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Physics Module Form 4 Chapter 4 - Heat GCKL 2010

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4.14 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.

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 100OC. 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.

Answer :

Liquid-in-glass thermometer

11. The liquid used in glass thermometer should

(a) Be easily

(b) Exp an d a n d c o n t r a c t ra p id l y o v e r a r a n g e o f te m p e ra t u r e

(c) N o t to t h e gl a ss w a l l o f t h e c ap i l la r y t u b e

12. List the characteristic of mercury

(a) l i q u i d

(b) Does not t o t h e g la ss

(c) u n i f o r m l y w h en h e a ted

(d) p o i n t - 3 9 0 C

(e) p o i n t 35 7 0 C

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

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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 isnot 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 OC

B. 0 OC

C. -273 OC

D. 100 OC

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 OC

B. 65.4 OC

C. 62.5 OC

D. 57.7 OC

Physics Module Form 4 Chapter 4 - Heat GCKL 2011

4.24 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.

A B

4. This means that the (bigger, smaller) the mass, the (larger, smaller) the amount of heat stored.

Definition of Specific HeatCapacity

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 l ow s p ec i f i c heat ca p ac i t y can be heated up , as it

r eq u ir e s l e s s he a t to increase its temperature by 10C. It can be cooled due to l i t tl e a m ount of h e at s t o r ed in it.

4. An object with h i g h sp e c i f i c he a t c a pa c it y takes time to heat up, as it

r eq u ir e s m o r e he a t to increase its temperature by 10C. It is to cool down due to l a r g er a m ount of h e at s t o r ed in it.

Q = PtPt = mcQ = Heat suppliedP = Power of heaterT = Time in secondsM = mass of substanceC = Specific heat capacity = Increase in

temperature

Determining the heat capacity of aluminium block

1. The purpose of wrapping the aluminium blok with wool to or o f he a t 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 therise in temperature is 16

0C, what is the specific heat capacity of aluminium ?

C Pt m

15000 937.5 Jkg-10C-1

116

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

800C 60

0C 800C 400C

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

Manipulated variable o f w a t er

Responding variable i n t e m p er a t ure

Fixed variable d u ra t i on, w a t e r , w e i ghi n g s c a l e , ra t i ng o f he a t e r us e d

Apparatus Thermometer, water, beaker water, weighing scale

Setup

Physics Module Form 4 Chapter 4 - Heat GCKL 2011

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.

AnalysisVolume ofwater used,

V (ml)

Finaltemperature,

T2 (0C)

Initialtemperature,

T1 (0C)

Rise intemperature,

= T2 – T1

(0C)

1/ (0C-1)

100

200

300

400

500

ConclusionV

1/

Applications of specific heat capacity

Wa t er a s h e a t i ng a g ent i n hea t i ng r a d i a t or

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Physics Module Form 4 Chapter 4 - Heat GCKL 2011

2. Heat from hot water is released to the cooler surroundings of a room to

achieve

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

Wa t er a s a coo l ant i n car en g i ne

4. Hot water is cooled by the air from the cooling finsand the fan 2. specific heat

capacity of water allows it to absorb a large amount

of from the

3. Cool water is recirculatedthrough the engine blocks 1. Cool water is pumped

and the process continues into the hot engine

while the engine is running

Sea Br e e z e

( w i nd fr om t he s e a )

3. Cool air2. Hot air rises up blows from from the land the sea to

replace the space left by

1. During the day the hot air land gets hotter andthan the seabecause c land c sea currents in

the air are formed

Land B r e e z e ( w i nd f r om t he l an d )

3. Cooler air blowsfrom the 2. hot air rises land to from the sea replace thespace leftby the hot

1. During the air and

night, the sea convection

is hotter than currents in

the landthe air are

because formed.c land c sea

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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

Physics Module Form 4 Chapter 4 - Heat GCKL 2011

Plastic handle specific heat capacity

H ous e h o l d ap p a r a t u s a nd u t en s i l s

Steel specific heat

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 ?

