Latent Heat-Chapter 2

Q: What is latent heat?

A: The energy required to change a substance's phase (solid ↔ liquid ↔ gas) without changing its temperature.

Q: What is the formula for latent heat?

A: Q = mL, where Q = heat absorbed or emitted, m = mass of the substance, L = specific latent heat

Q: What are the different types of latent heat?

A: Latent heat of fusion (solid to liquid), latent heat of vaporization (liquid to gas), and latent heat of condensation (gas to liquid)

Q: How do you calculate the specific latent heat when heat and mass are known?

A: L = Q/m

Q: What key characteristic distinguishes latent heat from other forms of heat transfer?

A: Latent heat is independent of temperature change during phase transition.

Q: What is the principle of mixtures?

A: The principle that heat lost by one substance equals heat gained by another in a closed system, used to determine unknown specific heats or temperatures in thermal equilibrium.

Q: How is the specific heat of metals calculated in calorimetry experiments?

A: By measuring temperature changes and applying the principle of mixtures, equating heat lost by one substance with heat gained by another.

Q: What is the difference between boiling and evaporation?

A: Boiling occurs throughout the liquid at a specific temperature, while evaporation happens at the surface at any temperature and causes cooling effects.

Kinetic Theory of Gases

Q: What does the Kinetic Theory of Gases describe?

A: Five fundamental postulates explaining how gas molecules behave and interact, including assumptions about molecular motion, collisions, and energy distribution.

Q: How are heat and temperature related to molecular motion?

A: Temperature is a measure of average kinetic energy of molecules, while heat represents the total energy transferred due to temperature differences.

Q: What is a calorimeter used for?

A: To measure specific heat capacities by tracking heat transfer between substances.

Q: How does the molecular basis explain temperature?

A: Temperature is directly related to the average kinetic energy of molecules - faster moving molecules result in higher temperatures.

Q: What happens to molecules during a phase change?

A: They gain or lose energy while maintaining the same temperature, changing their arrangement and intermolecular forces.

Q: How would you calculate the heat required to melt 5kg of ice at 0°C? (Latent heat of fusion for ice = 334,000 J/kg)

A: Q = mL = 5 kg × 334,000 J/kg = 1,670,000 J or 1,670 kJ

Q: What is the relationship between heat lost and gained in a mixture problem?

A: Heat lost by one substance equals heat gained by another (Heat lost + Heat gained = 0)

Q: What is latent heat?

A: The energy required to change a substance's phase (solid ↔ liquid ↔ gas) without changing its temperature.

Q: What is the formula for latent heat?

A: Q = mL, where Q = heat absorbed or emitted, m = mass of the substance, L = specific latent heat

Q: What are the different types of latent heat?

A: Latent heat of fusion (solid to liquid), latent heat of vaporization (liquid to gas), and latent heat of condensation (gas to liquid)

Q: How do you calculate the specific latent heat when heat and mass are known?

A: L = Q/m

Q: What key characteristic distinguishes latent heat from other forms of heat transfer?

A: Latent heat is independent of temperature change during phase transition.

Q: What is the principle of mixtures?

A: The principle that heat lost by one substance equals heat gained by another in a closed system, used to determine unknown specific heats or temperatures in thermal equilibrium.

Q: How is the specific heat of metals calculated in calorimetry experiments?

A: By measuring temperature changes and applying the principle of mixtures, equating heat lost by one substance with heat gained by another.

Q: What is the difference between boiling and evaporation?

A: Boiling occurs throughout the liquid at a specific temperature, while evaporation happens at the surface at any temperature and causes cooling effects.

Kinetic Theory of Gases

Q: What does the Kinetic Theory of Gases describe?

A: Five fundamental postulates explaining how gas molecules behave and interact, including assumptions about molecular motion, collisions, and energy distribution.

Q: How are heat and temperature related to molecular motion?

A: Temperature is a measure of average kinetic energy of molecules, while heat represents the total energy transferred due to temperature differences.

Q: What is a calorimeter used for?

A: To measure specific heat capacities by tracking heat transfer between substances.

Q: How does the molecular basis explain temperature?

A: Temperature is directly related to the average kinetic energy of molecules - faster moving molecules result in higher temperatures.

Q: What happens to molecules during a phase change?

A: They gain or lose energy while maintaining the same temperature, changing their arrangement and intermolecular forces.

Q: How would you calculate the heat required to melt 5kg of ice at 0°C? (Latent heat of fusion for ice = 334,000 J/kg)

A: Q = mL = 5 kg × 334,000 J/kg = 1,670,000 J or 1,670 kJ

Q: What is the relationship between heat lost and gained in a mixture problem?

A: Heat lost by one substance equals heat gained by another (Heat lost + Heat gained = 0)