Specific Heat Capacity

2.2.2 Specific Heat Capacity

This section focuses on understanding the relationship between temperature change and internal energy in an object. We will explore the concept of specific heat capacity and how it affects the amount of energy required to raise the temperature of a substance.

Key Concepts

• Internal Energy: The total energy associated with the random motion of the atoms and molecules within a substance.
• Temperature: A measure of the average kinetic energy of the particles in a substance.
• Specific Heat Capacity (c): The amount of heat energy required to raise the temperature of 1 kg of a substance by 1 degree Celsius (or 1 Kelvin). It is a material property.

The Relationship Between Heat and Temperature Change

When heat energy is added to an object, the internal energy of the object increases. This increase in internal energy manifests as an increase in the average kinetic energy of the particles, which we perceive as a rise in temperature.

The amount of heat energy required to raise the temperature of an object depends on two factors:

1. The mass of the object (m)
2. The specific heat capacity of the material (c)
3. The change in temperature (ΔT = T_final - T_initial)

Formula

The relationship between heat energy (Q), mass (m), specific heat capacity (c), and change in temperature (ΔT) is given by the following formula:

Formula	Equation
Heat Energy (Q)	$Q = mc\Delta T$

Where:

• Q = Heat energy added (in Joules, J)
• m = Mass of the object (in kilograms, kg)
• c = Specific heat capacity of the material (in J/kg°C)
• ΔT = Change in temperature (in degrees Celsius, °C) or Kelvin, K)

Examples

Different materials have different specific heat capacities. For example:

• Water has a high specific heat capacity (approximately 4200 J/kg°C). This means a large amount of energy is needed to raise the temperature of water.
• Metals generally have lower specific heat capacities than water.

This difference in specific heat capacity explains why water is often used as a coolant in engines and other systems.

Practice Questions

1. A 2 kg block of iron is heated from 20°C to 50°C. The specific heat capacity of iron is 450 J/kg°C. Calculate the amount of heat energy required.
2. Explain why a metal spoon feels colder than a wooden spoon at room temperature, even if they are at the same temperature.