chapter 4heat student's copy

8/14/2019 Chapter 4heat Student's Copy

1/34

JPN Pahang Physics Module Form 4Students Copy Chapter 4: Heat

4.1 : UNDERSTANDING THERMAL EQUILIBRIUM

By the end of this subtopic, you will be able to

Explain thermal equilibrium

Explain how a liquid-in glass thermometer works

1. The net heat will flow from A to B until the temperature of A is the ( same, zero as the

temperature of B. In this situation, the two bodies are said to have reached thermal

equilibrium.

2. When thermal equilibrium is reached, the net rate of heat flow between the two bodies is

(zero, equal)

3. There is no net flow of heat between two objects that are in thermal equilibrium. Two objects

in thermal equilibrium have the temperature.

4. The liquid used in glass thermometer should

(a) Be easily seen

(b) Expand and contract rapidly over a wide range of temperature

(c) Not stick to the glass wall of the capillary tube

5. List the characteristic of mercury

(a) Opaque liquid

(b) Does not stick to the glass

(c) Expands uniformly when heated

(d) Freezing point -390C

(e) Boiling point 3570C

1

Thermal equilibrium:Keseimbangan terma

CHAPTER 4: HEAT

..

.

..

..

.

.

.

.

.. rate of energy transfer

Hot

object

Cold

object

.. rate of energy transfer

Equivalent to Equivalent to

No net heat transfer

A B


2/34


6. ( Heat, Temperature ) is a form of energy. It flows from a hot body to a cold body.

7. The SI unit for( heat , temperature) is Joule, J.

8. ( Heat , Temperature ) is the degree of hotness of a body

9. The SI unit for (heat , temperature) is Kelvin, K.

10. Lower fixed point (l0 )/ ice point : the temperature of pure melting ice/00C

11. Upper fixed point( l 100)/steam point: the temperature of steam from water that is boiling

under standard atmospheric pressure /1000C

Exercise 4.1

Section A: Choose the best answer

1. The figure shows two metal blocks.

Which the following statement is false?

A. P and Q are in thermal contact

B. P and Q are in thermal equilibriumC. Energy is transferred from P to Q

D. Energy is transferred from Q to P

2. When does the energy go when a cup of

hot tea cools?

A. It warms the surroundings

B. It warms the water of the tea

C. It turns into heat energy anddisappears.

3. Which of the following temperature

corresponds to zero on the Kelvin scale?A. 2730 C

B. 00C

C. -2730 CD. 1000 C

4. How can the sensitivity of a liquid- in glass thermometer be increased?

A. Using a liquid which is a better

conductor of heat

2

..

l0

: length of mercury at ice point

l100

: length of mercury at steam point

Temperature, =l

- l0

l

x 1000C


3/34


B. Using a capillary tube with anarrower bore.

C. Using a longer capillary tubeD. Using a thinner-walked bulb

5. Which instrument is most suitable formeasuring a rapidly changing

temperature?

A. Alcohol-in glass thermometerB. Thermocouple

C. Mercury-in-glass thermometer

D. Platinum resistance thermometer

6. When shaking hands with Anwar, Kent

Hui niticed that Anwars hand was cold.However, Anwar felt that Kent Hui hand

was warm. Why did Anwar and Kent

Hui not feel the same sensation?A. Both hands in contact are in

thermal equilibrium.B. Heat is flowing from Kent Huis

hand to Anawrs hand

C. Heat is following from Anwars

hand to Kent Hui hand.

Section B: Answer all the questions by showing the calculation

1. The length of the mercury column at the ice point and steam point are 5.0 cm and 40.0cmrespectively. When the thermometer is immersed in the liquid P, the length of the mercury

column is 23.0 cm. What is the temperature of the liquid P?

2. The length of the mercury column at the steam point and ice point and are 65.0 cm

and 5.0cm respectively. When the thermometer is immersed in the liquid Q, the length of the

mercury column is 27.0 cm. What is the temperature of the liquid Q?

