1 4 UNDERSTANDING THERMAL EQUILIBRIUM · PDF file04/05/2012 · Physics Module Form 4 Chapter 4 - Heat GCKL 2010 4-1 4 4 UNDERSTANDING THERMAL EQUILIBRIUM What is thermal equilibrium

Physics Module Form 4 Chapter 4 - Heat GCKL 2010

4-1

4 UNDERSTANDING THERMAL EQUILIBRIUM

What is

thermal

equilibrium ?

1. (______, Temperature ) is a form of energy that flows from a hot body to a cold

body.

2. The SI unit for (______, temperature) is Joule, J.

3. ( Heat , _____________ ) is the degree of hotness of a body

4. The SI unit for (heat , ___________) is Kelvin, K.

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

bodies is (______, equal)

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

Two objects in thermal equilibrium have the …______ … temperature

irrespective of shape, mass, size or type of surface.

Calibration of

thermometer

7. The ______ ______ of an object is important in the construction of a

thermometer. It is a physical quantity which is sensitive to and changes linearly

with the change in temperature of the object.

4.1


4-2

8. ________________ (l 0 )/ ice point : the temperature of pure melting ice/00C

9. ________________ ( l 100)/steam point: the temperature of steam from water

that is boiling under standard atmospheric pressure /1000C

10. The lengths of the mercury column in the mercury-in-glass thermometer is 2.6 cm

at 0OC and 22.6 cm at 100

OC. When the thermometer is placed in hot water, the

length of the mercury column is 16.9 cm. Calculate the temperature of the hot

water.

Liquid-in-glass

thermometer

11. The liquid used in glass thermometer should

(a) Be easily ______

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

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

12. List the characteristic of mercury

(a) ______ liquid

(b) Does not ______ to the glass

(c) ______ uniformly when heated

(d) ______ point -390C

(e) ______ point 3570C

13. Which modification increases the sensitivity of the thermometer ?

A. Increasing the size of the bulb

B. Increasing the thickness of the bulb

C. Reducing the diameter of the capillary tube

D. Reducing the length of the capillary tube

Answer :


4-3

Check Yourself 1

1. The diagram below shows a thermometer is

used to measure the temperature of hot water.

When the thermometer and the hot water are in

thermal equilibrium, which of the following is

not correct ?

A. The temperature of hot water is equal to the

temperature of the thermometer

B. No heat flow between thermometer and hot

water

C. Heat flows from hot water to thermometer

D. Heat flows from thermometer to hot water

2. Which of the following characteristics does a

liquid-in-glass thermometer work ?

A. Volume of a fixed mass of liquid

B. Length of the liquid

C. Resistance of the liquid

D. Pressure of the liquid

3. Which of the following temperatures

corresponds to zero on the Kelvin scale ?

A. 273 O

C

B. 0 O

C

C. -273 O

C

D. 100 O

C

4. Diagram below shows the liquid levels from

the bulb in three thermometers P, Q and R at

certain temperatures.

What is the temperature reading at

thermometer R ?

A. 70.8 O

C

B. 65.4 O

C

C. 62.5 O

C

D. 57.7 O

C


4-4

4 UNDERSTANDING SPECIFIC HEAT CAPACITY

Definition of Heat Capacity

1. Quantity of ______ energy required to raise the temperature of an object by

10C.

2. The unit of heat capacity is ______

3. Beaker A has (greater, same, less) heat capacity than beaker B.

4. This means that the (bigger, smaller) the mass, the (larger, smaller) the

amount of heat stored.

Definition of Specific Heat

Capacity

1. Quantity of ______ energy required to raise the temperature of ______of a

substance by 10C.

2. The unit of specific heat capacity is ______

3. An object with low specific heat capacity can be heated up______, as it

requires less heat to increase its temperature by 10C. It can be cooled

______due to little amount of heat stored in it.

4. An object with high specific heat capacity takes ______ time to heat up, as it

requires more heat to increase its temperature by 10C. It is ______ to cool

down due to larger amount of heat stored in it.

