Specific Heat Capacity
The specific heat capacity (c) of a substance is the energy required per unit mass per unit temperature increase .
Definition & Formula
c = E / [ m × (θ₂ − θ₁) ]
or E = m c (θ₂ − θ₁)
Units: J kg⁻¹ °C⁻¹
Experimental Determination (Aluminium Block Method)
Measurements Required
- Mass of aluminium block (m)
- Initial temperature (θ₁) and final temperature (θ₂)
- Voltage (V), Current (I) and Time (t) for which heat is supplied
Energy Supplied
Electrical energy is given by E = V × I × t.
Therefore, c = (V × I × t) / [m × (θ₂ − θ₁)]
Sources of Error & Precautions
Heat Loss and Corrections
- If the block is not insulated, heat escapes to the environment → temperature rise smaller → c appears larger.
- Use lagging or insulation around the block to reduce heat losses.
- Polish or paint the surface white to reduce radiation loss.
- Place a lid on the block to prevent convection currents.
- Reduce draughts in the room.
Typical Values & Observation
Water has a very high specific heat capacity:
- Takes a long time to heat up and to cool down.
- Requires large amount of energy → expensive for heating.
- Helps stabilise climate and body temperature in living organisms.
Summary Table
| Quantity | Symbol | Typical Unit | Formula |
|---|---|---|---|
| Energy transferred | E | joule (J) | E = m c Δθ |
| Mass | m | kilogram (kg) | |
| Specific heat capacity | c | J kg⁻¹ °C⁻¹ | |
| Temperature change | Δθ | °C (or K) |
Alternative Form
c = ΔE / (m Δθ)
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