4.1 Thermal Equilibrium

MODUL PDP SPM
PASCA PKP
NEGERI PERAK
2020

PHYSICS Form 4

4.1:
Thermal
Equilibrium

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4.1 Thermal Equilibrium

Learning Standard:

Pupils are able to:

• explain with examples thermal equilibrium in daily life.

• calibrate a liquid-in-glass thermometer using two fixed points.

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4.1 notE

1. Diagram 1 shows two objects (soup and metal spoon) are in thermal contact.

 Temperature of hot soup will drop There is net heat transfer from the hot
 Temperature of cold metal spoon will rise soup to the cold metal spoon
 In the end, both objects achieve same temperature

[net heat transfer between two objects = 0 (zero)]
 Both objects are in thermal equilibrium

Cold metal spoon Metal spoon starts to Metal spoon becomes as hot
( = 30 ℃)
become hot as the soup
( = 40 ℃) ( = 40 ℃)

Heat from hot soup = Heat from hot soup = Heat from hot soup

Heat from spoon Heat from spoon Heat from spoon

Hot soup Soup starts to become cold Soup becomes as hot as the
( = 100 ℃) metal spoon
( = 80 ℃)
( = 40 ℃)

Diagram 1: Temperature change between two objects (soup and metal spoon) & flow of heat

2. Thermal equilibrium in daily life

a) Heating object

(i) Oven
 Hot air in oven is in thermal contact with cake batter
 Heat (hot air) flows to cake batter
 Cake batter is heated until it is baked

(ii) Clinical thermometer
 Thermometer is placed under the tongue of a patient
 Heat from patient flows to the thermometer until thermal equilibrium
 Temperature of patient = temperature of clinical thermometer

b) Cooling object

(i) Refrigerator
 Food is kept in the refrigerator
 Heat from food (hot) flows to the cold air in the refrigerator until

thermal equilibrium occurs
 Temperature of food drops, food stays fresh for a longer period

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(ii) Cold drinks
 Drinks are cooled by adding ice cubes
 Heat in the drink (hot) flows to the cold ice cubes (ice cubes absorb
heat from the drink) and melt
 Melted ice cubes absorb heat from the drink until thermal equilibrium
is achieved.

3. To calibrate a liquid-in-glass thermometer using two fixed points
 Calibration
 a process of making a scale of reading on a thermometer.
 The process of calibrating uses the thermometric property of liquid in glass.
 Thermometric property = a physical property (such as length of column of liquid in
thermometer) which can be measured and changes with
temperature.
 Thermometer that does not have a scale can be calibrated using two fixed
temperature points:
(i) Lower fixed point = Melting point of ice, 0℃
o it is determined by measuring the length of column of the liquid in the
thermometer which is placed in the ice and distilled water as shown
in Diagram 2.

Thermometer

Ice +
distilled
water

Diagram 2: The calibration to determine the melting point of ice

(ii) Upper fixed point = boiling point of water, 100 ℃
o it is determined by measuring the length of column of the liquid in the
thermometer which is placed in boiling distilled water as shown in
Diagram 3.

Retort to the power
stand supply

Immersion
heater
Boiling distilled
water

Diagram 3: The calibration to determine the boiling point of water

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 Diagram 4 shows the measurement of length, from 0 ℃ until ℃, and the
measurement of length, 100 from 0 ℃ until 100 ℃.

℃


Diagram 4: Measurement of length, 100 and 100

 The formula to determine temperature for an object/ liquid using calibration is

= × 100℃
100

 Example:

To determine temperature, : Alternative method:

(formula method) (ratio method)
100 = 12 100 = 12
= 4
12 = 100℃
= × 100℃ 100℃
100 1 = 12

= 4 × 100℃ 1 = 8.33 ℃
12
= 4
= 33.3 ℃ 1 × 4 = 8.33 ℃ × 4

4 = 33.3 ℃

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4.1 MIND MAP

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4.1 FAQ

No Question And Answer
1Q Does mass affect thermal equilibrium?

A If two objects have the same mass, the object with the higher temperature
has greater thermal energy. Temperature affects thermal energy, but
2Q temperature isn't the same thing as thermal energy. That's because an
A object's mass also affects its thermal energy.

3Q What is thermal equilibrium example?
A
Thermal equilibrium exists when two objects in thermal contact no longer a
4Q affect each other's temperature. For example, thermometer is placed in
A contact with the patient’s body. If both the body temperature of the
patient and that of the mercury (or alcohol) in the clinical thermometer have
5Q reached thermal equilibrium, then the temperature of the thermometer is
A the same as the body temperature, hence the reading of the thermometer
shows the body temperature of the patient.
6Q
A What happens to a hot cup of tea as it reaches thermal equilibrium?

For example, a hot cup of tea is not in thermal equilibrium with its
surroundings, there will be a net transfer of heat from the cup to the
surroundings. When they reach the temperature, each will stay at the same
common temperature as they are in thermal equilibrium.

What is the connection between heat and temperature?

Heat and temperature are related to each other, but are different
concepts. Heat is the total energy of molecular motion in a substance
while temperature is a measure of the average energy of molecular
motion in a substance.

What is the main difference between heat and temperature?

Heat measures both kinetic and potential energy contained by
molecules in an object. On the other hand, temperature measures
average kinetic energy of molecules in substance. The main feature
of heat is that it travels from hotter region to cooler region.