Temperature, = l l0 x 1000C

l100 l0

= 27 5 x 1000C

65 - 5

= 36.670C

3


4/34


3. The distance between 00C and 1000C is 28.0 cm. When the thermometer is put into a beaker

of water, the length of mercury column is 24.5cm above the lower fixed point. What is the

temperature of the water?

4. The distance between 00C and 1000C is 25 cm. When the thermometer is put into a beaker of

water, the length of mercury column is 16cm above the lower fixed point. What is the

temperature of the water? What is the length of mercury column from the bulb at

temperatures i) 300C

4


5/34


SECTION C: Structured Questions

1. Luqman uses an aluminium can, a drinking straw and some plasticine to make a simple

thermometer as shown in figure below. He pours a liquid with linear expansion into the can.

(a) Suggest a kind of liquid that expands linearly. (1m)

.

(b) He chooses two fixed points of Celsius scale to calibrate his thermometer. State them

(2m)

(c) If the measurement length of the liquid inside the straw at the temperature of the lower

fixed point and the upper fixed point are 5cm and 16 cm respectively, find the length of

the liquid at 82.50C.

(d) Why should he use a drinking straw of small diameter?

(e) What kind of action should he take if he wants to increase the sensitivity of his

thermometer?

5


6/34


2. What do you mean by heat and temperature?

....

4.2 : UNDERSTANDING SPECIFIC HEAT CAPACITY

By the end of this subtopic, you will be able to

Define specific heat capacity

State that c = Q/MC

Determine the specific heat capacity of a liquid

Determine the specific heat capacity of a solid

Describe applications of specific heat capacity

Solve problems involving specific heat capacity

1. The .. of a body is the .. that must be supplied to the body

to increase its temperature by 10C.

2. The heat capacity of an object depends on the

(a) .

(b) .

(c)

3. The of a substance is the amount of heat that must be supplied to

increase the temperature by 1 0C for a mass of 1 kg of the substance. UnitJkg-1K-1

4. The heat energy absorbed or given out by an object is given by Q = mcO.

6

Heat capacityMuatan haba

Specific heat capacityMuatan haba tentu

Specific heat capacity , c =Q__


7/34


5. High specific heat capacity absorb a large amount of heat with only a

temperature increase such as plastics.

6. Conversion of energy

7. Applications of Specific Heat Capacity

Explain the meaning of above application of specific heat capacity:

(a) Water as a coolant in a car engine

(i) ...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

7

Electrical energy Heat energy

Pt = mc

Heater

Power = Penergy

..energy

..energy

Object falls from

A hi h osition

Moving object stopped

due to friction

Heat energy

m h= mc

Heat energy

mv2= mc

Small value of c Big value of cTwo object of

equal mass

Equal rate ofheat supplied

.

increase intem erature

.

increase intem erature


8/34


...................................................................................................................................

...................................................................................................................................

.....

(b) Household apparatus and utensils

...

...

...

...

(c) Sea breeze

(d) Land breeze

8


9/34


Exercise 4.2

SECTION A : Choose the best answer

1. The change in the temperature of an

object does not depend onA. the mass of the object

B. the type of substance the object ismade of

C. the shape of the object

D. the quantity of heat received

2. Which of the following defines thespecific heat capacity of a substance

correctly?

A. The amount of heat energy requiredto raise the temperature of 1kg of the

substance

B. The amount of heat energy requiredto raise 1kg of the substance by 10C.

C. The amount of heat energy required

to change 1kg of the substance from

the solid state to the liquid state.

3. Heat energy is supplied at the same rate

to 250g of water and 250g of ethanol.The temperature of the ethanol rises

faster. This is because the ethanol..A. is denser than water

B. is less dense than water

C. has a larger specific heat capacity

than waterD. has a smaller specific heat capacity

than water

4. In the experiment to determine the

specific heat capacity of a metal block,

some oil is poured into the holecontaining thermometer. Why is this

done?

A. To ensure a better conduction of heatB. To reduce the consumption of

electrical energy

C. To ensure the thermometer is in an

upright position.D. To reduce the friction between the

thermometer and the wall of the

block.

