Matric Part 1/9th Class Physics Chapter 8 Long Question With Answer for Unit 8 Thermal Properties of Matter

Question # 1

Q no: 7 (B) Normal temperature of is 98.6 F. Convert it in the Celsius scale and .

Ans 1: Solution:
T_f=98.6°F
T_k=?
c=5/9 (98.6-30)
c=5/9 (66.6)
c= 37°C
T_k=c +273
T_k =310k

Question # 2

Briefly explain thermal expansion of liquids

Ans 1: Thermal expansion of liquid: there molecules of liquids are free to move in all directions within the liquid. On heating a liquid, the average amplitude of vibration of its molecules increases. The molecule's push each other and need more space to occupy. This account for the expansion of the liquid when heated. The thermal expansion in liquids is greater than solids due to the weak forces between their molecules. Therefore, the coefficient of volume expansion of liquids is greater than solids. Liquids have no definite shape of their own. A liquid always attains shape of container in which it is pored. Therefore, when a liquid is heated, both liquid and the container
Ans 2: Types:
- Apparent volume expansion
- Real volume expansion
Ans 3: Experiment: take a long-necked flask. Fill it with some colored liquid up to the mark A on its neck>Now start heating the flask from bottom. The liquid level first falls to b and then rises to C.
The heat first reaches the flask and its level falls to B. After sometime, the liquid begins to rise above B on getting hot. At certain temperatures it reaches at C. The rise in level A to C is due to the apparent expansion because of the expansion of the glass flask. Thus real expansion of the liquid is equal to the expansion because of the expansion of the glass flask. Thus real expansion of the liquid is equal to the volume difference between A and C in addition to the volume expansion of the flask. Hence
real expansion of the liquid= Apparent expansion of the liquid Expansion of the flask
BC+ AC+AB
The expansion of the volume of a liquid taking into consideration the expansion of the container also , is called the real volume expansion of the liquid. The real rate of volume expansion B, of a liquid is defined as the actual change in the unit volume of a liquid for 1K rise in its temperature. The real rate of volume expansion Br is always greater than the apparent rate of volume expansion Ba by an amount equal to the rate of volume expansion of the container Bg.
Thus,
Br=Ba+Bg where Br, Ba and Bg are represent Beta
It should be noted that different liquids have different coefficients of volume expansions.

Question # 3

Write a note on volume thermal expansion of solids

Ans 1: Volume thermal expansion; the volume of a solid also changes with the change in temperature and is called volume thermal expansion or cubical thermal expansion
Ans 2: Explanation: consider a solid of initial volume V_o at certain temperature T_o. On heating the solid to a temperature T, let its volume becomes V, then
change in the volume of solid=V-V_o
change in temperature= T-T_o

Question # 4

What is liquid-in-gas thermometer? explain it

Ans 1: Liquid-in-gas thermometer; a liquid-in-gas thermometer has a bulb with a long capillary tube of uniform a nd fine bore. A suitable liquid is filled in the bulb. When the bulb contacts a hot object, the liquid in it expands and rises in the tube. The glass stem of a thermometer is thick and acts as a cylindrical lens. This makes it easy to see the liquid level in the glass tube.
Mercury freezes at -39C and boils at 357C. It has all the thermometric properties listed above. Thus mercury is one of the most suitable thermometric material. mercury-in glass thermometers are widely used in laboratories, clinics and houses to measure temperature in the range from -10C to 150C
Ans 2: Lowe fixed points: the lower fixed point is marked to show the position of liquid in the thermometer when it is placed in ice.
Ans 3: Upper fixed points: upper fixed point is marked to show the position of liquid in the thermometer when it is placed in steam at standard pressure above boiling water.

