(a) State three reasons why air is classified as a mixture. (b) List two methods that can be used to separate a mixture of iodine crystals and iron filings.

Answer Details

(a) Air is classified as a mixture because:

• Its components can be separated by physical means (fractional distillation of liquid air).
• Its components retain their own individual properties.
• Its composition is variable (the proportions are not fixed) and the components are not combined in any fixed ratio, and no chemical reaction or energy change occurs when they are together.

(b) A mixture of iodine crystals and iron filings can be separated by:

• Using a magnet to remove the iron filings (magnetic separation).
• Sublimation - warming the mixture so the iodine sublimes and is collected, leaving the iron filings behind.