MEASUREMENT OF HEAT ENERGY
Measurement of Heat Energy
Heat energy is the energy that is transferred from one place to another as a result of
temperature difference. Heat energy always flow from a region of high temperature to the
region of lower temperature. Heat energy is called thermal energy. It is measured in joule.
Heat Capacity
Heat capacity is the quantity of heat energy that is require to raise the temperature of a given
mass of an object by one Kelvin. The unit of heat /thermal capacity is joule per Kelvin (J/K or JK
-1
)
Formula of Heat Capacity
The formula for calculating heat capacity is as stated:
Heat Capacity Cp = mass (m) * Specific heat capacity (c)
Cp = m*c. ( Cp is also called thermal capacity )
Application of Formula:
Worked Examples:
I. Calculate the heat capacity of a mass 258kg if its specific heat capacity is 900J/KgK
Solution:
Data given in the question:
Mass = 258kg, specific heat capacity, c = 900J/kgK
Formula: heat capacity = mass * specific heat capacity
Substitution: Cp = 258 * 900.
Cp = 232200J/K
II. The thermal capacity of an object is 585 JK-1. Calculate the mass of the object if its specific
heat capacity is 390 kg-1K-1
Solution:
Data given in the question:
heat capacity =585 JK-1,specific heat capacity is 390 kg-1K-1
, Formula: thermal capacity Cp = mass * specific heat capacity
Substitution: 585 = m * 390
Make mass the subject: m = 585 ÷ 390.
m = 1.5 Kg
III. Determine the specific heat capacity of a substance whose mass is 200 grams and of
thermal capacity 250 JK-1
Solution:
Data given in the question:
Mass = 200g = 200÷1000 = 0.2 Kg thermal capacity Cp = 250 JK-1
Formula: thermal capacity = mass * specific heat capacity
Substitution: 250 = 0.2 * specific heat capacity, c
Make c the subject: specific heat capacity = 250 ÷ 0.2
Specific heat capacity = 1250 JKg-1 K-1.
Specific Heat Capacity
Specific heat capacity of a substance is the quantity of heat that is required to raise the
temperature of 1 kg mass by 1°C or 1Kelvin.
Formula of Specific Heat Capacity
The quantity of heat that is required to raise the temperature of a substance by 1 K is directly
proportional to the mass of the substance, the temperature change the substance.
Mathematically,
Quantity of heat H or Q = Mass of substance * temperature change
H = c*m*ΔӨ
If we make c the subject t, then we ill get, c = H/mΔӨ
H is quantity of heat measured in Joule, m is mass of substance measured in kg, Ө is
temperature measured in °C or K.
Measurement of Heat Energy
Heat energy is the energy that is transferred from one place to another as a result of
temperature difference. Heat energy always flow from a region of high temperature to the
region of lower temperature. Heat energy is called thermal energy. It is measured in joule.
Heat Capacity
Heat capacity is the quantity of heat energy that is require to raise the temperature of a given
mass of an object by one Kelvin. The unit of heat /thermal capacity is joule per Kelvin (J/K or JK
-1
)
Formula of Heat Capacity
The formula for calculating heat capacity is as stated:
Heat Capacity Cp = mass (m) * Specific heat capacity (c)
Cp = m*c. ( Cp is also called thermal capacity )
Application of Formula:
Worked Examples:
I. Calculate the heat capacity of a mass 258kg if its specific heat capacity is 900J/KgK
Solution:
Data given in the question:
Mass = 258kg, specific heat capacity, c = 900J/kgK
Formula: heat capacity = mass * specific heat capacity
Substitution: Cp = 258 * 900.
Cp = 232200J/K
II. The thermal capacity of an object is 585 JK-1. Calculate the mass of the object if its specific
heat capacity is 390 kg-1K-1
Solution:
Data given in the question:
heat capacity =585 JK-1,specific heat capacity is 390 kg-1K-1
, Formula: thermal capacity Cp = mass * specific heat capacity
Substitution: 585 = m * 390
Make mass the subject: m = 585 ÷ 390.
m = 1.5 Kg
III. Determine the specific heat capacity of a substance whose mass is 200 grams and of
thermal capacity 250 JK-1
Solution:
Data given in the question:
Mass = 200g = 200÷1000 = 0.2 Kg thermal capacity Cp = 250 JK-1
Formula: thermal capacity = mass * specific heat capacity
Substitution: 250 = 0.2 * specific heat capacity, c
Make c the subject: specific heat capacity = 250 ÷ 0.2
Specific heat capacity = 1250 JKg-1 K-1.
Specific Heat Capacity
Specific heat capacity of a substance is the quantity of heat that is required to raise the
temperature of 1 kg mass by 1°C or 1Kelvin.
Formula of Specific Heat Capacity
The quantity of heat that is required to raise the temperature of a substance by 1 K is directly
proportional to the mass of the substance, the temperature change the substance.
Mathematically,
Quantity of heat H or Q = Mass of substance * temperature change
H = c*m*ΔӨ
If we make c the subject t, then we ill get, c = H/mΔӨ
H is quantity of heat measured in Joule, m is mass of substance measured in kg, Ө is
temperature measured in °C or K.
