FRANK Solutions for Class 10 Physics Chapter 5.1 - Calorimetry

Chapter 5.1 - Calorimetry Exercise 233

Question 1

What do you mean by thermal energy?

Solution 1

Thermal energy is energy that is powered by a heat source. For e.g.: an electric heater generates thermal energy that can be used to warm a cold room in the winter.

Question 2

Name the physical quantity that measures the degree of hotness.

Solution 2

Temperature is the physical quantity that measures the degree of hotness.

Question 3

A substance is heated gradually. Does its energy increase or decrease?

Solution 3

Its energy increases on heating.

Question 4

Why do the molecules of a gas move about freely?

Solution 4

Gas molecules have very weak or no bonds at all and the spaces between gas molecules are very large. So, the molecules of a gas move about freely.

Question 5

Name the two scales used for measuring temperature.

Solution 5

Two scales for measuring temperature are
i.    Celsius scale
ii.    Fahrenheit scale

Question 6

What kind of thermometer is commonly used?

Solution 6

'Liquid-in-glass' kind of thermometer is commonly used.

Question 7

What is the other name of Doctor's thermometer?

Solution 7

Doctor's thermometer is also called Clinical thermometer.

Question 8

Express the melting point of ice on the Celsius scale and the Fahrenheit scale.

Solution 8

Question 9

Which scale of temperature is commonly used and why?

Solution 9

Celsius scale and Fahrenheit scale are two commonly used scales of temperature because the former is based on the freezing point of water as 0^oC and boiling point of water as 100^oC. The same points on the Fahrenheit scale are 32^oF and 212^oF.

Question 10

What is the normal body temperature of a healthy person on the Celsius scale?

Solution 10

The normal body temperature of a healthy person is 37^oC.

Question 11

Write down a relationship to convert temperature on the Fahrenheit to Celsius scale.

Solution 11

Question 12

Is heat a form of energy?

Solution 12

Yes, heat is a form of energy.

Question 13

What are the upper and lower fixed points on the Fahrenheit scale?

Solution 13

Lower fixed point = 32^oF
Upper fixed point = 212^oF

Question 14

Describe the Celsius scale of temperature.

Solution 14

In Celsius scale, melting point of ice and boiling point of water are referred as "lower fixed point" and "upper fixed point" respectively. The temperature difference between the reference points is divided into 100 divisions and each division is called "one degree Celsius" (1^oC). Thus, the melting point of ice is taken as 0^oC and the boiling point as 100^oC.

Question 15

Which represents a greater temperature rise, 20⁰C or 20⁰ F?

Solution 15

Question 16

Express -40⁰C on the Fahrenheit scale.

Solution 16

Question 17

Express 212⁰F on the Celsius scale.

Solution 17

Question 18

What do you understand by the term 'temperature'?

Solution 18

Temperature is a physical property that quantitatively expresses the common notions of hot and cold. It is the degree of hotness or coldness of a body or environment.

Question 19

Distinguish between heat and temperature.

Solution 19

Question 20

What is the SI unit of heat and temperature?

Solution 20

The SI unit of heat energy is joule (J).

Question 21

Define 1 joule.

Solution 21

1 joule is the amount of heat required to raise the temperature of 1 kg of a substance, that has specific heat capacity 1J/kgK, through 1^oC.

Question 22

Which is bigger: 1 joule or 1 calorie?

Solution 22

1 J = 4.2 cal. So, 1 joule is bigger than 1 calorie.

Question 23

Name the instrument used to measure temperature.

Solution 23

A thermometer is used to measure temperature.

Question 24

(i) Plot a graph taking ^oC on the Y-axis and the corresponding ^oF along the X-axis.
(ii) Plot a graph taking ^oF along the Y-axis and the corresponding ^oC on the X-axis.

Solution 24

Chapter 5.1 - Calorimetry Exercise 234

Question 1

Express the temperature of 0 K on the:
(a) Celsius scale
(b) Fahrenheit scale

Solution 1

Question 2

What is absolute zero?

Solution 2

Absolute zero is the temperature at which volume or pressure of an ideal gas becomes nil. It is 0 degrees on the Kelvin scale, which translates to -273^oC (or -459.4^oF).

Question 3

If the temperature of a body is 20⁰C, what will be the corresponding temperature on the Kelvin scale?

Solution 3

Question 4

Convert 37⁰C temperature to the Fahrenheit scale.

