Heat Capacity

Definition:

Heat capacity is a measure of the amount of heat energy required to raise the temperature of a substance by a certain amount.

Formula:

 C=Q / ΔT  or Q= C ​. ΔT

Where:

• C is the heat capacity,
• Q is the heat energy absorbed or released,
• ΔT is the change in temperature.

Units: 

Heat capacity is typically measured in joules per degree Celsius (J/°C) or in calories per degree Celsius (cal/°C).

Key Points:

• Proportional to Mass: Heat capacity increases with the mass of the substance.
• Material Dependence: Different materials have different heat capacities due to their specific heat capacities.
• Phase Dependence: Heat capacity can vary depending on whether the substance is solid, liquid, or gas.

Specific Heat Capacity

Definition:

Specific heat capacity, often simply referred to as specific heat, is a physical property of a substance that measures how much heat energy is required to raise the temperature of a unit mass (usually one gram or one kilogram) of the substance by one degree Celsius (or one Kelvin).

Formula:

In mathematical terms, specific heat capacity (c)  is defined as:

Q = m ⋅ C ⋅ ΔT 

where, 

Q is the heat energy absorbed or released, 

m is the mass of the substance, 

C is the specific heat capacity, and

ΔT is the change in temperature.

Units:

The SI unit of specific heat capacity is joules per kilogram per degree Celsius (J/kg°C) or joules per gram per degree Celsius (J/g°C).

Explanation:

Specific heat capacity is a crucial parameter in thermodynamics and heat transfer calculations. It varies depending on the substance and can be affected by factors such as temperature and pressure. Substances with higher specific heat capacities require more heat energy to change their temperature compared to substances with lower specific heat capacities.

Example:

Imagine two metal objects, one made of aluminium and the other of copper, sitting side by side under the bright sun. Despite receiving the same amount of sunlight, you notice that the copper object becomes hotter faster than the aluminium one. This difference in temperature response is due to a property called specific heat capacity. 

In the case of our metal objects, copper has a lower specific heat capacity than aluminium, meaning it heats up more quickly. It’s like comparing two sponges: one absorbs water rapidly (low specific heat), while the other, though the same size, requires more water to cause a noticeable change (high specific heat). 

Specific heat capacity is a fundamental thermodynamic property that characterises the amount of heat energy required to raise the temperature of a unit mass of a substance by a certain amount.