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 free to move, allowing it to flow; a gas has particles far apart and move freely, filling the container.

Question 2: Explain why gases are compressible while solids and liquids are not.

Answer: Gases are compressible because their particles are far apart with lots of space, so applying pressure reduces the volume; solids and liquids have particles closely packed, leaving little space to compress.

Question 1: Describe the key variables that need to be controlled when investigating the rate of diffusion of a gas in a laboratory experiment.

Answer: Variables include temperature, pressure, particle size, and concentration gradient, as these affect the rate at which gases diffuse.

Question 2: List two safety precautions that should be taken when heating gases in a laboratory experiment.

Answer: Use heat-resistant gloves and ensure proper ventilation to avoid inhalation of harmful gases.

Question 1: A sample of gas has a volume of 2.5 litres at a temperature of 300 K and a pressure of 1 atmosphere. Using the ideal gas law (PV = nRT), calculate the number of moles of gas present. (R = 0.0821 L·atm/(mol·K))

Answer: n = PV / RT = (1 atm)(2.5 L) / (0.0821 L·atm/(mol·K))(300 K) ≈ 0.101 mol

Question 2: Calculate the density of a gas sample if 0.2 mol occupies a volume of 5 litres at 300 K. (Use molar mass of the gas as 28 g/mol).

Answer: Density = mass/volume = (0.2 mol)(28 g/mol) / 5 L = 5.6 g / 5 L = 1.12 g/L

Question 1: Explain how the understanding of gases is utilised in the design of scuba diving equipment.

Answer: Knowledge of gas laws helps in designing tanks that can withstand high pressure, ensuring safe compression and decompression of breathing gases for divers.

Question 2: Identify a technological application that relies on the properties of gases and describe its function.

Answer: Internal combustion engines rely on the rapid expansion of gases during combustion to produce mechanical work.

Question 1: Discuss the differences in the energy levels of particles in solids, liquids, and gases. How does this relate to their physical properties?

Answer: Particles in solids have the lowest energy levels, mostly vibrating in fixed positions, which accounts for their rigidity and incompressibility. In liquids, particles have higher energy, allowing them to slide past each other, giving fluids their ability to flow. Gases have the highest energy, with particles moving freely at high speeds, which explains their compressibility and ability to fill containers. These energy differences directly influence their physical properties such as shape, volume, and response to pressure.