Unit C1: Atomic Structure - C1.3 Separating mixtures (Pages 8-9)

What is the definition of a mixture?

• A substance where elements have a fixed composition and are chemically bonded.

• Two or more substances (elements or compounds) that are not chemically combined together.

• A substance formed when chemical reactions are used to separate elements.

• A pure substance containing only one type of atom.

Which of the following is a key difference between a mixture and a compound?

• Mixtures have chemical bonds between their different substances, whereas compounds do not.

• Compounds must be separated by physical means, whereas mixtures require chemical reactions.

• Mixtures have no fixed composition, whereas the ratio of elements in a compound is fixed.

• Compounds are made of elements, but mixtures are not.

Filtration is a technique used to separate...

• two liquids that have different boiling points.

• a soluble solid from a liquid.

• two solids from each other.

• an insoluble substance from a solvent.

When filtering a mixture of sand and salt water, what is the scientific name for the sand that is left on the filter paper?

• The filtrate.

• The residue.

• The solvent.

• The distillate.

When filtering a mixture of sand and salt water, what is the scientific name for the salt solution that passes through the filter paper?

• The filtrate.

• The residue.

• The solvent.

• The compound.

Which separation technique is best used to obtain a sample of a pure, soluble solid (like salt) from its solution?

• Filtration.

• Simple distillation.

What is the purpose of simple distillation?

• To separate an insoluble solid from a liquid.

• To separate a solvent from a solution, allowing the solvent to be collected.

• To separate two solids from each other.

• To separate two miscible liquids.

In the apparatus for simple distillation, what is the function of the condenser?

• To heat the solution and turn the solvent into vapour.

• To cool the hot vapour and turn it back into a liquid.

• To measure the temperature of the vapour.

• To collect the final separated liquid.

Which physical property do separation techniques like filtration, crystallisation, and distillation rely on?

• The chemical reactivity of the substances.

• The colour of the substances.

• Differences in the physical properties of the substances, such as solubility or boiling point.

• The mass of the substances involved.

When obtaining salt crystals from a salt solution, why is the heating stopped when small crystals first appear?

• To prevent the salt from decomposing.

• To allow the rest of the water to evaporate slowly, forming good quality crystals.

• To prevent the water bath from boiling dry.

• Because the solution is now pure salt.