Topic 2 Flashcards
What is a mixture
2 or more elements or compounds which aren’t chemically combined together
What is a pure substance
A single element or compound not mixed with any other substance
How can you usually tell whether a substsnce is mixed or pure?
Pure substances normally have fixed boiling points
Mixed substances melt over a range of substances
What is simple distillation
Used to separate a pure liquid from a
mixture
Works when liquids have different boiling points
For example - ethanol with evaportate first causing it to turn into a gas and condense in the condenser and is deposited in a flask
How do you doFractional distillation
Used to separate crude oil
Oil is heated and oil evaporates and condenses at many different temperatures
Pil has many hydrocarbons - which can be separated into fractions
Fractional column is used continuously as oil is piped in
Oil is evaporated and various fractions are tapped off at the different levels they condense
The fractions can be processed to produce fuel
Why and how do we use Crystallisation
If you wanted yo remove a soluble salt from liquid that it’s dissolved in
Heat solution in open container allowing solvevent to evaporate
Allow solution to cool
Solid comes out of solution and crystals will start to grow which can be collected and allowed to dry
Filtration
If you have produced a precipitate (insoluble salt) and want it removed from a it from the salt solution
Filter solution through filter paper
Leaving precipitate on the filter paper and solution in a container
What is paper chromatography used for
To separate soluble ( dissolved) substances in a solution
Why is pencil used in paper chromatography
It’s insoluble and won’t travel up paper
What will happen if substance is unpure in paper chromatography
There will be more than one dot on the paper
How do you find out how soluble something is in paper chromatography
The more soluble a substance is = the further up its moved up the chromatography paper
What is the stationary phase of chromatography
The paper
Whats the mobile phase of chromatography
Solvent ( the pen)
What is potable water and what are the conditions for it
Potable water = water suitable for drinking
Low levels of microbes
Low levels of contaminating substances
Not the same as pure water but still safe
How do you make waste and ground water potable step by step
Sedimentation - large insoluble particles sink to bottom of water
Filtration- water is filtered through sand which removes small insoluble particles
Chlorination- chlorine is put through water to kill microbes