Q = Pt

Pt = mc

Q = Heat supplied

P = Power of heater

T = Time in seconds

M = mass of substance

C = Specific heat capacity

= Increase in

temperature

4.2

A

A

B

A


4-5

Determining the heat capacity

of aluminium block

1. The purpose of wrapping the aluminium blok with wool ______ ______to or

______ of heat from the surrounding.

2. Oil in the holes for housing thermometer and the immersion heater is to

improve the ______ of heat from the heater to the thermometer through the

aluminium block.

3. The immersion heater of 50 W rated power is used for 5 minutes to heat up

the aluminium block. If the mass of the alumimium block is 1.0 kg and the

rise in temperature is 160C, what is the specific heat capacity of aluminium ?

15000937.5

1 16

PtC

m

Jkg-10C-1

4. Specific heat capacity calculated is usually ______ than the standard value

because some ______is lost to the surroundings.

Aim To investigate the relationship between temperature rise and mass of water

Experiment

Hypothesis When the mass of water …______ … the temperature rise will …______ ….

Manipulated variable ______ of water

Responding variable ______ in temperature

Fixed variable ______ duration, water, weighing scale, ______ rating of heater used

Apparatus Thermometer, water, beaker water, weighing scale

Setup

800C 600C 800C 400C


4-6

Procedure

1. 100 ml of water is placed in a 500 ml beaker.

2. A heater is placed in the water.

3. Heating process is carried out for 1minute.

4. Highest temperature achieved is recorded.

5. Step 2 to 4 is repeated for 200ml, 300ml, 400ml and 500ml of water.

Analysis

Volume of

water used,

V (ml)

Final

temperature,

T2 (

0C)

Initial

temperature,

T1 (

0C)

Rise in

temperature,

= T2 – T

1

(0C)

1/ (0C-1)

100

200

300

400

500

Conclusion

V

1/

Applications of specific heat capacity

Water as heating agent in

heating radiator


4-7

Water as a coolant in car

engine

Sea Breeze

(wind from the sea)

Land Breeze (wind from the

land)

2. Hot air rises up

from the land

1. During the day

land gets hotter

than the sea

because c land c sea

3. Cold water will be

recirculated to repeat

the process continously

1. Cool water is pumped into the hot

water reservoir to absorb a large amount

of heat due to its ______specific heat capacity.

1. Cool water is pumped

into the hot engine

3. Cool water is recirculated

through the engine blocks

and the process continues

while the engine is running

2. ______ specific heat

capacity of water allows it

to absorb a large amount

of ______from the

engine

2. hot air rises

from the sea

2. Heat from hot water is

released to the cooler

surroundings of a room to

achieve _____ _____

4. Hot water is

cooled by the

air from the

cooling fins

and the fan

3. Cool air

blows from

the sea to

replace the

space left by

the hot air

and

______ currents in

the air are formed

3. Cooler

air blows

from the

land to

replace the

space left

by the hot

air and

convection

currents in

the air are

formed.

1. During the

night, the sea

is hotter than

the land

because

c land c sea


4-8

Household apparatus and

utensils

Check Yourself 1

1. Table below shows four types of liquid with

their respective specific heat capacities and

boiling points. All the liquids have the same

mass and same temperatures of 30oC. If the

same amount of heat is supplied to them,

which liquid, A, B, C or D will boil first ?

Liquid Specific heat

capacity (Jkg-10C-1) Boiling point

(oC)

A 3.0 50

B 5.0 80

C 4.2 100

D 0.2 200

2. Table below shows the specific heat capacity

of four different metals.

Which of the following is the most suitable

metal to be used in a rice cooker for fast

heating ?

A. P

B. Q

C. R

D. S

3. Diagram below shows a bullet moving at a

velocity of 60 ms-1

is embedded in a wooden

block.

