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Physics · Class 10 · Chapter 11: Heat

8 min

Key points

Heat is a form of energy that flows from hot body to cold body due to temperature difference
Temperature is the degree of hotness or coldness of a body measured on a definite scale
Specific heat capacity is the amount of heat required to raise the temperature of unit mass of a substance through 1°C
Heat capacity is the amount of heat required to raise the temperature of the whole body through 1°C
Latent heat of fusion is the amount of heat required to convert unit mass of solid into liquid at constant temperature
Latent heat of vaporization is the amount of heat required to convert unit mass of liquid into vapour at constant temperature
Heat is transferred by three methods: conduction, convection and radiation
Good conductors like metals have free electrons which transfer heat energy quickly
Convection occurs in liquids and gases due to density differences caused by heating
All hot bodies emit heat radiations which travel at the speed of light

Definitions

Heat: Heat is a form of energy that flows from a hot body to a cold body when they are in thermal contact.
Temperature: Temperature is the degree of hotness or coldness of a body measured on a definite scale like Celsius or Fahrenheit.
Specific Heat Capacity: Specific heat capacity of a substance is the amount of heat required to raise the temperature of unit mass of that substance through 1°C.
Thermal Equilibrium: Two bodies are said to be in thermal equilibrium when there is no net flow of heat between them.
Latent Heat: Latent heat is the amount of heat required to change the state of unit mass of a substance at constant temperature and pressure.

Worked example

Define heat and temperature. State any two differences between them. (5 marks)

Heat: Heat is a form of energy that flows from a body at higher temperature to a body at lower temperature. Temperature: Temperature is the degree of hotness or coldness of a body. Differences: (1) Heat is a form of energy while temperature is the degree of hotness. (2) Heat is measured in Joules while temperature is measured in Celsius or Kelvin.

Common mistakes

Students confuse heat with temperature - remember heat is energy, temperature is degree
Forgetting to write units in numerical problems (J, cal, J/kg°C)
Mixing up latent heat of fusion (80 cal/g) with vaporization (540 cal/g)
Not mentioning 'at constant temperature' when defining latent heat
Drawing conduction diagram without showing particle vibrations

Quick recap

Heat is energy transfer from hot to cold bodies, measured in Joules. Temperature is degree of hotness, measured in Celsius/Kelvin. Heat transfers through conduction (direct contact), convection (fluid movement), and radiation (electromagnetic waves). Use Q = mcΔT for heat calculations where m is mass, c is specific heat capacity, and ΔT is temperature change.

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