Practice Model of Water - 3.2.2 Temperature Changes in a System and Specific Heat Capacity (GCSE Physics AQA)

Temperature Changes in a System and Specific Heat Capacity

Changing the Temperature

When we raise the temperature of a system, different factors will affect the increase in temperature. They include the following:

1. Mass of the substance heated – as the mass of the substance increases, the number of particles in the substance increases. This means that there are a larger number of particles to heat, therefore making it more difficult to heat.
2. Type of material – certain materials are easier to heat than others. For example, we can look at conductors and insulators; conductors are fairly easy to heat, whilst insulators are difficult to heat up.
3. Energy input – as the amount of energy input increases, it is easier to heat a substance. This is because we simply have more energy available in the system, which can be converted into kinetic energy, potential energy and thermal energy.

Calculating Temperature Changes

Formula for Change in Thermal Energy

We can calculate the change in thermal energy using the following formula.

change in thermal energy = mass × specific heat capacity x temperature change
∆E=mc∆θ

Where:

• change in thermal energy, ∆E, in joules, J
• mass, m, in kilograms, kg
• specific heat capacity, c, in joules per kilogram per degree Celsius, J/ kg °C
• temperature change, ∆T, in degrees Celsius, °C.

Question: Rebecca has an iron block, with a mass of 2 kg. She heats up the block using a heater, so the temperature increases by 5 °C. Calculate the energy transferred by the heater, given that the specific heat capacity of iron is 450 J / kg °C.

1. Write out the equation.

∆E=mc∆θ

2. Substitute in the numbers.

∆E = 2 x 450 x 5
∆E = 4500 J

Specific Heat Capacity

We previously covered this section in Chapter 1 Energy. For completeness, we are going to recap the definition here:

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.