4.2 SPECIFIC HEAT CAPACITY

CHAPTER 4
HEAT

4.2 SPECIFIC HEAT CAPACITY

TEXT BOOK : PAGE 125 - 136

SUE ROSE



4.2 SPECIFIC HEAT CAPACITY

LEARNING
STANDARD 1

4.2.1 Explain heat capacity, C

The sun heats up the sand However, sand gets hot
and sea water at the same quickly and sea water gets
period of time hot slowly

This can be explained Sea water has a high
based on the concept heat capacity and gets

of heat capacity hot slowly

Different objects have
different heat capacity

Sand has a low heat
capacity and gets hot

quickly

During morning
A boy puts a pail of water from a

swimming pool near the pool

During afternoon
The boy puts one hand into the

pail and another hand in the
swimming pool

He observes that both
temperatures are different

Water in the pail is hotter than
water in the pool

The water in the pool and in the pail have
different heat capacity.

Water and cooking oil It is observed that the temperature
which have the same mass of the cooking oil rises faster than
is heated with the same the water temperature
amount of heat
Water and cooking oil have different
specific heat capacity

What is the
meaning of …..

Heat capacity? Specific Heat
Capacity?

Activity 1: A pail of water from a swimming

Aim: Investigate heat capacity pool has been left for several hours
beside the pool.

(a) Which water is hotter?

Water in the pail

(b) Which water has smaller mass?

Water in the pail

(c) Which water needs to be exposed to the sunlight in a
shorter time in order to raise its temperature by 1 ⁰C?

Water in the pail

Activity 1:
Aim: Investigate heat capacity

(d) Which has larger heat capacity, water in
the pail or water in the swimming pool?

Water in the pool

(e) Make an inference about relationship between heat capacity and
temperature rises of a substance.

The higher the heat capacity,
the lower the temperature rises

DEFINITION OF HEAT CAPACITY

Heat Capacity, C of an object is the quantity
of heat needed to raise the temperature of

the object by 1°C

C=Q Q = quantity of heat supplied

Δθ Δθ = change in temperature

Unit C = J ⁰C-1

Activity 1 Aim: Investigate heat capacity

2. When 2000 J of heat is supplied to objects X and Y, object X experiences a
rise in temperature of 1 ⁰C and object Y by 2 ⁰C.

(a) What is the heat capacity of ? (b) Compare heat capacity

(i) Object X? (ii) Object Y? Heat capacity Y <
Heat capacity X
CX = 2000 J CY = 2000 J
1 ⁰C 2 ⁰C (c) Compare the increase in
temperature
= 2000 J ⁰C-1 = 1000 J ⁰C-1

(b) Which object is hotter Increase in temperature Y >
Increase in temperature X

Object Y is hotter Object with smaller heat capacity
heats up faster

Object A and B are made from aluminium but
have different heat capacity because
different masses.

Object A of mass Object B of mass
1 kg needs 900 J 2 kg needs 1800 J
of heat to rise up of heat to rise up
temperature by temperature by
1 °C. 1 °C.

CA = 900 J ⁰C-1 CB = 1800 J ⁰C-1

Heat capacity B > Heat capacity A

The higher the mass of an object,
the higher the heat capacity

Both kettle P and Q are switched on to heat up water until boiling.

(a) Which kettle boils in longer time? Kettle Q
(b) Which kettle has larger quantity of heat? Kettle Q

(c) Which kettle has larger heat capacity? Kettle Q

(d) Make an inference about the relationship between heat capacity and
mass of a substance

The greater the mass,
the greater the heat capacity

(e) What factors affect the heat capacity?

Mass Change in temperature Material of
substance

Activity 2 Aim : Investigate daily situations which involve
heat capacity

1. Explain why a cup of hot coffee can cause more injury
on a body than a drop of hot coffee.

Water from a cup of hot coffee has
higher heat capacity compared to a drop

of hot coffee on a body.

Activity 2 Aim: Investigate daily situations which involve
heat capacity

2. Explain why the metal parts of a car get hot
faster while the plastic and other material stay
at more bearable temperature

The dashboard of a car has a lower
heat capacity compared to the
cushion.

Absorption of heat energy from the
Sun causes the dashboard to get hot
faster compared to the cushion.

