Question 1: Define a pure substance and give two examples.

Answer: A pure substance contains only one type of particle; examples include distilled water and pure aluminium.

Question 2: Explain why impurities in a sample can affect its boiling point.

Answer: Impurities disrupt the uniform structure, causing variations in boiling point, often increasing or broadening the boiling range.

Question 1: A sample of a mineral contains 45 grams of sulphur and 55 grams of total sample. Calculate the percentage purity of sulphur in the sample.

Answer: 81.82%

Question 2: If a solution is prepared by dissolving 5 grams of a pure substance in 95 grams of water, what percentage of the solution is the pure substance?

Answer: 5%

Question 1: Describe a basic procedure to test the purity of a sample of water using boiling point measurement.

Answer: Heat the water gradually and record the temperature at which it boils. A pure water sample boils at 100°C under standard pressure; deviations suggest impurities.

Question 2: Identify two safety precautions that must be taken when heating chemical samples in the laboratory.

Answer: Use heat-resistant containers and wear safety goggles to protect against splashes or breakage.

Question 1: A sample of copper sulphate was analysed, and the mass of pure copper sulphate was found to be 25 grams out of a total of 30 grams of the sample. Calculate the purity percentage of copper sulphate in the sample.

Answer: 83.33%

Question 2: A student measures the boiling point of a water sample and finds it to be 99°C. Discuss what this indicates about the purity of the sample and why.

Answer: The boiling point is slightly below 100°C, indicating the presence of impurities that lower the boiling point due to boiling point depression, thus suggesting the water is not pure.

Question 1: Explain why pharmaceutical companies must ensure their medicines are pure substances before distribution.

Answer: To ensure safety and efficacy; impurities can cause adverse effects or reduce the medicine's effectiveness.

Question 2: Describe how the process of distillation can be used to increase the purity of a liquid mixture.

Answer: Distillation involves heating the mixture so that the component with the lower boiling point vaporises first. The vapour is then condensed back into pure liquid, separating it from other components, thus increasing purity.