Calorimetry: Concept of Heat, Law of Calorimetry ,Specific Heat, Latent Heat. Application of High Specific Heat of Water. Application of High Latent Heat of Water. Concept of Calorimetry. Numericals on Calorimetry. Deference between Heat and Temperature.

## Exercise 11 A

Question 1

Define the term heat.

The kinetic energy due to random motion of the molecules of a substance is known as its heat energy.

Question 2

Name the S.I. unit of heat.

joule (J)

Question 3

Define the term calorie. How is it releated to joule?

One calorie of heat is the heat energy required to raise the temperature of 1 g of water from 14.5oC to 15.5 oC.

1 calorie = 4.186 J

Question 4

Define one kilo calorie of heat.

One kilo-calorie of heat is the heat energy required to raise the temperature of 1 kg of water from 14.5oC to 15.5oC.

Question 5

Define temperature and name its S.I. unit.

The quantity which determines the direction of flow of heat between two bodies kept in contact is called temperature.

S.I. unit kelvin (K).

Question 6

State three differences between heat and temperature.

 Heat Temperature The kinetic energy due to random motion of the molecules ofa substance is known as its heat energy. The quantity which determines the direction of flow of heat between two bodies kept in contact is called temperature. S.I. unit joule (J). S.I. unit kelvin (K). It is measured by the principle of calorimetry. It is measured by a thermometer.

Question 7

Define calorimetry.

The measurement of the quantity of heat is called calorimetry.

Question 8

Define the term heat capacity and state its S.I. unit.

The heat capacity of a body is the amount of heat energy required to raise its temperature by 1oC or 1K.

S.I. unit is joule per kelvin (JK-1).

Question 9

Define the term specific heat capacity and state its S.I. unit.

The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of unit mass of that substance through by 1oC (or 1K).

S.I. unit is joule per kilogram per kelvin (J kg-1K-1).

Question 10

How is heat capacity of a body releated to specific heat capacity of its substance?

Heat capacity = Mass x specific heat capacity

Question 11

State three differences between the heat capacity and specific heat capacity.

Heat capacity of the body is the amount of heat required to raise the temperature of (whole) body by 1whereas specific heat capacity is the amount of heat required to raise the temperature of unit mass of the body by 1.

Heat capacity of a substance depends upon the material and mass of the body. Specific heat capacity of a substance does not depend on the mass of the body.

S.I. unit of heat capacity is and S.I. unit of specific heat capacity is.

Question 12

Name a liquid which has the highest specific heat capacity.

Water has the highest specific heat capacity.

Question 13

Write the approximate value of specific heat capacity of water in S.I. unit.

Specific heat capacity of water=4200 J kg-1 K-1

Question 14

What do u mean by the following statement;

(i) The heat capacity of a body is 50 J/k ?

(ii) The specific heat capacity of copper is  0.4 J/g/K ?

(i) The heat capacity of a body is 50JK-1 means to increase the temperature of this body by 1K we have to supply 50 joules of energy.

(ii) The specific heat capacity of copper is 0.4Jg-1K-1 means to increase the temperature of one gram of copper by 1K we have to supply 0.4 joules of energy.

Question 15

Specific heat capacity of a substance A is 3.8 J g-1 K-1 and of substance B is 0.4 Jg-1 k-1. Which substance is a good conductor of heat? How did you arrive at your conclusion?

The specific heat capacity of substance B is lesser than that of A. So, for same mass and same heat energy, the rise in temperature for B will be more than that of A. Hence, substance B is a good conductor of heat.

Question 16

Name two factors on which the heat energy librated by a body on cooling depends.

Change in temperature and the nature of material

Question 17

Name three factors on which the heat energy absorbed by a body depends and state how does it depend on them

The quantity of heat energy absorbed by a body depends on three factors :

(i)Mass of the body – The amount of heat energy required is directly proportional to the mass of the substance.

(ii)Nature of material of the body – The amount of heat energy required depends on the nature on the substance and it is expressed in terms of its specific heat capacity c.

(iii)Rise in temperature of the body – The amount of heat energy required is directly proportional to the rise in temperature.

Question 18

Write the expression for the heat energy Q received by m kg of a substance of specific heat capacity c J kg-1 K-1 when it is heated through toC.

The expression for the heat energy Q

Q= mct (in joule)

Question 19

Same amount of heat is supplied to two liquid A and B. The liquid A shows a greater rise in temperature. What can you say about the heat capacity of A as compared to that of B?

Heat capacity of liquid A is less than that of B.

As the substance with low heat capacity shows greater rise in temperature.

Question 20

Two blocks P and Q of different metals having their mass in the ratio 2:1 are given same amount of heat. Their temperatures rise by same amount, compare their specific heat capacities Question 21

What is the principle of method of mixture? What other name is given to it? Name the law on which this principle is based.

The principle of method of mixture:

Heat energy lost by the hot body = Heat energy gained by the cold body.

This principle is based on law of conservation of energy.

Question 22

A mass m1 of a substance of specific heat capacity c1 at temperature T1 is mixed with a mass m2 of other substance of specific heat capacity c2 at a lower temperature T2. Deduce the expression for the temperature of mixture. State assumption made, if any.

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