Question # 5

Define specific heat capacity. Give the importance of large heat capacity of water

Ans 1:
Specific heat capacity: specific heat capacity of a substance is defined as the amount of heat required to raise the temperature of 1kg mass of the substance through 1K.
Unit: the SI unit of specific heat capacity is JKg^-1K^-1
Examples: specific heat capacity of water , ice and soil are 4200 Jkg^-1K^-1, 2100Jkg^-1k^-1 and 810JKg^-1K^-1 respectively
Ans 2: Importance of large heat capacity of water: specific heat capacity of water is large than dry soil. As a result , the temperature of soil would increase five times more than the same mas of water by the same amount of heat. Thus the temperature of land rises and falls more rapidly than that of sea. hence the temperature variations from summer to winter are much smaller at places near the sea than land for away from sea.
Water has a large specific heat capacity . For this reason, it is very useful in storing and caring thermal energy ue ti its high specific heat capacity. The cooling system of automobiles uses water to carry away unwanted thermal energy. In an automobile, large amount of heat is produced by its engine due to which its temperature goes on increasing. The engine would cease unless it is note cooled down. Water circulating around the engine maintains its temperature. Water absorbs unwanted thermal energy of the engine and dissipates heat through its radiator. in central heating system hot water is used to carry thermal energy through pipes from boiler to radiators. These radiators are fixed inside the house at suitable places.

Question # 6

Explain the change of state of matter

Ans 1: Change of state of matter: Matter can be changed from one state to another. For such a change to occur, thermal energy is added to or removed from a substance
Ans 2: Experiment: take a beaker and place it over a stand. put small piece of ice in the beaker and suspended a thermometer in the beaker to measure the temperature of ice.
Now place a burner under the beaker. The ice will start melting . The temperature of the mixture containing ice and water will not increase above 0C until all the ice melts and we get water at 0C. If this water 0c is further heated, its temperature will begin to increase above 0C.

Question # 7

What is bimetal strip ? explain and write its uses

Ans 1: Bimetal strip: a bimetal strip consists of two thin strips of different metals such as brass and iron joined together. On heating the strip , brass expands more than iron. This unequal expansion causes bending of strip.
Ans 2: Uses; bimetal strip are used for various purposes. bimetal thermometers are used to measure temperature especially in furnaces and ovens. Bimetal strips are also used in thermostats. Bimetal thermostat switch is used to control the temperature of heater coil in an electric iron.

Question # 8

Define latent heat of vaporization. explain it

Ans 1: Latent heat of vaporization: the quantity of heat that changes unit mass of a liquid completely into gas at its boiling point without any change in its temperature is caked latent heat of vaporization.
It is denoted by H_v.
When water is heated, it boils at 10C under standard pressure. its temperature remains 100C until it is changed completely into steam. Its latent heat of vaporization is 2.26*10⁶JKg^-1That is 1kg of water requires 2.26*10⁶J heat to change it completely into gases at its boiling point.
Ans 2: Experiment: take a beaker and place it over a stand. put small pieces of ice in the beaker and suspended a thermometer in the beaker to measure the temperature. Place a burner under the beaker. The ice will start melting. The temperature of the mixture containing ice and water will not increase above 0C until all the ice melts. Note the time which the ice take to melt completely into water at )C. Continue heating the water at 0C in the beaker. Its temperature will begin to increase. Note the time which the water in the beaker takes to reach its boiling point at 100C from 0C.
Continue heating water till all the water changes into steam. Note the time which the water in the beaker takes to change completely into steam at its boiling point 100C.

Question # 9

Explain the scales of temperature

Ans 1: Temperature scales: a scale is marked on thermometer. The temperature of the body in contact with the thermometer can be read on that scale.
Three scales of temperature are in common use. These are:
Ans 2: Celsius scale or centigrade scale: on Celsius scale, the interval between lower and upper fiexd points is divided into 100 equal parts. The lower fixed point is marked as 0C and upper fixed point is marked as 100C.
Ans 3: Fahrenheit scale: on Fahrenheit scale, the interval between lower and upper fixed points is divided into 180 equal parts. Its lower fixed point marked as 32F and upper fixed poin is marked as 212F
Ans 4: Kelvin scale: In SI unit of temperature is kelvin(K) and its scale is called kelvin scale of temperature. The interval between upper and lower fixed points is divided into 100 equal parts. thus, a change in 1C is equal to a change of 1 K. The lower fixed point on this scale corresponds to 273K and the upper fixed point is referred as 373K. The zero on this scale is called the absolute zero and is equal to -273C
Ans 5: From Celsius to kelvin scale; the temperature T on kelvin scale can be obtained by adding 273 in the temperature C on Celsius scale. Thus,
T(K)= 273+C
From kelvin to Celsius scale: the temperature on Celsius scale can be found by subtraction 273 from the temperature in kelvin scale. Thus,
C=T(K)-273
From Celsius to Fahrenheit scale: since 100 divisions on Celsius scale are equal to 180 divisions on Fahrenheit scale. Therefore, each division on Celsius scale is equal to 1.8 divisions on Fahrenheit scale. Moreover, 0C corresponds to 32 F
F= 1.8C+32

