Question 1: Define internal energy in the context of the particle model of matter.

Answer: Internal energy is the total kinetic and potential energy stored within the particles of a substance due to their random motion and interactions.

Question 2: Explain how internal energy relates to the temperature of a substance.

Answer: As the internal energy increases, the temperature of the substance rises because the particles move faster, increasing their kinetic energy.

Question 3: What is the primary form of energy stored in a solid when it is heated?

Answer: Kinetic energy of the particles due to increased vibration.

Question 1: Describe what happens to the internal energy of water as it boils at 100°C.

Answer: The internal energy increases as heat is added, which supplies the energy needed for the particles to overcome forces and change from liquid to gas, involving latent heat.

Question 2: State what occurs to the internal energy of a substance during cooling.

Answer: The internal energy decreases as heat is lost, causing particles to slow down and the temperature to decrease.

Question 3: Identify the energy transfer process involved when a hot object cools down in a cooler environment.

Answer: Heat transfer by conduction, convection, or radiation from the hot object to the surroundings.

Question 1: A 2 kg block of aluminium is heated, increasing its internal energy by 6000 J. If the specific heat capacity of aluminium is 900 J/kg°C, calculate the change in temperature of the block.

Answer: ΔT = Q / (m × c) = 6000 J / (2 kg × 900 J/kg°C) = 3.33°C

Question 2: A substance absorbs 2500 J of heat, and its temperature increases by 5°C. If the mass of the substance is 0.5 kg and its specific heat capacity is 1000 J/kg°C, verify this heat transfer value.

Answer: Q = m × c × ΔT = 0.5 kg × 1000 J/kg°C × 5°C = 2500 J (which matches the given heat absorbed)

Question 1: Describe a simple experiment to demonstrate the increase in internal energy when a substance is heated.

Answer: Heat a solid such as a metal rod using a controlled heat source, measure its temperature before and after heating with a thermometer, and observe the increase in temperature indicating increased internal energy. Ensure safety precautions such as wearing protective gloves and eye protection are followed.

Question 2: List three safety precautions that should be observed during experiments involving heating substances.

Answer: Use heat-resistant gloves, wear safety goggles, and ensure proper ventilation in the experiment area.

Question 1: A pressure cooker increases the internal energy of water to boil it faster. Explain how increasing pressure affects internal energy and boiling point.

Answer: Increasing pressure raises the boiling point, meaning more internal energy is required for water to boil at higher pressure, thus increasing the rate of energy transfer and cooking efficiency.

Question 2: In which industry or technology is understanding internal energy crucial for improving efficiency or safety? Provide a brief explanation.

Answer: In thermal power plants, understanding internal energy helps optimise heat transfer, improve efficiency, and prevent accidents caused by overheating or pressure build-up.