Page 124 - Physics - XI

Heat lost by solid = (m – m ) s (T – θ) = ______ cal
3
2
Here, s is the specifi c heat of the solid which is to be determined.
Since, heat lost = heat gain.

∴ (m – m ) s (T – θ) = [W + (m – m ) (θ – t)]
3 2 2 1
[W (m m )( t )]
or s = 2 1
(m m )(T )
3 2
= ______ cal g °C –1
–1

Result
Specifi c heat capacity of a given solid by method of mixture is ______ cal g °C .
–1
–1
Precautions

1. Suffi cient water should be taken in a hypsometer.
2. Solid should be dropped quickly, but gently without splashing water in a calorimeter.

3. Calorimeter should be polished from outside to avoid excessive radiation losses.
4. Solid should have no chemical reaction with water.
5. Temperature of cold water should not be below the dew point.

6. Final temperature of the mixture should be noted after stirring.

Sources Of Error

1. Some heat is lost while transferring hot solid into a calorimeter.
2. Some heat is lost in conduction, convection, and radiation in spite of maximum precautions.

VIVA VOCE

Q1. Why are the contents of a calorimeter stirred continuously till steady state is reached?
Ans. So that all parts of mixture may have the same temperature.

Q2. Give the S.I. units of specifi c heat.
Ans. The S.I. units of specifi c heat is J kg K .
–1
–1
Q3. Defi ne heat.
Ans. It is the energy which produces the sensation of warmth.

Q4. What is the diff erence between heat and temperature?
Ans. Heat is a form of energy while temperature is the degree of hotness of body.

Q5. Defi ne specifi c heat of a substance.
Ans. It is defi ned as the amount of heat required to raise the temperature of unit mass of substance
through 1 °C.

Q6. What material is a calorimeter made of?
Ans. It is generally made of copper.

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