Activity 2 Aim: Investigate daily situations which involve
heat capacity

After being left to cool for some
time, the soup in a large bowl is
hotter compared to the same soup
in a small bowl

The soup in the large bowl has
greater heat capacity
So it will cools down at slower rate

Activity 2 Aim: Investigate daily situations which involve
heat capacity

3. Explain why children like walking on the water
compare to the sand on hot day.

Sand and sea water receive the same
amount of heat
But sand heats up faster and sea water
heats up very slow

Sand has low heat capacity and heats
up faster
Water has high heat capacity and
heats up slowly

Activity 2 Aim: Investigate daily situations which involve
heat capacity

4. Explain why the jam of a hot apple pie It is easier to eat the
burns but the crust can be eaten instantly crust because it cools
down faster compared
We can touch the crust
to apple jam which is
still hot

Apple jam is very hot The crust and the apple
jam has different heat
capacity

Heat capacity
of apple jam
is greater

Activity 2 Aim: Investigate daily situations which involve
heat capacity

5. A watermelon and sandwich are taken out from
a fridge. After 30 minutes, the watermelon is
cooler than the sandwich. Why does the
watermelon stay cool for a longer time than a
sandwich even tough both are taken out from
the same fridge?

Watermelon cools down faster compared to
the sandwich
Heat capacity of the watermelon is smaller,
so the decreases in temperature of
watermelon is faster

LEARNING
STANDARD 2

4.1.2 Define specific heat
capacity of a material,
c = Q/mθ

Activity 3 Aim : Investigate specific heat capacity

Different quantity of heat is needed to raise
the temperature by 1 ⁰C for two objects A and
C even though their masses are equal.
This is because the two objects are made from
different material. Different substance has
different specific heat capacity.

Which substance needs large amount of heat to
raise temperature by 1 ⁰C.

Aluminium

Activity 3 Aim: Investigate specific heat capacity

1 kg of plumbum (Pb) needs 130 J
of heat and 1 kg of Aluminium

needs 900 J of heat to raise the
temperature by 1 ⁰C

Plumbum heats up faster than
Aluminium because it needs less

amount of heat to raise
temperature by 1 ⁰C

Definition of Specific Heat Capacity

The quantity of heat needed to raise the
temperature of 1 kg mass of the substance by 1 °C

Heat J
Mass kg

Rises of temperature °C
Specific heat capacity J kg-1°C-1

Quantity of heat, J Increase in temperature, °C

Mass, kg
Specific heat capacity, J kg-1°C-1

1. What is the meaning of the specific heat
capacity of aluminium 900 J kg-1 ⁰C-1?

1 kg of aluminium needs 2. What is the meaning of the specific
900 J of heat to raise its heat capacity of water is
temperature 1 °C 4200 J kg-1 ⁰C-1?

1 kg of water needs
4 200 J of heat to
raise its
temperature by 1 °C.

A metal has mass 2 kg. Calculate the amount of heat
that must be transferred to the metal to raise the
temperature from 30 ⁰C to 70 ⁰C.
(specific heat capacity of the metal = 500 J kg -1 ⁰C-1 )

m = 2 θ = 70-30 = 40 c = 500

Q = mcθ = (2)(500)(70 – 30) = 40,000 J

4. How many joules of energy are required to raise the
temperature of 100 g of gold from 20 ⁰C to 100 ⁰C?
(specific heat capacity of gold = 129 J kg-1 C-1)

m = 0.1 θ = 100-20 = 40 c = 129
Q = mcθ = (0.1)(129)(80) = 1 032 J

LEARNING
STANDARD 3

4.1.3 Experiment to determine :

(i) The specific heat
capacity of water

(ii) The specific heat
capacity of aluminium

Experiment 4.1 Aim: To determine the specific heat capacity of water

Apparatus: Power supply, immersion heater, beaker, stopwatch, thermometer, retort stand,
electronic balance.

1. Wrap the beaker with tissue paper. 3. Fill water in the beaker until ¾ full.
2. Put the beaker on an electric beam
4. Take the reading of water, m as shown
and set the reading of the balance
to zero. on the electronic balance.

5. Take the reading of the water initial
temperature, θ1.

6. Switch on the heater
and start the stopwatch.

7. After 5 minutes, turn off
the immersion heater.

Take the reading of the
highest temperature as
the final temperature, θ2

36 W

0.42 kg
5 x 60 = 300 s

27.0 ⁰C
33.0 ⁰C
6.0 ⁰C

Q = Pt = 36 W x 300 s = 10,800 J

Q = mcθ = 10,800 J

Q = mcθ = 10,800 J c = 4 286 J kg-1 ⁰C-1
c = 10,800 = 10,800

mθ (0.42)(6)

Discussion :

1. Why does the beaker need to be wrapped with cloth?

To reduce heat lost to the surrounding

2. Why the final temperature, θ2 not taken as soon as the five-minute
heating time ends?

To ensure thermal equilibrium is achieved between the water
and the thermometer.

