Flashcards in Topic 2- States of Matter and Mixtures Deck (36):
Sting forces of attraction
Definite shape and volume
Don’t have much kinetic energy
Vibrate- the hotter the solid becomes the more the particles vibrate (causing solids to expand slightly when heated)
Some force of attraction
Free to move past each other (random motion) but tend to stick together
Don’t keep a definite shape
Keep the same volume
More energy than solid state but less energy than gas state
The hotter the liquid, the faster they move (more energy)
No force of attraction
Free to move (random motion), travel in straight lines and only interact when they collide
Don’t keep a definite shape or volume
When the particles bounce of the walls of container they exert a pressure on the walls
More energy than liquid and solid states
Hotter they get, the faster they move because they have more energy meaning pressure increases
Chemical changes happen...
During chemical reactions, when bonds between atoms break and the atoms change places.
The atoms from the substances you start off with (the reactants) are rearranged to form different substances (the products)
Hard to reverse (compared to physical changes)
Contain only one element or compound
A mixture is...
More than one compound or different elements that aren’t all part of a single compound
Purity can be tested for by using...
Melting points and boiling points
Every pure substance has a specific, sharp melting point and boiling point
Impure substance will...
Melt or boil gradually over a range of temperatures
Simple distillation is used to...
Separate out solutions
Fractional distillation is used to...
Separate a mixture of liquids
Simple distillation method...
1. Heat distillation flask with sample of sea water in
2. The part of the solution with the lowest boiling point will evaporate first- the water
3. The water vapour passes into the condenser and cools and condenses
4. Water is collected in the beaker and salt left in the flask at the start
Fractional distillation method...
SEE REVISION GUIDE (IMPORTANT)
Filtration is used to...
Separate an insoluble solid from a liquid
Filter paper in a funnel, the liquid runs through the paper and the residue left behind is the solid
Crystallisation is used to...
Separate a solvable solid from a solution
1. Heat an evaporating dish containing the solution (the solution will get more concentrated as the water evaporates)
2. When you see crystals or when some water has evaporated, leave the solution to cool
3. Filter the crystals out of the solution and leave them to dry
Chromatography is used to...
Separate a mixture of soluble substances and identify them
A mobile phase...
Where the molecules can move
This is always a liquid or gas
A stationary phase...
Where the molecules can’t move
This can be a solid or a really thick liquid
The components in the mixture ... as the mobile phase moves over the stationary phase- they all end up in ... in the stationary phase
This is because...
Each chemical in the mixture will spend different amounts of time dissolved in the mobile phase and stuck to the stationary phase
How fast a chemical moves through the stationary phase depends on...
How it distributes itself between the two phases
In paper chromatography, the stationary phase is...
A piece of filter paper
In paper chromatography the mobile phase is...
In the solvent
Method for paper chromatography
1. Draw a baseline in pencil at the bottom of the paper and then put a spot of the mixture in this line.
2. Then place the paper into the solvent but not covering the spot of mixture.
3. Put a watch glass on top of the beaker to stop any solvent evaporating away.
4. Remove the paper from the beaker before the solvent reaches the top, mark the distance the solvent has moved in pencil - the solvent front
The amount of time the molecules spend in each phase depends on two things...
1. How soluble they are in the solvent
2. How attracted they are to the stationary phase
Molecules with a higher solubility in the solvent (less attracted to the paper) will...
Spend more time in the mobile phase than the stationary
Will be carried further up the paper
If you have chemicals in you mixture which are colourless (eg.amino acid) you...
Spray the chromatogram with a locating agent
Distance travelled by solute / distance travelled by solvent
Uses of chromatography...
Chemist run pure substances next to mixtures to see what components to mixture can be identified to
Also to see where a substance is pure or not- a pure substance won’t separate into more than one spot
You can combine separation techniques to analyse mixtures
Eg. You could use a mixture of simple distillation and chromatography to analyse the composition of ink
From lakes, river and reservoirs
In much of England and Wales this resource starts to run dry during the summer months
From aquifers (rocks that trap water underground)
In parts of South East England where surface water is very limited , as much as 70% of domestic water supply comes from ground water
From water that’s been contaminated by human processes eg.as a by product from some industrial processes
Treating waste water is preferable to disposing of water , which can turn out to be polluting
How easy the waste water is to treat depends on the level of contaminants in it
Purification of water- filtration
A wire mesh screens out large twigs ect.
And then gravel and sand beds filter out the rest
Purification of water- sedimentation
Iron sulfate or aluminium sulfate is added to the water, which makes fine particles clump together and settle at the bottom
Purification of water- chlorination
Chlorine gas is bubbles through to kill harmful bacteria and other microbes
You can get potable water from sea water by...
Distillation eg. In dry countries like Kuwait
Requires lots of energy