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 oCoC. 30.0 C

2. Table below shows the specific heat capacity of four different metals.

D. 60.0 oC

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

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

poured into a cup containing 400 g of water at80 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-10C-1]

A. 53 oC

B. 60 oC

C. 66 oC

D. 70 oC

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

4.34 UNDERSTANDING SPECIFIC LATENT HEAT

Definition ofLatent Heat

1. Latent Heat is the total energy or released when a substance changesits state completely at a temperature.

2. La t e n t H e a t o f f u s i on is heat absorbed when changes into or heat released when liquid changes into solid at constant .

3. La t e n t H e a t o f v apo ri za ti on 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. Spec i f i c L a t e n t H e a t of f u s i on is heat absorbed when 1 kg changes into or heat released when liquid changes into solid at constant .

2. Spec i f i c L a t e n t H e a t of v a p o ri z a t i on is heat absorbed when 1 k g 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.

Physics Module Form 4 Chapter 4 - Heat GCKL 2011

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

Solid, liquid, gas, boiling point, melting point, latent heat of fusion, latent heat of vaporization

Calculation of specific latent heat of fusion

Mass of water collected in Set A = 49.2 g Mass of water collected in Set B = 6.4 g Power of heater = 80 WTime interval of switching on the heater = 3 minutes

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.

Pt (80)(3 60) 14400

L = = = =m (49.2 6.4) 103 42.8 103

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Physics Module Form 4 Chapter 4 - Heat GCKL 2011

Check Yourself 1

1. Diagram below shows the cooling curve of aGas. Temperatures T1 and T2 represents

T1 T2

A.

B.

C.

D.

Solidification

Boiling Point

Melting Point

Melting Point

Room temperature

Solidification point

Freezing 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 andliquid 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

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-1oC-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 ofvaporization

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.

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

1.

2.

4.44 UNDERSTANDING GAS LAWS

What is kinetic theory

of gases ?

The kin e t i c t h eory of gases describes a gas as a large number of small particles (a t o m s or m o l ec u l e s ) , 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.

B o y l e s ’ Law C harl e s ’ Law P r e s s u re 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

Physics Module Form 4 Chapter 4 - Heat GCKL 2011

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 beincreased by using the bicycle pump. The pump of the gas is 1.5 x 105 Pa when the volume is 80 cm3.

(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]

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Physics Module Form 4 Chapter 4 - Heat GCKL 2011

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.

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

p r e s s u r e g au g e, a wi t h v o l u m e s c a l e, r ub b er t ube and r e t o r t s t an d .

(iv) Arrangement of the apparatus

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

100.0

80.0

60.0

40.0

20.0

(v) The procedure of the experiment which include the method of controlling the manipulated variable and the method of measuring the responding variable

1. T he ap p a r a t us f or t h e ex p e r i m ent i s s e t up a s s ho w n i n t he d i a g r am 2. T he of t he s y ri n g e i s p r e s s ed do w n s l o w l y un t i l t h e v o l u m e of a i r i n s i de

t he s yr i n g e i s 1 00 c m 3 3. T he o f t h e a i r i n t he s yr i n g e i s r e a d f r om t he Bourd o n g au g e

4. T he ex p e r i m ent i s r ep e a t ed w it h of a i r f i xed a t 80 c m 3 , 5. M a k e s u r e t h at t h e r e i s no and no i nc r ea s e i n .6.

(vi) The way you would tabulate the data

(vii) The way you would analyze the data

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.

P

Which physical quantities does not change ?

A. PressureB. VolumeC. MassD. 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)

Physics Module Form 4 Chapter 4 - Heat GCKL 2010

A. 24.0 70B. 21.0 75C. 22.4 80D. 21.0 70

Temperature Pressure

A. B. C. D.

Increases No change Decreases Increases

no change increases increases Increases

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 ?

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. 0.35B. 0.86C. 1.17D. 2.85

6. Table below shows the volume and temperature of a fixed mass of gas kept at constant pressure.

V (cm3) 50 100T(oC) 27 x

What is the value of x ?

A. 54 oCoB. 300 C

C. 327 oC

D. 600 oC