Question # 10

Explain the consequences and also application of thermal expansion.

Ans 1: Consequences of thermal expansions: the expansion of solids may damage the bridge, railway tracks and roads as they are constantly subjected to temperature changes. So provision is made during construction for expansion and contraction with temperature. For example, railway tracks bucked on a hot summer day due to expansion if gaps are not left between sections.
Bridge made of steel girders also expands during the day and contract during night. They will bend if their ends are fixed. to allow thermal expansions, one end is fixed while the other end of the girder rests on rollers in the gap left for expansion. Overhead transmission lines are also given a certain amount of sag so that they can contract in winter without snapping.
Ans 2: Application of thermal expansion: thermal expansion is used in our daily life. In thermometers, thermal expansion is used in temperature measurements. To open the cap of a bottle that is tight enough, immerse it in hot water for a minute or so. Metal cap expands and becomes loose. It would now be easy to turn it to open.
To join steel plates tightly together, red hot rivets are forced through holes in the plates. The end of hot rivet is then hammered. On cooling, the rivets contract and bring the plates tightly gripped. Iron rims are fixed on wooden wheels of carts. Iron rims are heated. Thermal expansion allows them to slip over wooden wheel. Water is poured on it to cool. The rim contracts and become tight over the wheel.

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Matric Part 1/9th Class Physics Chapter 8 Long Question With Answer for Unit 8 Thermal Properties of Matter

9th Class English Medium Subjects

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Online Long Questions For Chapter 8 "9th Class Physics Chapter 8 Long Question Preparation "

Physics (New Book) - 9th Class Physics Chapter 8 Long Question Preparation

Q no: 7 (B) Normal temperature of is 98.6 F. Convert it in the Celsius scale and .

Briefly explain thermal expansion of liquids

Write a note on volume thermal expansion of solids

What is liquid-in-gas thermometer? explain it

Define specific heat capacity. Give the importance of large heat capacity of water

Explain the change of state of matter

What is bimetal strip ? explain and write its uses

Define latent heat of vaporization. explain it

Explain the scales of temperature

Explain the consequences and also application of thermal expansion.

Prepare Complete Set Wise Questions For Chapter 8 "9th Class Physics Chapter 8 Long Question Preparation "

Set 1

Set 2

9th Class Physics Chapter 8 Long Question Preparation - Set 1

Q no: 7 (B) Normal temperature of is 98.6 F. Convert it in the Celsius scale and .

Briefly explain thermal expansion of liquids

Write a note on volume thermal expansion of solids

What is liquid-in-gas thermometer? explain it

Define specific heat capacity. Give the importance of large heat capacity of water

Explain the change of state of matter

What is bimetal strip ? explain and write its uses

Define latent heat of vaporization. explain it

Explain the scales of temperature

Explain the consequences and also application of thermal expansion.

9th Class Physics Chapter 8 Long Question Preparation - Set 2

Q no: 5 (B) How much heat is required to increase the temperature of 0.5 kg of water from 10°C to 65°C.?

Q no: 6(A) Explain land and Sea breeze are example of convection.?

What is bimetal strip ? explain and write its uses

Define specific heat capacity. Give the importance of large heat capacity of water

Define latent heat of fusion and explain it

Explain the change of state of matter

Explain the consequences and application of thermal expansion.

What is liquid-in-gas thermometer? explain it

Q no: 7 (B) Normal temperature of is 98.6 F. Convert it in the Celsius scale and .

Write a note on linear thermal expansion in solids

9th class Physics Chapter 8 Long Q's (English Medium)

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