Question 1: Define latent heat and explain its significance during phase changes in matter.

Answer: Latent heat is the heat energy required to change the state of a unit mass of a substance without changing its temperature. It is significant because it enables phase changes such as melting, freezing, boiling, and condensing.

Question 2: Describe what happens to the particles of a substance at the molecular level during the process of melting.

Answer: During melting, particles gain enough energy to overcome the forces holding them in a fixed position, changing from a solid to a liquid, with particles moving more freely.

Question 3: Which form of latent heat is involved when water turns into steam at 100°C?

Answer: Latent heat of vaporisation

Question 4: Fill in the blank: The amount of heat energy required to convert 1 kg of a substance from liquid to gas at its boiling point is called the __________.

Answer: latent heat of vaporisation

Question 1: A 0.5 kg block of ice at 0°C is melted completely. The specific latent heat of fusion of ice is 3.3×10^5 J/kg. Calculate the heat energy required to melt the ice.

Answer: 165000 J

Question 2: Calculate the energy required to convert 2 kg of water at 100°C into steam at the same temperature. Use the latent heat of vaporisation as 2.26×10^6 J/kg.

Answer: 4.52×10^6 J

Question 1: Describe a simple experiment to demonstrate the concept of latent heat during melting. Include the variables you would control and safety precautions.

Answer: An experiment could involve heating a known mass of ice in a controlled environment and measuring the time taken to melt at a constant temperature. Variables include initial ice temperature, heat source power, and insulation. Safety precautions include handling hot equipment carefully and avoiding spills.

Question 2: Explain how understanding latent heat is important in the design of refrigeration systems.

Answer: Refrigeration systems rely on phase changes, typically evaporation and condensation, which involve latent heat transfer. Knowledge of latent heat allows engineers to select appropriate working fluids and control energy efficiency, ensuring effective cooling with minimal energy loss.

Question 3: In industrial processes, why is it important to control the rate of heat transfer during phase changes?

Answer: Controlling the rate of heat transfer prevents rapid temperature changes that can cause structural damage, ensures uniform phase change, and improves energy efficiency in industrial operations.