Lesson focus: mixtureTwo or more substances mixed together but not chemically joined, like sand and salt. are separated by sequences exploiting physical-property differences.
Design a complete separationGetting the different substances in a mixture apart from each other. route and identify where each product goes.
Build on earlier learning
Chemical formulae and balancingDistinguish physical separation of substances from chemical rearrangement.
You will be successful when you can…
- Distinguish mixtures from compounds.
- Choose methods from physical properties.
- Sequence filtration and crystallisation/distillation.
- Identify residue, filtrate and recovered products.
Words that carry the science
- mixture
- Substances together without chemical bonding between them.
- separation
- Process recovering components using property differences.
- solubility
- Maximum amount dissolving under stated conditions.
- boiling point
- Temperature of boiling at a stated pressure.
- purity
- Extent to which a sample contains one substance.
Choose each method from a property and desired product
01Start with the goal
If sand, salt and water are mixed, decide whether salt, water or both must be recovered. The route depends on desired products.
02Use a sequence
Filter insoluble sand. Crystallise the salt solution to recover salt, or distil it to collect water while salt remains.
03Check rather than assume purity
Dry and weigh recovered solids, compare melting/boiling ranges or repeat separationGetting the different substances in a mixture apart from each other.. Each check has limitations and uncertainty.
Recover all three components
Separate sand, salt and water.
- Filter: sand remains as residue; salt solution is filtrate.
- Wash and dry sand to remove adhering salt solution.
- Distil the filtrate: collect water distillate.
- Concentrate/cool residue solution and dry salt crystals.
How to make the reasoning visible: Name the destination of every component.
Method decision table
Match property to method.
| Mixture | Property difference | Method | Product location |
|---|---|---|---|
| Sand + water | Particle size/insolubility | Filtration | Sand residue |
| Salt + water | Volatility | Distillation | Water distillate |
| Ink dyes | Surface/solvent attraction | Chromatography | Separate spots |
| Iron + sulfur | Magnetism | Magnet | Iron attracted |
Why is one method insufficient for salt, sand and water?
How can washing improve recovered sand?
Describe how you would get pure salt from a mixture of salt, sand and water.
Check your understanding
Answer from memory, then check against the suggested answer.
What is mixture?
What is separation?
What is solubility?
Which method separates an insoluble solid from a liquid?
Which method separates the dyes in ink?
You need salt but not water. Which route follows filtration?
Suggest a purity check for recovered water and one limitation.
Why can a magnet separate iron from sulfur in a mixture, but not from iron sulfide?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
Describe how to obtain dry salt and dry sand from a mixture of salt, sand and water.
(5)Total for this question: 5 marks
Command word: Follow both products to the end; “filter it” is not a complete route.