Assuming all the energy lost by the bullet is

converted to heat energy and is absorbed by

the bullet. What is the rise in temperature of

the bullet ? ( Specific heat capacity of the

bullet = 120 Jkg-10C-1)

A. 0.5 oC

B. 2.0 oC

C. 30.0 oC

D. 60.0 oC

4. Diagram below shows 200 g of water at 0 oC is

poured into a cup containing 400 g of water at

80 oC . Assuming there is no heat loss to the

surroundings.

What is the final temperature of the mixture ?

[ Specific heat capacity of water = 4200 Jkg-10

C-1]

A. 53 oC

B. 60 oC

C. 66 oC

D. 70 oC

Plastic handle _____specific heat capacity

Steel ______specific heat

capacity


4-9

5. Diagram below shows the temperature-time

graph of two solids X and Y of equal mass but

of different substances are heated

simultaneously by identical heaters.

Which of the following comparison is correct?

A. Cx > Cy

B. Cx < Cy

C. Cx = Cy


4-10

4 UNDERSTANDING SPECIFIC LATENT HEAT

Definition of

Latent Heat

1. Latent Heat is the total energy ________ or released when a substance changes

its ________ state completely at a ________ temperature.

2. Latent Heat of fusion is heat absorbed when ________ changes into ________ or

heat released when liquid changes into solid at constant________.

3. Latent Heat of vaporization is heat absorbed when ________ changes into

________or heat released when vapour changes into liquid at constant________.

4. Unit for latent heat is ________ .

5. Process in which solid directly changes into vapour is called ________ .

Definition of

Specific Latent

Heat

1. Specific Latent Heat of fusion is heat absorbed when 1 kg ________changes into

________or heat released when liquid changes into solid at constant________ .

2. Specific Latent Heat of vaporization is heat absorbed when 1 kg ________

changes into ________or heat released when vapour changes into liquid at

constant________ .

3. Unit for latent heat is________.

4. When temperature remain constant, ________energy of the molecules remain

constant. However energy absorbed is used to overcome ________ of attraction

and atmospheric pressure.

4.3


4-11

Heating curve Fill the empty boxes for the heating curve below with the following words

Calculation of

specific latent

heat of fusion

1. Calculate energy supplied by the heater.

2. What is the mass of ice melted due to the heat absorbed from the

surroundings?

3. Determine the specific latent heat of fusion of ice.

L = m

Pt=

3

(80)(3 60)

(49.2 6.4) 10

=

3

14400

42.8 10=

Solid, liquid, gas, boiling point, melting point,

latent heat of fusion, latent heat of vaporization

Mass of water collected in Set A = 49.2 g

Mass of water collected in Set B = 6.4 g

Power of heater = 80 W

Time interval of switching on the heater = 3 minutes


4-12

Check Yourself 1

1. Diagram below shows the cooling curve of a

Gas. Temperatures T1 and T2 represents

T1 T2

A. Solidification Room temperature

B. Boiling Point Solidification point

C. Melting Point Freezing Point

D. Melting Point Room temperature

2. Diagram below shows the heating curve of a

solid Y of mass 2 kg which is heated by a

heater of 70 W power. Which statement

below is NOT true ?

A. Specific latent heat of Y is 10500 Jkg-1

.

B. Specific heat capacity of solid Y and

liquid Y are the same

C. Total heat used is 1120 J

D. Melting point of Y is 10 oC

3. Diagram below shows the arrangement of

apparatus used to determine the specific latent

heat of vaporization of water. The water in the

beaker is heated by an immersion heater with a

power of 1 kW. The beaker and its content is

resting on an electronic balance which

measures the mass of the beaker and its

content.

When the water is boiling, it is found that 80 g

of water is boiled away in 3 minutes.

What is the specific latent heat of vaporization

of water ?

