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Heat and Temperature

Distinguish between heat and temperature, explore thermal energy transfer, and learn about specific heat capacity.

Last updated: 10 March 2026

★★★☆☆ Level 3HeatTemperatureEnergyThermal4 min read

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Temperature vs. Heat

  • Temperature measures how hot an object is — the average kinetic energy of its particles. Measured in °C or K.
  • Heat (thermal energy) is energy transferred from a hotter object to a cooler one. Measured in joules (J).

Temperature Conversion

T(K)=t(°C)+273T(\text{K}) = t(°C) + 273

Absolute zero (0 K = −273 °C) is the lowest possible temperature.

Specific Heat Capacity

Different materials need different amounts of energy to heat up:

Heat Transfer

Q=m⋅c⋅ΔTQ = m \cdot c \cdot \Delta T

Q = heat (J), m = mass (kg), c = specific heat capacity (J/kg·K), ΔT = temperature change (K or °C).

Substancec (J/kg·K)
Water4 200
Iron450
Aluminium900
Air (dry)1 005

Water's high specific heat makes it excellent for storing and transporting heat.

Methods of Heat Transfer

  • Conduction — direct particle-to-particle transfer through a solid (e.g. metal spoon in hot soup).
  • Convection — transfer via moving fluid or gas (e.g. warm air rising in a room).
  • Radiation — electromagnetic waves carry energy without a medium (e.g. heat from the Sun).
Note Insulation (foam, wool, air gaps) slows conduction. Shiny surfaces reduce radiation absorption.
  1. 1

    Identify what is unknown

    Is it Q, m, c, or ΔT?
  2. 2

    Rearrange Q = mcΔT

    For example, ΔT = Q / (mc).
  3. 3

    Substitute values with units

    Keep masses in kg and ΔT in °C or K (same size).

How much heat is needed to warm 2 kg of water from 20 °C to 80 °C?

Q=2×4200×(80−20)=2×4200×60=504 000 J=504 kJQ = 2 \times 4200 \times (80 - 20) = 2 \times 4200 \times 60 = 504\,000 \text{ J} = 504 \text{ kJ}

Real world: car engine cooling system

A car engine uses water as a coolant because of its high specific heat capacity (c=4200 J/kg\cdotpKc = 4200\text{ J/kg·K}). 3 kg of water absorbs heat: Q=3×4200×40=504 000 JQ = 3 \times 4200 \times 40 = 504\,000\text{ J} when engine temperature rises 40°C above coolant temperature. The high cc means water absorbs a large amount of energy for a small temperature rise, keeping the engine from overheating.

Real world: weather forecasting and coastal climates

Coastal cities have milder climates than inland cities because the sea (water) has a much higher specific heat capacity than land (rock/soil). The sea absorbs heat in summer without warming as much and releases it slowly in winter, moderating the air temperature. This principle is fundamental to climate science.

Real world: cooking thermometers

A chef uses a food thermometer that converts temperature in Celsius to a meaningful reading: a joint must reach 75°C (= 348 K) at the core to kill harmful bacteria. The thermometer measures the kinetic energy of particles — the physical basis of temperature — to ensure food safety.

Tip In the formula Q=mcΔTQ = mc\Delta T, make sure ΔT\Delta T is the temperature change, not the final temperature. If water warms from 20°C to 80°C, ΔT=60\Delta T = 60°C (not 80).

Practice Problems

Convert 100 °C to kelvin.

Show answer
T = 100 + 273 = 373 K.

How much heat is released when 0.5 kg of iron cools from 200 °C to 50 °C? (c = 450 J/kg·K)

Show answer
Q = 0.5 × 450 × 150 = 33 750 J.

Name the dominant method of heat transfer in a metal frying pan.

Show answer
Conduction.