Short Answer

Heat capacity is the amount of heat energy required to raise the temperature of a substance by 1°C (or 1 K). It depends on the mass and nature of the substance.

For example, heating 1 kg of water by 1°C requires 4186 J of energy. Heat capacity is different for each substance because it depends on how much energy is needed to increase the kinetic energy of its particles.

Detailed Explanation

Heat Capacity

Heat capacity is a physical property that describes the ability of a substance to store heat. It is defined as the ratio of the amount of heat supplied to the resulting temperature rise:

Where:

•  = heat capacity (J/°C or J/K)
•  = heat energy supplied (Joules)
•  = temperature change (°C or K)

Heat capacity tells us how much energy is needed to increase the temperature of a material. A high heat capacity means the substance can absorb more heat without a large rise in temperature.

1. Types of Heat Capacity
2. Specific Heat Capacity

• Heat capacity per unit mass.
• Formula:
• Units: J/(kg·°C) or J/(kg·K)
• Example: Water has a high specific heat capacity (4186 J/kg·°C), meaning it requires more energy to increase its temperature.

1. Molar Heat Capacity

• Heat capacity per mole of substance.
• Formula:
• Units: J/(mol·°C) or J/(mol·K)
• Used for gases, solids, and liquids in chemistry calculations.

2. Factors Affecting Heat Capacity

• Mass: Larger mass → higher heat capacity.
• Nature of substance: Substances with stronger intermolecular bonds or more atoms per molecule generally have higher heat capacity.
• Phase: Heat capacity varies with solid, liquid, and gas.
• Temperature: Slight variations may occur with increasing temperature.

For example:

• Metals like iron have lower specific heat (~450 J/kg·°C) compared to water (~4186 J/kg·°C).
• Water can absorb a lot of heat with a small temperature change.

3. Significance of Heat Capacity

• Climate and Environment: Water bodies regulate temperature due to high heat capacity.
• Cooking: High heat capacity of water makes it efficient for boiling.
• Industrial Applications: Design of heating/cooling systems, engines, and chemical reactors relies on knowledge of heat capacity.
• Scientific Calculations: Thermodynamics and calorimetry use heat capacity to measure energy changes.

4. Measurement of Heat Capacity

Heat capacity is measured experimentally using calorimetry:

1. Heat a substance with known mass.
2. Measure the temperature rise.
3. Use the formula .

For specific heat:

• Example: Heating 100 g of water by 10°C:

This shows that heat capacity helps quantify energy needed for temperature changes.

5. Heat Capacity and Energy Storage

Heat capacity explains why some materials heat up slowly and others quickly:

• High heat capacity → absorbs more energy for the same temperature rise.
• Low heat capacity → temperature rises quickly for the same energy.

Example:

• Sand heats up faster than water on a sunny day because water has higher heat capacity.
• Ocean moderates coastal climate due to its high heat capacity.

Conclusion

Heat capacity is the measure of energy a substance can absorb to raise its temperature by 1°C or 1 K. It depends on the mass, chemical nature, and phase of the substance. Heat capacity plays a key role in everyday life, climate regulation, industrial processes, and thermodynamic calculations. Understanding it helps predict how substances respond to heat and energy changes.