Introduction to the particulate nature of matter - separating mixtures Flashcards
Can pure substances be separated?
Pure substances cannot be separated into individual constituents without a chemical reaction, which alters their physical properties.
Can mixtures be separated?
Mixtures can be separated into individual components that retain their respective physical properties.
What do separation techniques rely on?
There being a difference of some sort between the substances being separated, usually a physical property such as boiling point.
Describe filtration
- mixture is poured through a paper filter or other porous material
- separates an undissolved solid from liquid / solid mixture
- removes liquid, leaves solid
Describe dissolution (solvation)
- Mixture (of solids) is added to water or an organic solvent
- requires difference in solubility
- removes soluble substances, leaves insoluble substances
Describe crystallisation
- mixture is dissolved in hot water or organic solvent, solution cools down, forms crystals, isolated by filtration
- more soluble substances are removed, less soluble substances left
Describe evaporation
- mixture is heated up until one or more of its components vaporise
- removes volatile liquids, leaves solid(s) and / or non-volatile liquid(s)
Describe simple distillation
Solution is heated, liquid evaporates and passes through a condenser, cools & condenses and is collected in a beaker. Solid solute residue.
Describe fractional distillation
Separates two or more miscible liquids. Solution is heated to lowest boiling point, that liquid evaporates, passes through condenser, cools and condenses into liquid collected in a beaker. Other components are left behind, process repeats.
Describe paper chromatography
- Separates substances with different solubilites in a given solvent
- Mixture is placed on a piece of paper, end of paper is submerged in water / solvent; components move along paper by capillary action
- more soluble components move further, less soluble move slower / stay in place
