4.3.2.2 - Temperature Changes and Specific Heat Capacity

What controls temperature rise

Heating transfers energy to a system. If the temperature of the system increases, the temperature rise depends on three things:

• the energy input to the system
• the mass of the substance heated
• the type of material

For the same mass and material, a larger energy input gives a larger temperature rise. For the same energy input and material, a larger mass gives a smaller temperature rise because the transferred energy is shared across more matter. For the same energy input and mass, different materials can have different temperature rises.

[DIAGRAM: asset_name: Temperature Rise Factors - diagram 1; asset_slug: 033_4_3_2_2_temperature_changes_and_specific_heat_capacity_diagram1; file: diagram_assets/033_4_3_2_2_temperature_changes_and_specific_heat_capacity_diagram1.png; recommended_method: image_gen; description: Qualitative comparison visual with three labelled panels: more energy input gives a larger temperature rise for the same mass and material; a larger mass gives a smaller temperature rise for the same energy input and material; and a high specific heat capacity material has a smaller temperature rise than a low specific heat capacity material for the same energy input and mass. This is not an assessed calculation diagram; nearby prose gives the exact assessed wording.]

The important pattern is that temperature rise is larger when more energy is transferred, but smaller when the same energy is spread through more mass or through a material that needs more energy for each degree of warming.

What specific heat capacity means

Specific heat capacity describes how much energy a material needs for its temperature to rise. It is a property of the material, so different substances have different specific heat capacities.

The unit is joules per kilogram per degree Celsius, written as J/kg °C. For example, if a material has a specific heat capacity of 900 J/kg °C, then 900 J is needed to raise the temperature of 1 kg of that material by 1 °C.

A material with a high specific heat capacity needs a large energy transfer for each kilogram to warm by 1 °C. That means, for the same mass and same energy input, a high-specific-heat-capacity material has a smaller temperature rise than a low-specific-heat-capacity material.

This is the opposite of a common misconception: a higher specific heat capacity does not mean the material warms more quickly. It means the material needs more energy for the same temperature rise.