Separating Mixtures
Use knowledge of solids, liquids, and gases to decide how mixtures might be separated through filtering, sieving, and evaporating
What a learner can do afterwards
- Choose a separation method using particle size and solubility: sieve differently sized solids, filter undissolved solids from water, or evaporate water to recover dissolved salt
- Describe a plan to recover sand and salt from sand mixed into salty water, and explain that evaporation does not collect the water
- Explain why each method works based on the properties of the materials
1 · Read
A mixture contains materials that can be separated using their different properties. A sieve separates dry solids if its holes let smaller pieces through but hold larger ones. Suitable filter paper traps undissolved sand grains while water passes through. Dissolved salt particles pass through ordinary filter paper with water. Evaporating water can recover the salt.
Mia has sand mixed into salty water. Filter paper in a funnel traps the sand. Water and dissolved salt pass into a dish below. She leaves the dish somewhere warm. Water evaporates into the air, leaving salt behind. If gravel were present too, she could first sieve it out using holes that hold gravel but let sand and water through.
Water can evaporate without boiling. A shallow dish gives water a large surface from which to escape into the air. If water remains, some salt may still be dissolved, even when the liquid looks clear. Ordinary sieving and filtering cannot trap that dissolved salt. Evaporation is one way to recover it. Heating speeds evaporation, but heating experiments need adult supervision.
Match holes to solid pieces. Filter undissolved sand. Evaporate water to recover dissolved salt; the water escapes into the air.
Lesson, questions and flashcards written for this dataset.
Reading and flashcards written for this dataset.
More to read
Keep track of each material
Plan where each material will go before starting a separation. For a mixture containing gravel, sand and salt solution, you need places to collect the gravel, sand and salt.
Choose sieve holes that hold gravel but let sand and liquid through. Filter the liquid next. The sand stays on the paper, but dissolved salt travels with the water.
Evaporating that water leaves salt. The water escapes into the air, so this plan does not collect every material. Clear liquid below a filter is not proof of pure water.
2 · Watch
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Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.