3. Given specific heat capacity of water is 4 200 J kg-1 ⁰C-1. Compare the
value of specific heat capacity of water obtained from the experiment
with the value given. Explain the difference between the two values.

The value of from the experiment is bigger
There is heat lost, θ is lower from the expected value
Formula c = Q

mθ, c bigger if θ is smaller

Experiment 4.2 Aim: To determine the specific heat capacity of aluminium

Apparatus: Power supply, immersion heater, stopwatch, thermometer, a 1 kg aluminium
cylinder, felt cloth, a small amount of oil

1. Take the reading of the initial 3. After five minutes, turn off the heater.
temperature of the block, θ1 and record
the reading. Take the reading of the highest
temperature as the final temperature, θ2.
2. Switch on the immersion heater and at
Record the reading.
the same time start the stopwatch.

50 W
1 kg
5 x 60 = 300 s
27 ⁰C
42 ⁰C
15 ⁰C

Q = Pt = 50 x 300 = 15,000 J

15,000 J

Q = mcθ = 15 000 J
c = 15,000 = 15,000 c = 1000 J kg-1 ⁰C-1

mθ (1)(15)

Discussion.

1. What can be done to obtain a better thermal contact between
the bulb of thermometer and the aluminium block?

Put a small amount of oil in the hole.

2. Given specific heat capacity of water is 900 J kg-1 ⁰C-1. Compare the
value of specific heat capacity of water obtained from the experiment
with the value given. Explain the difference between the two values.

The value of from the experiment is bigger.
There is heat lost, θ is lower from the expected value.
Formula c = Q

mθ, c bigger if θ is smaller.

LEARNING
STANDARD 4

4.1.4 Communicate to explain
the applications of
specific heat capacity in
daily life, material
engineering and natural
phenomena

Application of Specific Heat Capacity

Characteristics of a small value of specific heat capacity

Heats up and Sensitive to the change
cools faster of temperature

Characteristics of big value of specific heat capacity

Heats up and Can absorb a large amount
cools slower of heat.

For example, water acts a heat reservoir as it can absorb a
great amount of heat before it boils. Water is used as a
cooling agent in a car radiator.



Cooking Pot

Copper base :

• Low specific heat capacity.
• The pot becomes hot very quickly.
• This enables quick cooking of the food in the pot.
• High density.
• The heavier base ensures that the pot is stable and will not topple over easily.

BODY : HANDLE :
Plastic
Aluminium High specific heat capacity.
Poor heat conductor
Low specific heat
capacity. BASE :
Copper
Heats up quickly Low specific heat capacity.
Heats up very quickly.

Wooden handle :
• Large specific heat capacity.
• The handle will not become too hot when heat is absorbed.
• Poor conductor of heat.

Alumni body :

• Relatively low specific heat capacity.
• The pot becomes hot quickly.
• Low density so it will be lighter
• Does not react with the food in the pot

Body Wooden
Handle

Base

1. During the day, heat is Sea Breeze 4. Warm air above the
absorbed by the land land rises. Becomes
and the sea The movement of cool low pressure
air from sea to land

5. Cool air from the
sea (high pressure)
moves towards the
land as sea breeze.

2. Sea has a high specific heat 3. Land has a low specific heat capacity
capacity which temperature which temperature increases faster.
increases slower. Land is warmer than sea.

Land Breeze 4. Cool air from the
land (high pressure)
The movement of cool air moves towards the
from land to sea sea to replace the
rising air
3. Hot air above
the sea rises.
Low pressure

2. Sea is hotter than the land 1. Land loses heat faster than sea at night
which loses heat slower. due to its low specific heat capacity

Cooling system of a car engine

Water is used as coolant :
• High boiling point – not change to gas easily
• High specific heat capacity so can absorb a lot of heat.
• Abundant, Economical – so cheaper & save cost

Heat is released to the cooler air The hot water flows to the
that flows through the cooling fans. radiator

Pumps the water into Heat produced by the engine is
the engine block absorbed by the water



Selection Building materials of traditional house
in various climate – Warm climate

Materials for houses in warm climate :

WOOD

Reason:

Wood has a high specific heat
capacity and gets hot slowly.
In warm weather region, traditional
houses are built from wood which
functions as an insulator of heat
from the scorching sun.