Why is thermal equilibrium important to us?

It is very important for the Earth to remain in thermal equilibrium in order
for its temperature to remain constant. The greenhouse effect slows down
the heat transfer from Earth to space, making the planet hotter.

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4.1 Exercise

SECTION A
1 Two objects that are in touch said to be in thermal equilibrium when

A achieve same temperature [Mengetahui]
B all heat from object a is transferred to object b
C all heat from object b is transferred to object a
D specific heat capacity object a is equal to object b

2 Diagram 2 shows cold milk being poured into hot tea.

Diagram 2

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Which statement is correct about the final temperature of the mixture?

A It is lower than the temperature of the cold milk.
B It is lower than the temperature of the hot tea.
C It is higher than the temperature of the hot tea.
D It is the same as the temperature of the cold milk.

[Memahami]

3 Diagram below shows block L and block M of different material in thermal
equilibrium.

Thermometer Thermometer
M
L

Which of following statements is true?

A specific heat capacity of L =specific heat capacity of M

B The net rate of heat transferred is equal

C The net rate of heat transferred is zero

D Temperature of L is higher than temperature of M.

[Memahami]

4. Diagram 4 shows two copper blocks L and M, in contact with each other. The initial
temperature of L and M are 50 0C and 30 0C respectively.

Diagram / Rajah 4
Which statement is correct when L and M are at thermal equilibrium?

A Temperature of L is higher than M

B The quantity of heat in L is the same as in M

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C Rate of change in temperature of L is bigger than that of M
D Net rate of heat flow between L and M is zero

[Memahami]

5. Diagram 5 shows a hot metal sphere immersed in cold water at 0°C.

Diagram 5
Thermal equilibrium is reached when the
A temperature of sphere > temperature of the water
B temperature of sphere < temperature of the water
C temperature of sphere = temperature of the water
D sphere begins to melt

[Mengetahui]

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SECTION B
1 Diagram 1 shows a mercury thermometer which has not been calibrated.

Diagram 1
a) i) State the changes physical properties for the mercury when the temperature increases.

[Mengetahui]

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

[1 mark]

ii) Why is mercury used in the thermometer? [Memahami]

.....................................................................................................................................
[1 mark]

b) The length of the mercury column in the thermometer is 2.6 cm at 0 0C and 22.6 cm at 100
0C.
i) What is the difference in the lengths of the mercury columns at 0 0C and 100 0C?

[Mengetahui]

[1 mark]

ii) When the thermometer is place in hot oil, the lengths of the mercury columns is
16.9 cm.
Calculate the temperature of the hot oil.

[mengaplikasi kuantitatif]

[2 mark]

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2 Diagram 2 shows a student conducts an experiment by putting a metal sphere with initial
temperature of 30oC into a beaker boiling water.

Diagram 2

a) i) What happen to the temperature of the metal sphere?

[Mengetahui]

…..................................................................................................................................
[1 mark]

ii) Give a reason for the answer in 2(a)(i).

[Memahami]

…..................................................................................................................................

[1 mark]
b) After sometime, the metal sphere and the boiling water have the same temperature.

(i) Tick (√ ) in the box below for the correct statement about heat flows between the
metal sphere and the boiling water.

[Memahami]

The rate of heat flows from boiling water < the rate of heat flows from
metal sphere.

The rate of heat flows from boiling water = the rate of heat flows from
metal sphere.

The rate of heat flows from boiling water > the rate of heat flows from
metal sphere.

[1 mark]

(ii) State the physics concept involve in 2(b) (i).

[Mengetahui]

…..................................................................................................................................
[1 mark]

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QR CODE

Title 4.1 Thermal Equilibrium QR CODE
link
THERMAL
EQUILIBRIUM https://youtu.be/pePjXWxDu1I
(Physics KSSM)

THERMAL https://youtu.be/Ft6L-ZlwO1M
EQUILIBRIUM
(PASTI SKOR)

THERMAL https://youtu.be/-7NVJ811E_0
EQUILIRIUM
(iptv)

THERMAL https://youtu.be/gzy4YFuKg9A
EQUILIBRIUM
(BOZEMAN
SCIENCE)

REINFORCEMENT https://drive.google.com/file/d/15DHHxRcn

TEST sFdDRRpldrGHwlcWH_brIEQB/view?usp

=sharing

ANSWER https://drive.google.com/file/d/1dkAL0CX

REINFORCEMENT HYKk1KyN26d7oMmdvUMPEOocA/view

TEST ?usp=sharing

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4.1 ANSWER

BAHAGIAN A/SECTION A

NO ANSWER
1 A
2 B
3 C
4 D
5 C

SECTION B

1 (a)(i) Mercury is expand when the temperature increase.
(ii) Mercury can be seen clearly / opaque

(b)(i) 22.6 cm – 2.6 cm = 20.0 cm
(ii) 22.6 - 2.6 /22.6 - 2.6 = 100 - x /100 - 0
5.7/20 = 100 – x / 100
570/20 = 100 – x
28.5 = 100 – x
x = 100 – 28.5
= 71.5 0C

2 a(i) Temperature increases 1
(ii) Metal sphere absorb heat 1
1
b(i) the rate of heat flows from boiling water = the rate of heat flows 1
from metal sphere.
(ii)
Thermal equilibrium

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