Heat Capacity: Did you know that earlier the unit of heat was calorie? One calorie was defined to be the amount of heat required to raise the temperature of 1g of water by 1 C. Read the article to know what is the specific heat capacity of water and how it is defined. Clearing these topics will help you in scoring good marks in the examination.
What is Heat Capacity?
NCERT says that the quantity of heat required to warm a given substance depends on its mass, m, the change in temperature, ΔT and the nature of substance. Thus heat capacity is defined as, ''The change in temperature of a substance, when a given quantity of heat is absorbed or rejected by it, is characterised by a quantity called the heat capacity of that substance.''
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What is Specific Heat Capacity?
Specific heat capacity of a substance is defined as, ‘’Every substance has a unique value for the amount of heat absorbed or rejected to change the temperature of unit mass of it by one unit. This quantity is referred to as the specific heat capacity of the substance. The specific heat capacity is the property of the substance which determines the change in the temperature of the substance (undergoing no phase change) when a given quantity of heat is absorbed (or rejected) by it. It is defined as the amount of heat per unit mass absorbed or rejected by the substance to change its temperature by one unit. It depends on the nature of the substance and its temperature. The SI unit of specific heat capacity is J kg–1 K–1.’’
What is the formula of Specific Heat Capacity?
Q = C m ∆t
Where
Q = quantity of heat absorbed by a body
m = mass of the body
∆t = Rise in temperature
C = Specific heat capacity of a substance depends on the nature of the material of the substance.
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What is the Specific Heat Capacity of Water?
The specific heat of water varies slightly with temperature. Students might be aware that the value of specific heat capacity is approximately 4.2 J/g°C. Thus this means that it takes 4.2 joules of energy to raise 1 gram of water by 1 degree Celsius. It has been observed that the temperature of water increases as it absorbs heat and decreases as it releases heat.
What is Molar Specific Heat Capacity?
If the amount of substance is specified in terms of moles m, instead of mass m in kg, we can define heat capacity per mole of the substance by heat capacity divided by mole, where C is called molar specific heat capacity.
What is Molar Specific Heat Capacity at Constant Pressure?
If the gas is held under constant pressure during the heat transfer, then it is called the molar specific heat capacity at constant pressure and is denoted by Cp.
What is Molar Specific Heat Capacity at Constant Volume?
If the volume of the gas is maintained during the heat transfer, then the corresponding molar specific heat capacity is called molar specific heat capacity at constant volume and is denoted by Cv.
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