Question 1: What is latent heat, and how does it differ from sensible heat?

Answer: Latent heat is the heat absorbed or released during a phase change without changing temperature. Unlike sensible heat, which changes temperature, latent heat is involved in changing the state of a substance.

Question 2: Explain why the temperature of a substance remains constant during a phase change when heat is added or removed.

Answer: The temperature remains constant because the heat energy is used to break or form bonds between particles during the phase change, not to increase temperature.

Question 1: Calculate the amount of heat required to convert 3 kg of ice at 0°C into water at 0°C. Use the latent heat of fusion for ice as 334 kJ/kg.

Answer: Q = mass × latent heat = 3 kg × 334 kJ/kg = 1002 kJ

Question 2: A piece of sulfur undergoes sublimation, changing directly from solid to gas. If 0.5 kg of sulfur sublimates, requiring 250 kJ of energy, what is the latent heat of sublimation for sulfur?

Answer: L = Q / mass = 250 kJ / 0.5 kg = 500 kJ/kg

Question 1: Outline the steps involved in an experiment to determine the latent heat of vaporization of water. Mention the variables that need to be controlled and safety precautions to consider.

Answer: The experiment involves heating a known mass of water until it boils and measuring the heat supplied. Variables to control include the mass of water, initial temperature, and heating rate. Safety precautions include using a heat-resistant container, avoiding steam burns, and wearing protective gear.

Question 1: A 2 kg block of ice at -10°C absorbs 4200 kJ of heat to become water at 20°C. Given the specific heat capacity of ice is 2.1 J/g°C and of water is 4.2 J/g°C, and the latent heat of fusion is 334 J/g, analyze the data to determine how much heat was used for each stage (warming ice, melting, warming water).

Answer: Heat to warm ice: 2,100 J/g × 10°C = 21,000 J; to melt ice: 334 J/g × 2000 g = 668,000 J; to warm water: 4,200 J/g × 20°C = 84,000 J; total: 21,000 + 668,000 + 84,000 = 773,000 J (or 773 kJ). The total heat supplied exceeds this, indicating extra heat for other energy exchanges or measurement errors.

Question 1: Describe how the concept of latent heat is used in the design of a refrigerator or air conditioner.

Answer: Refrigerators and air conditioners use the principles of latent heat during the evaporation and condensation of refrigerants to transfer heat away from the interior, cooling the space efficiently.

Question 2: Explain why understanding latent heat is important in the energy sector, particularly in power plants that use steam turbines.

Answer: Understanding latent heat allows engineers to optimize the efficiency of steam turbines by controlling the phase change of water into steam. Managing latent heat helps in designing systems that maximize energy transfer while minimizing energy loss during phase changes.