Summary GCE GCSE IGCSE Secondary School High School Physics - Thermal Properties & Temperature

IGCSE Physics\Thermal Properties & Temperature\Important Concepts


IGCSE PHYSICS
THERMAL PROPERTIES AND TEMPERATURE: IMPORTANT CONCEPTS



TEMPERATURE CHANGE DURING HEATING AND COOLING

The particles in a substance contain stored energy known as internal energy. The
internal energy of the particles comprises of kinetic energy (which is due to the
motion of the particles) and potential energy (which is due to the forces of
attraction and repulsion between the particles).
When heat is supplied to an object, part of the thermal energy supplied goes into
the internal energy of the particles as kinetic energy. This causes the particles to
vibrate more vigorously or move at higher speed, hence the temperature of the
object increases.
Likewise, when an object is cooled, the particles lose some kinetic energy, causing
them to vibrate less vigorously or move at lower speed, causing the temperature of
the object to decrease.

The amount of thermal energy required to raise the temperature of an object by 1
Kelvin or 1 degree Celsius is known as the heat capacity of the object.


Heat capacity, C =

The unit for heat capacity, C, is Joules per degree Celsius (J °C-1).

A higher heat capacity of an object indicates more energy is required to raise the
temperature of the object by 1°C. Likewise, the same amount of energy is released
from the object when it is cooled by 1°C.

Objects made of the same material have the same specific heat capacity. Specific
heat capacity is defined as the amount of thermal energy required to raise the
temperature of 1 kilogram of a substance by 1 Kelvin or 1 degree Celsius.


Specific heat capacity, c =

The unit for specific heat capacity, c, is Joules per kilogram per degree Celsius
(J kg-1 °C-1).

Rearranging the formula for specific heat capacity:

Energy required, E (J)
= Mass, m (kg) x Specific heat capacity, c (J kg-1 °C-1) x Change in temperature,
(°C)

Application of the high specific heat capacity of water:
(a) Water has a high specific heat capacity of 4200 J kg-1 °C-1.
(b) Water requires a lot of thermal energy to be warmed up, and once it is warmed
up, it does not lose its energy easily.


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, IGCSE Physics\Thermal Properties & Temperature\Important Concepts


(c) Water is commonly used as a cooling agent in engines as water is able to
absorb large amounts of heat released from the engine without showing a
large increase in temperature.

Test Yourself:

1. When 575 J of thermal energy is removed from an iron cube of mass 50 g, the
temperature of the iron cube drops from 55°C to 30°C. Determine:
(a) the heat capacity of the iron cube




(b) the specific heat capacity of iron




2. °C is E
Joules. How much energy, in terms of E, is required to heat copper block B of
°C?




3. An electric kettle contains an immersion heater of power 2000 W. 2.0 kg of water,
originally at temperature 30°C, is heated in the kettle.
(a) Given that the specific heat capacity of water is 4200 J kg-1 °C-1, find the time
required for the water to boil.




(b) In reality, a greater amount of time than that calculated in (a) is required to
boil the water. Why?
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