Measuring Specific Heat Capacity

This experiment determines the specific heat capacity of a solid block or a liquid.

Method for a solid block

1. Measure the mass of the metal block ($m$) using a balance.
2. Insert a thermometer and an electric heater into holes drilled in the block.
3. Record the initial temperature ($\theta_1$).
4. Switch on the heater. Record the voltage ($V$) and current ($I$).
5. Heat for a measured time ($t$).
6. Record the final temperature ($\theta_2$).
7. Calculate: $c = \frac{VIt}{m(\theta_2 - \theta_1)}$

Method for a liquid

1. Measure the mass of the liquid in a calorimeter.
2. Insert a thermometer and an immersion heater.
3. Stir the liquid throughout to ensure even heating.
4. Follow the same measurement procedure as above.

Sources of error

• Heat loss to surroundings: causes the measured $c$ to be higher than the true value (some energy heats the surroundings, not just the sample).
• Heat absorbed by the container: the container also gains thermal energy, so the measured $c$ is higher.

Reducing errors

• Insulate the block or calorimeter (lagging, lid).
• Use a smaller temperature rise (less heat loss).
• Use a cooling correction: monitor temperature after the heater is turned off.
• For liquids, stir continuously for uniform temperature.

Common errors and how to correct them

• Forgetting to subtract the initial temperature ($\Delta\theta = \theta_2 - \theta_1$, not just $\theta_2$).
• Not converting units (mass must be in kg, not g).

How to apply this in an exam

State the measurements needed (mass, temperature change, voltage, current, time). Write the equation linking electrical energy to thermal energy. Describe how to reduce heat losses.