Understanding Temperature Change in Substances: Heat and Specific Heat Capacity

Many people assume that when two substances are heated with the same amount of thermal energy, they will experience the same temperature change. However, this is not necessarily true. The temperature change of a substance depends significantly on its specific heat capacity, a property that varies greatly between different materials. This article explores the relationship between thermal energy, mass, specific heat capacity, and temperature change.

Thermal Energy and Temperature Change

The relationship between thermal energy, mass, specific heat capacity, and temperature change can be described by the formula:

Q  mc ΔT

where:

(Q): the amount of thermal energy added in joules (m): the mass of the substance in kilograms (c): the specific heat capacity in joules per kilogram per degree Celsius (ΔT): the change in temperature in degrees Celsius

From this equation, it is clear that for the same amount of thermal energy added ((Q)), the temperature change ((ΔT)) will differ if the specific heat capacities ((c)) of the substances are different. Generally, substances with a lower specific heat capacity will experience a more significant temperature change for the same amount of energy added compared to substances with a higher specific heat capacity.

Examples and Insights

The outcome is unlikely to be the same for two substances of different mass and specific heat capacities. For example, consider heating a kilogramme of water and a kilogramme of aluminum foil with the same amount of thermal energy. Water requires 4800 joules to increase its temperature by 1 degree Celsius, whereas aluminum foil only requires 900 joules.

Burn the Fingers Experiment: A Practical Demonstration

While you may think that holding a match to your two fingers will result in the same temperature change (burn), this experiment can be interesting to set up as a practical demonstration. By observing and recording the results, you can better understand the principles of thermal energy and temperature change in different materials.

Thermal Energy vs. Internal Energy and Temperature

Thermal energy is the part of a substance's internal energy that results from the motion of its molecules and contributes to its temperature. However, internal energy is an extensive property of a system, meaning it depends on the size of the system. A small cup of water and a large swimming pool both have the same temperature but the pool contains much more internal and thermal energy due to its larger volume.

Conclusion

Understanding the relationship between thermal energy, mass, specific heat capacity, and temperature change is crucial for grasping the principles of heat and energy transfer. By recognizing the role of specific heat capacity, we can better predict and explain temperature changes when heating different substances.