A. 2.10 x 106 Jkg

-1

B. 2.15 x 106 Jkg

-1

C. 2.20 x 106 Jkg

-1

D. 2.25 x 106 Jkg

-1

4. Diagram below shows the arrangement of

apparatus used to determine the specific latent

heat of fusion of ice. There are two identical

sets. One of the sets is called a control set

which is without a power supply.

The aim of the control set is


4-13

A. To find the mass of ice melted due to the

heat absorbed from the surroundings

B. To find the mass of water formed by

condensation from the vapour in the air

C. To detect any changes in the melting point

of the ice

D. To find the mass of water evaporated

5.

Heat produced in an engine block of car needs to be transferred out promptly to prevent overheating. This is

done by circulating a suitable cooling liquid through the engine block.

(a) What is meant by ‘specific heat capacity of water is 4200 Jkg-1o

C-1

?

________________________________________________________________________________

(b) Based on the table above,

(i) Explain the suitable characteristics of the cooling liquid to extract heat out of an engine block.

High Specific Heat Capacity

High specific latent heat of

vaporization

High boiling point

Low rusting rate

(ii) Decide which liquid is the most suitable and give reasons for your choice.

_____________________________________________________________________________

(c) Total energy released by an engine in 1 hour = 9.0 x 107 J

Energy breakdown : mechanical 40% and heat 60%

Mass of cooling liquid circulating in 1 hour = 150 kg

Temperature of water entering the engine = 30oC

Temperature of water exiting the engine = 60oC

Based on the information above,

(i) Calculate the power of the engine

(ii) Calculate the amount of heat produced by the engine in one hour.

(iii) Calculate the specific heat capacity of the cooling liquid.


4-14

(d) Suggest two ways to dissipate the heat from the cooling liquid.

1. ______________________________________________________________________________

2. ______________________________________________________________________________


4-15

4 UNDERSTANDING GAS LAWS

What is

kinetic theory

of gases ?

The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules),

all of which are in constant, _______ _______. The rapidly moving particles constantly collide with

each other and with the walls of the container. Kinetic theory explains ___________ properties of

gases, such as pressure, temperature, or volume, by considering their molecular composition and

motion.

The ___________ of an ideal __________ ____ is a measure of the average _______ _______ of its

atoms.

Define the

three gas

laws.

Boyles’ Law Charles’ Law Pressure Law

Formula

Condition T = ___________and

_______ of gas are

constant

P = ______ and

_____ of gas are constant

(temperature must be in

______scale)

V = ______ and

____ of gas are constant

(temperature must be in

______ scale)

Graphs

4.4

http://en.wikipedia.org/wiki/Atom

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Kinetic_energy


4-16

Experiment

al set up

Calculation

involving

Boyle’s Law.

Diagram on the right shows an arrangement to investigate the

relationship between pressure and volume of a fixed mass of gas

at constant temperature. The pressure of the air in the glass tube is

measured by a pressure gauge and the pressure can be

increased by using the bicycle pump. The pump of the gas is 1.5

x 105 Pa when the volume is 80 cm

3.

(a) Explain how a gas exerts a pressure on the walls of its container.

__________________________________________________________________________

__________________________________________________________________________

(b) State the Boyle’s law.

__________________________________________________________________________

__________________________________________________________________________

(c) Find the volume of the gas when pressure is 2.5 x 105 Pa

(d) Find the pressure of the gas when the volume of the gas is 60 cm3.

(e) A bubble of air rises from the bottom of a pond to the surface. As the bubble reaches the

surface, its volume is double its original volume. Assume the temperature is constant, find

the depth of the pond. [Atmospheric pressure = 10 m of water]


4-17

Question

involving

Charles’

Law.

(a) State Charles’ law.

__________________________________________________________________________

__________________________________________________________________________

(b) Diagrams below shows how (a) the pressure of the gas change with temperature and (b) the

volume of the gas change with temperature .

(a) (b)

(i) Compare the characteristics displayed by the graphs.

