Investigating Specific Heat Capacity

Specific heat capacity tells us how hard it is to heat a material. Water warms slowly; sand warms quickly. This is because different materials need different amounts of energy to raise their temperature.

Key idea and formula

Specific heat capacity (c) is the energy needed to raise the temperature of 1 kg of a substance by 1°C. Units: J kg⁻¹ °C⁻¹.

Energy, mass, and temperature change are linked by:

$$Q = mc\,\Delta T$$

If an electric heater is used: $$Q = V I t$$ so $$c = \dfrac{V I t}{m\,\Delta T}$$

Measuring c for a solid (electrical method)

• Apparatus: metal block with holes, immersion heater, thermometer, insulation (lagging), balance, power supply, ammeter, voltmeter, stopwatch.
• Measure the block’s mass m.
• Insert heater and thermometer, wrap the block to reduce heat loss.
• Record initial temperature. Switch on power. Keep V and I steady. Time for t seconds.
• Stir or gently move the thermometer for an even temperature. Record final temperature, find $\Delta T$.
• Calculate $Q=VIt$, then $c=Q/(m\Delta T)$.

Measuring c for a liquid (insulated cup)

• Apparatus: polystyrene cup with lid, immersion heater, thermometer, balance, power supply, ammeter, voltmeter, stopwatch.
• Measure mass of liquid m (weigh cup empty and full).
• Heat the liquid for time t, recording V and I. Stir gently. Note $\Delta T$.
• Use $c = V I t / (m\,\Delta T)$. The cup also warms a little, so insulate well and use a lid to reduce errors.

Method of mixtures (no electricity)

A hot solid placed in cooler water: heat lost by solid = heat gained by water.

$$m_s c_s (T_h - T_f) = m_w c_w (T_f - T_i)$$

Measure masses and temperatures, then solve for the unknown $c_s$.

Common misconceptions

• “Higher temperature means more energy added” – only true if mass and c are the same. Energy depends on m and c as well as $\Delta T$.
• Confusing heat and temperature: heat is energy transferred (Q); temperature measures how hot something is.
• Forgetting container absorbs energy; use good insulation and keep experiments brief.

Real-world link: Metal spoons feel colder than wooden ones because metals have lower c and conduct heat better; oceans warm slowly due to water’s high c.