Chapter 15: Thermal Energy and Heat

Heat Capacity (C)

The amount of thermal energy required to raise the temperature of an entire object by 1 °C or 1 K.

Specific Heat Capacity (c)

The amount of thermal energy required to raise the temperature of 1 gram of a substance by 1 °C or 1 K.

Thermal Equilibrium

The state in which two objects in thermal contact no longer exchange energy.

Calorimetry

The measurement of thermal energy transfer between substances during physical or chemical changes.

Heat Capacity and Specific Heat

• Relationship between heat (Q), mass (m), specific heat (c), and temperature change (ΔT): $Q=m\times c\times \mathrm{\Delta T}$
• Heat capacity is specific to the entire object, while specific heat is specific to the material.
• Calorimeters are insulated containers used to measure energy transfer during reactions.

Factors Affecting Heat Transfer

• Mass: Larger masses require more energy to achieve the same temperature change.
• Material: Different materials have unique specific heat capacities.
• Temperature Difference: Greater temperature differences increase the rate of heat transfer.

Applications of Specific Heat

• Water's high specific heat moderates Earth's climate by storing and releasing thermal energy.
• Metal's low specific heat makes it efficient for cooking utensils.
• Heat capacity is critical in engineering to design materials that can withstand thermal stresses.

Questions for Students

1. Define heat capacity and specific heat capacity. How are they different?
2. Write the formula for thermal energy transfer and explain each term.
3. Why is water's high specific heat important for the environment?
4. How does mass affect the amount of energy needed for a temperature change?
5. A 2 kg aluminum block (c = 0.897 J/g⋅°C) is heated from 20 °C to 100 °C. Calculate the energy required.