gain Conduction; is the process in which heat is transferred from one part of the body to the other due to without the actual movement of the molecule Convection; is the process in which heat is transferred from one part of the body to the other due to the actual movement of the molecule. Radiation; is the process in which heat is transferred from one part of the body to the other due to rays. Linear expansion; expansion of substances linearly on hearting L= L0(1+α ΔT), ΔL=L0 α ΔT Volumetric expansion; ; expansion of substances volumetrically on hearting V= V0(1+α ΔT), ΔV=V0 α ΔT In centigrade scale; Melting point of the ice is00C, boiling point of water 1000C,100 equal divisions In Fahrenheit scale; Melting point of the ice is320F, boiling point of water 2120F,180 equal divisions In Kelvin scale; Melting point of the ice is273K, boiling point of water 373K, 100 equal divisions Freezing point decreases on increasing pressure Boiling point increases on increasing pressure The change of state from liquid to gas on room temperature is called vaporization.

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