SECTION B: Answer all questions by showing the calculation

9


10/34


1. How much heat energy is required to raise the temperature of a 4kg iron bar from 320C to

520C? (Specific heat capacity of iron = 452 Jkg-1 0C-1).

2. Calculate the amount of heat required to raise the temperature of 0.8 kg of copper from 350C

to 600C. (Specific heat capacity of copper = 400 J kg -1 C-1).

3. Calculate the amount of heat required to raise the temperature of 2.5 kg of water from 320C

to 820C. (Specific heat capacity of water = 4200 J kg -1 C-1).

4. 750g block of a aluminium at 1200C is cooled until 450C. Find the amount of heat is

released. . (Specific heat capacity of aluminium = 900 J kg -1 C-1).

5. 0.2 kg of water at 700C is mixed with 0.6 kg of water at 300C. Assuming that no heat is lost,

find the final temperature of the mixture. (Specific heat capacity of water = 4200 J kg-1 C-1)

10


11/34


SECTION C: Structured questions

1. In figure below, block A of mass 5kg at temperature 1000C is in contact with another block B

of mass 2.25kg at temperature 200C.

Assume that there is no energy loss to the surroundings.

(a) Find the final temperature of A and B if they are in thermal equilibrium. Given the

specific heat capacity of A and B are 900 Jkg-1 C-1 and 400 Jkg-1 C-1 respectively.

(b) Find the energy given by A during the process.

(c) Suggest one method to reduce the energy loss to the surroundings.

..

11

AB

1000C 200C

5kg

2.25kg


12/34


4.3 UNDERSTANDING SPECIFIC LATENT HEAT

By the of this subtopic, you will be able to

State that transfer of heat during a change of phase does not cause a change in temperature

Define specific latent heat

State that l = Q/m

Determine the specific latent heat of fusion and specific latent heat of vaporisation

Solve problem involving specific latent heat.

1. Four main changes of phase.

2. The heat absorbed or the heat released at constant temperature during a change of

phase is known as latent heat. Q= ml

3. Complete the diagrams below and summarized.

(a) Melting

12

SolidSolidification

Latent heat

Boiling

Latent heat . Condensation

Latent heat

Li uid

Gas


13/34


(b) Boiling

(c) Solidification

(d) Condensation

13

Tem erature

Time

.

Tem erature

Time

.

Tem erature

Time

.

Tem erature

Time

.


14/34


4. is the heat absorbed by a melting solid. The specific latent

heat of fusion is the quantity of the heat needed to change 1kg of solid to a liquid at its

melting point without any increase in .. The S.I unit of the specific

latent heat of fusion is Jkg-1.

5. ... is heat of vaporisation is heat absorbed during boiling.

The specific latent heat of vaporisation is the quantity of heat needed to change 1kg ofliquid

into gas or vapour of its boiling point without any change in .. The S.I

unit is Jkg-1.

14

waterice

watergas


15/34


6. Explain the application of Specific Latent Heat above:

:

(d) Cooling of beverage

(e) Preservation of Food

15


16/34


(f) Steaming Food

(g) Killing of Germs and Bacteria

EXERCISE 4.3

Section A:

1. The graph in figure below shows how

the temperature of some wax changes asit cools from liquid to solid. Which

section of the graph would the wax be a

mixture of solid and liquid?

16


17/34


A. PQ

B. QR C. RS

D. ST

2. Figure show a joulemeter used formeasuring the electrical energy to melt

some ice in an experiment. To find the

specific latent heat of fusion of ice, what

must be measured?

A. The time taken for the ice to meltB. The voltage of the electricity supply

C. The mass of water produced by

melting iceD. The temperature change of the ice.

3. It is possible to cook food much faster

with a pressure cooker as shown above.

Why is it easier to cook food using apressure cooker?

A. More heat energy can be supplied to

the pressure cooker

B. Heat loss from the pressure cookercan be reduced.

C. Boiling point of water in the pressure

cooker is raisedD. Food absorbs more heat energy from

the high pressure steam

4. Which of the following is not a

characteristics of water that makes it

widely used as a cooling agent?

