CC2: States Of Matter And Mixtures Flashcards
Describe a solid
Low energy/Small vibrations/rigid lattice structure/strong forces of attraction between particles/definite shape and volume/when heat applied it vibrates more, bonds begin to loosen/expand slightly when heated
Describe a liquid
Bonds less strong/free to move and roll over each other/expands when heated/vibrates more than solids/higher energy/takes shape of container/fixed volume/the hotter the faster the particles move
Describe a gas
High energy/no forces of attraction between them/fill up any container/ no fixed shape or volume/can be compressed/when heat is applied it can have higher pressure or expand
Melting
When heat is applied to a solid and the particles vibrate, weakening them and making the solid expand. At a certain temperature the particles can break free from their positions.
Boiling
When more heat is applied and eventually the particles’ bonds break free completely and the liquid turns to a high energy gas
Desposition
From gas to a solid. Requires lots of energy
Condensation
Gas to liquid- needs to cool and lose heat energy
Evaporation
Liquid to gas
Sublimation
Solid to gas- requires lots of energy
What is a physical reaction?
A change in state, often reversible
What is a chemical reaction?
Change in structure- when atoms swap round and reactants can be reacted to for, different products. This can often be hard to reverse or irreversible
What is a homogenous mixture?
A mixture where only one thing can be seen eg seawater
What is a heterogeneous mixture?
A mixture where many components to the mixture can be seen eg sand in water
How can we separate homogenous mixtures?
Simple/fractional distillation or crystallisation
How can we separate heterogenous mixtures?
Through filtration
Then go on to distillation etc
What is the meaning of pure?
Containing one single element or compound throughout the structure eg pure gold is just gold atoms
How can we test if a substance is pure?
Melt it: if it has a melting point range it is an impure mixture, if it has one sharp melting point it is pure eg pure water has a boiling point of 100 degrees c
Give an example of simple distillation
Saltwater.
Heat it. Water will evaporate at 100 degrees c and rise as a vapour and go down the cooling tube with cold water running through it which will condense the vapour which will run into a flask.
Leave the salt to dry and it will crystallise.
Fractional distillation
Used when the range of boiling points in the mixture are very similar.
They separate off in the fractionating column- bigger molecules with higher boiling points condense and leave at the bottom which is hotter and the smaller molecules with lower boiling points leave and condense at the cool top of the column.
Give two examples of fractional distillation
Crude oil
Air
How do you fractionally distill air?
Liquefaction and fractional distillation
Cool to -200 for all gases to be liquified and slowly heat them to turn into gas and condense them again
Filtration
Using filter paper to separate insoluble particles from liquid
Crystallisation
Separates soluble solid from a solution
How to crystallise a product?
Heat your solution in an evaporating dish. The solvent should evaporate and the solution will get more concentrated.
Crystals may start to form when the water has gone.
The salt should form an insoluble crystal solid. You can filter them out and leave them to dry.
Mobile phase
The solvent- either liquid or gas
Stationary phase
Where molecules can’t move eg paper in paper chromatography- either a solid or a thick liquid
Describe paper chromatography
Stationary phase- piece of paper
Mobile phase- water/ethanol
Draw line on the bottom of the paper with pencil so pen ink isn’t mixed
Put a spot of mixture onto the line- not under as it could dissolve in the solvent straight away.
Put the paper in the mobile phase UNDER the line as otherwise the mixture could dissolve
The solvent will start to move up the paper and the chemicals in the mixture will separate and move up the paper
What does it mean if a spot stays on the line?
It is insoluble
What happens with molecules with higher solubility?
Spend more time in the mobile phase and carried further up paper
What are 2 factors for a long time spent on each phase?
How attracted to the stationary phase the chemicals are
How soluble they are in the solvent
Rf Value
Distance travelled by solute/distance travelled by solvent
Always under 1
Locating agent
Spray to find colourless solutes in the mixture eg amino acids
What is a standard reference material?
A pure substance to check identity of mixture’s components (basically check it there are any same in it eg black ink next to black ink u get me)
What can u use chromatography for?
Separating mixtures Checking solubility (won't move if insoluble) Checking purity (won't separate if pure)
3 sources of water
Surface water
Ground water
Waste water
Surface water
Lakes, rivers, reservoirs- not very pure, needs to be treated well
Ground water
From aquifers (rocks in ground that trap water)- relatively pure
Waste water
By-product of industrial processes etc
Needs to be treated very well as it was contaminated
3 steps to water treatment
Filtration
Sedimentation
Chlorination
Filtration
Filter water through metal mesh to get rid of large insoluble sediment eg rocks and twigs
Sedimentation
Use iron sulphate or aluminium sulphate to make fine sediment clump together which can then be filtered out
Chlorination
Bubble chlorine gas through the water which kills harmful microbes
Potable
Fit to drink
How else can potable water be obtained?
Distilling sea water through simple distillation
What kind of water is ideal to use in a scientific experiment?
Distilled/deionised water.
This is because all ions like calcium and iron and copper irons are not in this water and therefore cannot interfere with results.
When is simple distillation used?
When the mixture has two very different boiling points
When is fractional distillation used?
When the boiling point range is very close/ has similar boiling points
What is fractional distillation performed in?
A fractionating column
Differences between pure substances and mixtures
Pure- one m/b point
Mixture- m/b point range
Pure- one single element/compound throughout
Mixture- a mixture of elements/compounds
