Separation of Substances
This chapter explains various methods of separating components of mixtures including handpicking, threshing, winnowing, sieving, sedimentation, decantation, filtration, evaporation, and condensation.
Quick Revision: Separation of Substances
- Handpicking: Manual separation of larger impurities like stones from grains.
- Threshing: Beating stalks to separate grain seeds from stalks.
- Winnowing: Using wind to separate lighter husk from heavier grains.
- Sieving: Separating particles of different sizes using a sieve.
- Sedimentation: Heavier insoluble solids settle down when mixture is allowed to stand.
- Decantation: Pouring out liquid without disturbing settled sediment.
- Filtration: Using a filter (strainer, cloth, filter paper) to separate solids from liquids.
- Evaporation: Conversion of water into water vapour by heating.
- Condensation: Conversion of water vapour into liquid upon cooling.
- Saturated Solution: A solution that cannot dissolve more of a substance at a given temperature.
- Loading: Adding alum to muddy water to make impurities settle faster.
Chapter Summary: Separation of Substances
We separate substances from mixtures for various reasons: to remove harmful or non-useful components, to obtain useful components, or to separate two useful components. Different separation methods are used based on the properties of the components.
Handpicking is used for large impurities. Threshing separates grains from stalks. Winnowing uses wind to separate lighter husk from heavier grains. Sieving separates particles of different sizes. Sedimentation and decantation separate insoluble solids from liquids by allowing settling and pouring off the liquid. Filtration uses a porous filter to separate solids from liquids. Evaporation converts water to vapour, leaving behind dissolved solids. Condensation converts vapour back to liquid. A saturated solution cannot dissolve more solute at a given temperature; heating can increase solubility.
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