A. Water is readily availableB. Water does not react with many other

substanceC. Water has a large specific heat

capacity

D. Water has a large density

5. Figure below shows the experiment set

up to determine the specific latent heat

of fusion of ice. A control of theexperiment is set up as shown in Figure

(a) with the aim of

17


18/34


A. determining the rate of melting of ice

B. ensuring that the ice does not melttoo fast.

C. determining the average value of the

specific latent heat of fusion of ice.

D. determining the mass of ice thatmelts as a result of heat from the

surroundings

6. Scalding of the skin by boiling water is

less serious then by steam. This isbecause

A. the boiling point of water is less than

the temperature of steamB. the heat of boiling water is quickly

lost to the surroundings

C. steam has a high specific latent heat.

D. Steam has a high specific heatcapacity.

SECTION B: Answer the question by showing the calculation

1. 300g of ice at 00C melts. How much energy is required for this

Question 2-7 are based on the following information

Specific heat capacity of water = 4 200 J kg-1 C-1

Specific heat capacity of ice = 2 100 J kg-1 C-1

Specific latent heat of fusion of ice = 3.34 X 105J kg-1

Specific latent heat of vaporization of water = 2.26 X 106 J kg-1

2. An immersion heater rated at 500 W is fitted into a large block of ice at 00C. How long does

it take to melt 1.5kg of ice?

3. 300 g of water at 400C is mixed with x g of water at 800C. The final temperature of the

mixture is 700C. Find the value of x

18


19/34


4. Calculate the amount of heat released when 2 kg of ice at 00C is changed into water at 00C.

5. Calculate the amount of heat needed to convert 3 kg of ice at 00C to water at 300C.

6. Find the amount of heat needed to convert 0.5 kg of ice at 150C into steam at 1000C

7. Calculate the amount of heat needed to convert 100 g of ice at 00C into steam at 1000C.

8. The specific latent heat of vaporization of water is 2300 kJ kg-1. How much heat will be

absorbed when 3.2 kg of water is boiled off at its boiling point.

4.4 UNDERSTANDING THE GAS LAW

By the end of this subtopic; you will be able to :

Explain gas pressure, temperature and volume in terms of the behaviour of gas molecules.

Determine the relationship between

19


20/34


(i) pressure and volume

(ii) volume and temperature

(iii) pressure and temperature

Explain absolute zero and the absolute/Kelvin scale of temperature

Solve problems involving pressure, temperature and volume of a fixed mass of gas

1. Complete the table below.

Property of gas ExplanationVolume,V

m3

Temperature,T

K (Kelvin)

Pressure,P

Pa(Pascal)

2. The kinetic theory of gas is based on the following assumptions:

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

....

4.4.1 Boyles Law

20

Small volume

molecules hit wall

more often, greater

pressure

P 1

V

That is PV = constant

Or P V = P V

Relationshi between ressure and volume


21/34


1. Boyles law states that...

............................................................................

2. Boyles law can be shown graphically as in Figure above

3. The volume of an air bubble at the base of a sea of 50 m deep is 250cm3. If the atmospheric

pressure is 10m of water, find the volume of the air bubble when it reaches the surface of the

sea.

21

P

V

(a) P inversely proportional to V

P

1/V

(b) P directly proportional to 1/V

PI=50m + 10m

V1=250cm3

P2= 10m


22/34


4.4.2 Charless Law

1. Charles law states .

The temperature -2730C is the lowest possible temperature and is known as the absolutezero of

temperature.

2. Fill the table below.

Temperature Celsius scale (0C) Kelvin Scale(K)

Absolute zero

Ice point

Steam point

22

Relationship between

volume and temperature

Lower temperature

Higher temperature,

faster molecules,

larger volume to keep

the pressure constant

V T

that is V = constant

T


23/34


Unknown point

3. Complete the diagram below.

4.4.3 Pressures Law

1. The pressure law states ....

..

EXERSICE 4.4:Gas Law

1. A mixture of air and petrol vapour is injected into the cylinder of a car engine when the

cylinder volume is 100 cm3. Its pressure is then 1.0 atm. The valve closes and the mixture is

compressed to 20 cm3. Find the pressure now.