1. _______________________________________________________________

2. _______________________________________________________________

3. _______________________________________________________________

(ii) Relate the information you have mentioned to form a physics concept.

______________________________________________________________________

______________________________________________________________________

(iii) Name the concept.

______________________________________________________________________

(c) (i) Define pressure.

______________________________________________________________________

(iv) Using kinetic theory of gas, explain why the pressure of a gas in a fixed container

increases with an increase in its temperature.

1. _______________________________________________________________

2. _______________________________________________________________

3. _______________________________________________________________


4-18

Questions

involving

Pressure Law.

Diagram (a) shows the conditon of a snack pack kept in a refrigerator at 18oC, whereas Diagram (b)

shows the condition of the same snack pack in Borneo Highlands at the same temperature at 18oC.

(a) (b)

Based on the above information and observation,

(a) State one suitable inference.

______________________________________________________________________

(b) State one suitable hypothesis.

______________________________________________________________________

(c) With the use of appropriate apparatus, describe an experiment framework to test your

hypothesis. In your description, state clearly the following:

(i) Aim of the experiment

______________________________________________________________________

(ii) Variables used in the experiment

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

(iii) List of apparatus and materials

_________ pressure gauge, a _______ with volume scale, rubber tube and retort

stand.

(iv) Arrangement of the apparatus


4-19

(v) The procedure of the experiment which include the method of controlling the

manipulated variable and the method of measuring the responding variable

1. The apparatus for the experiment is set up as shown in the diagram

2. The ______ of the syringe is pressed down slowly until the volume of air inside

the syringe is 100 cm3

3. The ________ of the air in the syringe is read from the Bourdon gauge

4. The experiment is repeated with ________of air fixed at 80 cm3,

5. Make sure that there is no _____ and no increase in ___________ .

6.

(vi) The way you would tabulate the data

(vii) The way you would analyze the data

Volume, V (cm3) Pressure, P (Pa)

100.0

80.0

60.0

40.0

20.0

Check Yourself 1

1. Diagram below shows a valve P connecting

two cylinders, A dan B. When P is opened,

gas from cylinder A moves to cylinder B.

Which physical quantities does not change ?

A. Pressure

B. Volume

C. Mass

D. Density

2. The graph in the diagram

below shows the

relationship between

pressure, P and volume, V

of a fixed mass of gas at

constant temperature.

What is the value of V2 ?

A. 2.0 x 10 -4

m3

B. 4.0 x 10 -4

m3

C. 5.0 x 10 -4

m3

D. 8.0 x 10 -4

m3

3. Diagram below shows capillary tubes (a) and

(b) which are identical. If the atmospheric

pressure is 75 cmHg, determine the length of

gas column x and the pressure p.

Length Pressure

x (cm) p (cmHg)

P


4-20

A. 24.0 70

B. 21.0 75

C. 22.4 80

D. 21.0 70

4. Diagram below shows a fan is allowed to blow

in a closed room for an hour. What are the

possible changes to the pressure and

temperature of the air in the room ?

Temperature Pressure

A. Increases no change

B. No change increases

C. Decreases increases

D. Increases Increases

5. Air at a temperature of 27oC is kept in a

container at a pressure of 1 atmosphere. What

is the pressure of the air, in atmosphere, if it is

heated to a temperature of 77oC ?

A. 0.35

B. 0.86

C. 1.17

D. 2.85

6. Table below shows the volume and

temperature of a fixed mass of gas kept at

constant pressure.

V (cm3) 50 100

T(oC) 27 x

What is the value of x ?

A. 54 oC

B. 300 oC

C. 327 oC

D. 600 oC

Documents

1 4 UNDERSTANDING THERMAL EQUILIBRIUM · PDF file04/05/2012 · Physics Module Form 4 Chapter 4 - Heat GCKL 2010 4-1 4 4 UNDERSTANDING THERMAL EQUILIBRIUM What is thermal equilibrium