Question 1: Define a solid, a liquid, and a gas in terms of their particle arrangement and movement.

Answer: A solid has particles tightly packed in a fixed structure with limited movement; a liquid has particles close together but can move past each other, allowing it to flow; a gas has particles far apart and move freely at high speeds.

Question 2: Explain how the particles in a solid, liquid, and gas behave when heated.

Answer: Particles in a solid vibrate more vigorously when heated, but their positions remain fixed. In liquids, particles move faster and slide past each other. In gases, particles gain kinetic energy, move more rapidly, and collide more forcefully.

Question 3: Multiple Choice: Which of the following best describes the particle arrangement in a gas?

Answer: Particles are far apart and move freely.

Question 1: Describe what happens at the particle level during melting and boiling.

Answer: During melting, particles absorb energy, vibrate more vigorously, and overcome the forces holding them in a fixed position, turning a solid into a liquid. During boiling, particles gain enough energy to overcome intermolecular forces entirely and become a gas.

Question 2: Fill in the blank: The process where a gas turns directly into a solid is called __________.

Answer: deposition

Question 3: Calculate the energy required to convert 2 kg of water at 100°C to steam at 100°C. (Specific latent heat of vaporisation of water = 2.26 x 10^6 J/kg)

Answer: Q = m x L = 2 kg x 2.26 x 10^6 J/kg = 4.52 x 10^6 Joules

Question 1: Identify two safety precautions when heating substances to observe state changes in the laboratory.

Answer: Use heat-resistant gloves and safety goggles; perform heating in a well-ventilated area and avoid heating sealed containers to prevent pressure build-up.

Question 2: A sample of sulphur is heated and changes directly from a solid to a gas. Explain this process and name it.

Answer: This process is called sublimation. When sulphur is heated, it absorbs energy, and its particles gain enough kinetic energy to overcome intermolecular forces directly from a solid to a gas without passing through the liquid phase.

Question 3: Describe how the understanding of particle behaviour in gases is important for industries such as aerospace engineering.

Answer: In aerospace engineering, knowledge of particle behaviour in gases helps in designing propulsion systems, understanding aerodynamics, and predicting how gases expand and exert pressure. This understanding ensures safe, efficient, and effective aircraft and spacecraft design under different atmospheric conditions.