23

/0C100-273

P T

That is P = constant T

Relationship between pressure

and temperature

Higher temperature

molecules move

faster, greater

pressure


24/34


2. The volume of an air bubble at the base of a sea of 50 in deep is 200 cm3. If the atmospheric

pressure is 10 in of water, find the volume of the air bubble when it reaches the surface of

the sea.

3. The volume of an air bubble is 5 mm3 when it is at a depth of h in below the water surface.

Given that its volume is 15 mm3 when it is at a depth of 2 in, find the value of h.

(Atmospheric pressure = 10 m of water)

4. An air bubble has a volume of V cm3 when it is released at a depth of 45m from the water

surface. Find its volume (V) when it reaches the water surface. (Atmospheric pressure = 10

m of water)

24


25/34


5. A gas of volume 20m3 at 370C is heated until its temperature becomes 870C at constant

pressure. What is the increase in volume?

6. The air pressure in a container at 330C is 1.4 X 1O5 N m2. The container is heated until the

temperature is 550C. What is the final air pressure if the volume of the container is fixed?

7. The volume of a gas is 1 cm3 at 150C. The gas is heated at fixed pressure until the volume

becomes triple the initial volume. Calculate the final temperature of the gas.

8. An enclosed container contains a fixed mass of gas at 250C and at the atmospheric pressure.

The container is heated and temperature of the gas increases to 980C. Find the new pressure

of the gas if the volume of the container is constant.(Atmospheric pressure = 1.0 X 105N

rn2)

25


26/34


9. The pressure of a gas decreases from 1.2 x 105 Pa to 9 x 105 Pa at 400C. If the volume of the

gas is constant, find the initial temperature of the gas.

PART A: CHAPTER 4

1. A 5kg iron sphere of temperature 500C is

put in contact with a 1kg copper sphereof temperature 273K and they are put

inside an insulated box. Which of the

following statements is correct whenthey reach thermal equilibrium?

D. A iron sphere will have a

temperature of 273K

E. The copper sphere will have a

temperature of 500

C.F. Both the sphere have the same

temperature.

G. The temperature of the ironsphere will be lower than 500C

2. In the process to transfer heat from oneobject to another object, which of the

26


27/34


following processes does not involve a

transfer to material?

A. ConvectionB. Vaporisation

C. Radiation

D. Evaporation

3. When we use a microwave oven to heat

up some food in a lunch box, we shouldopen the lid slightly. Which of the

following explanations is correct?

A. To allow microwave to go inside

the lunch boxB. To allow the water vapors to go

out, otherwise the box will

explode

C. To allow microwave to reflectmore times inside the lunch box

D. To allow microwave to penetratedeeper into the lunch box.

4. Water is generally used to put out fire.

Which of the following explanation is

not correct?

A. Water has a high specific heat

capacityB. Steam can cut off the supply of

oxygen

C. Water is easily availableD. Water can react with some

material

5. Given that the heat capacity of a certainsample is 5000 J0C-1. Which of the

following is correct?

A. The mass of this sample is 1kg.B. The energy needed to increase

the temperature of 1 kg of this

sample is 5000 J.C. The energy needed to increase

the temperature of 0.5kg of this

sample is 2500J.

D. The temperature of this sample

will increase 10C when 5 000 J

energy is absorbed by thissample.

6. Which of the following statement iscorrect?

A. The total mass of the object is

kept constant when fusionoccurs.

B. The internal energy of the object

is increased when condensation

occursC. Energy is absorbed when

condensation occurs.

D. Energy is absorbed when

vaporization occurs.

7. Water molecules change their statesbetween the liquid and gaseous states

A. only when water vapour is

saturatedB. at all times because evaporation

and condensation occur any time

C. only when the vapour moleculesproduce a pressure as the same as

the atmospheric pressure

D. only when the water is boiling

8. Based on the kinetic theory of gas which

one of the following does not explain the

behaviour of gas molecules in acontainer?