Solution 4

Question 5

Write the SI unit of:
(i) Amount of heat
(ii) Heat capacity
(iii) Specific Heat capacity

Solution 5

SI unit of:
i.    Amount of heat - joule
ii.    Heat Capacity - joule per Kelvin
iii.    Specific Heat Capacity - joule per kilogram per Kelvin

Question 6

A bucket contains 8 kg of water at 25⁰ C. 2 kg of water at 80⁰ C is poured into it. Neglecting the heat energy absorbed by the bucket, calculate the final temperature of water.

Solution 6

Question 7

What mass of a liquid A of specific heat capacity 0.84 J K^-1 and at a temperature 40⁰C must be mixed with 100 g of a liquid B of specific heat capacity 2.1 J g^-1 K^-1 and at 20⁰C, so that final temperature of mixture becomes 32⁰C?

Solution 7

Question 8

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

Solution 8

Specific heat capacity of water is 4200 Jkg^-1K^-1.

Question 9

The sp. Heat capacity of water is 4200 J kg^-1 K^-1. What information does this convey?

Solution 9

This means that 4200 J of heat is required to raise the temperature of 1kg of water by 1K.

Question 10

Give one example each where high specific heat capacity of water is used (i) In cooling, (ii) As heat reservoir.

Solution 10

(i) In cooling - Water is used in the cooling systems of automobiles and other engines.
(ii) As heat reservoir - In cold countries, water is used as a reservoir for wine and juice to avoid their freezing. The reason is that water can provide more heat to the bottles due to its high specific heat capacity. Hence, they do not cool down further to freeze.

Question 11

What is a calorimeter? Why is it made of copper? Give two reasons.

Solution 11

A calorimeter is a device used to measure the quantity of heat transferred to or from an object.
     It is made of copper because:
i.    Copper is a good conductor of heat so it attains the temperature of its contents in a very short time.
ii.    It has low specific heat (390 Jkg^-1K^-1). Therefore, it will take only a very little part of the heat energy given out in the experiment.

Question 12

A piece of iron of mass 2.0 kg has a thermal capacity of 966 J/⁰C. Find: (i) Heat energy needed to warm it by 15⁰C, and (ii) Its specific heat capacity in SI unit.

Solution 12

Question 13

Why do the farmers fill their fields with water on a cold winter night?

Solution 13

Farmers fill their fields with water on a cold winter night to protect the crops from frost. In the absence of water, if on a cold night the temperature of the surroundings fall below 0⁰C, then the veins of the plants shall freeze. Due to anomalous expansion of water, ice shall occupy more volume than water. As a result of this expansion, veins shall burst and crops shall be destroyed. But water sprinkled on the crops shall not allow the temperature of the veins to fall below 0⁰C.

Question 14

The temperature of 600 g of cold water rises by 15⁰C when 300 g of hot water at 50⁰C is added to it. What was the initial temperature of the cold water?

Solution 14

Question 15

Define the term 'heat capacity' and state its unit.

Solution 15

Heat capacity of a body is the quantity of heat required to raise its temperature by 1^oC. It depends upon the mass and the nature of the body.
Units: J/^oC or calorie/^oC

Question 16

Define the term 'specific heat capacity' and state its unit.

Solution 16

Specific heat capacity is the amount of heat required to raise the temperature of 1 kg of the substance by 1^oC.
Units: j/kgK or calorie/g ^oC

Question 17

0.5 kg of lemon squash at 30⁰C is placed in a refrigerator which can remove heat at an average rate of 30 Js^-1. How long will it take to cool the lemon squash to 5⁰C?(Sp. heat capacity of lemon squash = 4200 J kg^{-1 o}C^-1.)

Solution 17

Question 18

Describe a method to determine the specific heat capacity of a solid, like a piece of copper.

Solution 18

Question 19

Discus the role of high specific heat capacity of water with reference to climate in coastal areas.

Solution 19

The specific heat capacity of water (4200 J Kg^-1 K^-1) is about five times as that of sand. Due to which water takes long time to get heated up and equally long time to get cooled. Thus, large temperature difference between the land and the sea causes formation of land and sea breezes.

Question 20

State the principle of calorimetry.

Solution 20

Principle of Calorimetry:
When a hot body is mixed or kept in contact with a cold body, there is a transfer of heat from hot body to cold body such that
Total heat gained by colder body = Total heat lost by the hot body,
if there is no loss of heat to the surroundings.

Question 21

Water is used as an effective coolant. Give reason.

Solution 21

Water is used as an effective coolant since it has a high value of specific heat capacity (4200 J kg^-1K^-1).