A. Gas molecules move randomly

B. Gas molecules collide elasticallywith the walls of the container

C. Gas molecules move faster as

temperature increasesD. Gas molecules collide

inelastically with each other

27


28/34


9. A cylinder which contains gas is

compressed at constant temperature of

the gas increase becauseA. the average speed of gas

molecules increases

B. the number of gas moleculesincreases

C. the average distance between the

gas molecules increasesD. the rate of collision between the

gas molecules and the walls

increases

10. A plastic bag is filled with air. It is

immersed in the boiling water as shown

in diagram below.

Which of the following statements isfalse?

A. The volume of the plastic bag

increases.B. The pressure of air molecules

increases

C. The air molecules in the bag

move fasterD. The repulsive force of boiling

water slows down the movement

of air molecule

PART B;

1. A research student wishes to carry out an investigation on the temperature change of the

substance in the temperature range -500C to 500C. The instrument used to measure the

temperature is a liquid in glass thermometer.

28


29/34


Table 1

(a) (i) State the principle used in a liquid- in glass thermometer.(1m)

........................................................................................................................................

(ii) Briefly explain the principle stated in (a)(i) (3m)

.

.

.

(b) Table 1 shows the characteristic of 4 types of thermometer: A,B C and D. On the basis

of the information given in Table 1, explain the characteristics of, and suggest a suitable

thermometer for the experiment.(5 m)

Thermometer A B C D

Liquid Mercury Mercury Alcohol Alcohol

Freezing point of liquid (0C) -39 -39 -112 -112

Boiling point of liquid (0C) 360 360 360 360

Diameter of capillary tube Large Small Large Small

Cross section

29


30/34


..

(c) The length of the mercury column in uncalibrated thermometer is 6.0cm and 18.5 cm at

00C and 1000C. respectively. When the thermometer is placed in a liquid, the length of

the mercury column is 14.0cm

(i) Calculate the temperature of the liquid

(ii) State two thermometric properties which can be used to calibrate a thermometer. (6m)

2. A metal block P of mass 500 g is heated is boiling water at a temperature of 1000C. Block P

is then transferred into the water at a temperature of 300C in a polystyrene cup. The mass of

water in the polystyrene cup is 250 g. After 2 minutes, the water temperature rises to 420C.

Assuming that the heat absorbed by the polystyrene cup and heat loss to the

surroundings are negligible.{Specific heat capacity of water 4 200 j kg -1 C-1)

Calculate

(a) the quantity of heat gained by water the polystyrene cup

30

Figure 2


31/34


32/34


(c) Calculate the time taken by the lead shot to fall from the top to the bottom of the tube.

(d) After inverting the tube 100 times, the temperature of the lead shot is found to have

increased by 30C.

i. Calculate the work done on the lead shot.

ii. Calculate the specific heat capacity of lead.

iii. State the assumption used in your calculation in (d)ii.

...

.

PART C: EXPERIMENT

1. Before travelling on a long journey, Luqman measured the air pressure the tyre of his car as

shown in Figure (a) He found that the air pressure of the tyre was 200 kPa. After the journey,

Luqman measured again the air pressure of the tyre as shown in Figure (b) He found that the

air pressure had increase to 245 kPa. Luqman also found that the tyre was hotter after the

journey although the size of the tyre did not change.

Using the information provided by Luqman and his observations on air pressure in the

tyre of his car:

32

Figure (a) Figure (b)


33/34


Choose suitable apparatus

such as pressure gauge, a

round-bottomed flask and

any other apparatus that may he necessary. In your description, state clearly the

following:

i. Aim of the experiment,

ii. Variables in the experiment,

iii. List of apparatus and materials,

iv. Arrangement of the apparatus,

v. The procedure of the experiment including the method of controlling the

manipulated variable and the method of measuring the responding variable,

vi. The way you would tabulate the data,

vii. The way you would analyse the data. [10 marks]

33

(a) State one suitable inference that can be

made. [1 mark]

(b) State appropriate hypothesis for an

investigation. [1 mark]

(c) Design an experiment to investigate the

hypothesis stated in (b).


34/34


chapter 4heat student's copy

Documents