Topic 2 - States of matter and mixtures Flashcards
Describe solids particles
regular, close
move around eachother
Describe liquids particles
fits into the space
random,close
move around each other
Describe gasses particles
random, far apart
fast in all direction
Gas -> solid
deposition
Gas -> liquid
condensing
liquid -> solid
Freezing
solid -> liquid
melting
Liquid -> gas
evaporating
Solid -> Gas
Sublimation
What change are state changes?
Physical
Element
a substance that contains one type of atom
Compound
2 or more elements chemically bonded togetther
mixture
2 or more substances that are NOT chemically boded together
Purity
when somethign is pure , it is the only substance in it. a pure substance has the same composition everywhere
insoluble
wont dissolve in water
solute
thing being dissolved
solvent
the liquid that is doing the dissolving
solution
solvent and solute
what is chromatography for?
finding out which color compunds are in a mixture
what does it mean if a spot is higher up?
its a lighter compound
what is an easy indicator if and Rf value is wrong?
its more than 1
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What is Rf
distance moved by spot / distance moves by solvent
de- salination
producing pure water from sea water
why should the water from chemical analysis not be salty
it could precipitate, makes the water cloudy and cant read or could throw off results.
Pure
a susbtanc completely made of 1 compound or element
Why can u test if a substance is pure
Pure substances have specific sharp melting and boiling points due to all the atoms being the same, having the same prperties
How do you test for purity?
Compare the substances melting point to the expected value
What is simple distillation used for?
seperating a liquid out from a solution
Steps for simple distillation
- pour your sample of seawater into the flask
- set up apparatus, connect condenser to a cold tap using rubber tubing.
- gradually heat the distillation flask - the part of the solution with the slowest boilng point will evaporate (water)
- Eventually just the solute ( salt) will be left in the flask
Issues with simple distillation
- You can only use it to seperate things with very different boiling points
- Fractional distillation is to be used for substances with similar boilign points
Steps of Fractional distillation
- Put your mixture in a flask, attach a fractioning colum and condenser as shown
- Gradually heat the flask, different liquids will al have different boiling points - they will evaporate at different temperatures
- The liquid with the lowest boilign point ill evaporate first, when the temperature on the thermometer matches it boiling point, it will have reached the top of the colum
- ## Liquids with higher boiling points may also start to evaporate, but the colum is cooler at you go up so they will condense and run down the tube
what is filtration used for?
to seperate an insoluble solid from a liquid
How does filtration work?
Put some filter paper into a funnel and pour the mixture through, the solid will be caught in it and the liquid will filter through
What is crystallisation used for?
to seperate a soluble solid from a solution
How does crystallisation work?
Pour the solution into an evaportating dish and gently heat the solution, some of the water will get evaporated and the solution will become more concentrated.
once most of the water has evaporated or crystals start to form, remove the dish from the heat and leave the solution to cool. then filter it
What is chromatography used for?
to seperate a mixture of soluble substances and identify them
What are the two phases of chromatography?
a mobile phase
a stationary phase
Mobile phase (chromatography)
where the molecules can move, this is always a liquid or a gas
Stationary phase (chromatography)
where the molecules cant move - this can be a solid or a really thick liquid
What happens in chromatography?
the components in the mixture seperate out as the mobile phase moves over the stationary phase - they all end up in different places
Why do the componets of a mixture spread in chromatography?
each of the chemicals in a mixture will spend different times dissolved int he mobile phase and stuck in the stationary phase
What is the mobile phase in paper chromatography?
a solvent ( water or ethanol )
What is the stationary phase in paper chromatography?
the filter paper
How do you do paper chromatography?
Draw a line - thats the baseline
Put a spot of the mixture on the baseline
put some of the solvent into the beaker and dip the paper into it ( but not the dot)
put a watch glass over the beaker to prevent the solvent evaporating
the solvent will start to move up the paper, when the compounds dissolve they will also start to move up the paper
remove the paper from the beaker once the solvent reaches the top
What should you use to draw a baseline in chromatography?
A pencil as pencil marks are insoluble
How is the amount of time the molecules spend in each phase of chromatography affected
- how soluble they are in the solvent
- how attracted they are to the stationary phase
Molecules with higher solubility will move further up the paper
What is the final product peice of paper called in chromatography?
Chromatogram
What do you do if you have colorless compounds in your mixture ( Chromatography )
Spray the chromatogram with a chemical called a locating agent
What is Rf (words)
the ratio between the distance travelled by the dissolved substance ( solute) and the distance traveleed by the solution
How do you mesure distance travelled by solute/solution in chromatography?
From the baseline to the centre of the dot
What would a control for chromatography look like?
Using a pure sample at the dot - called a Standard Reference Material
What should a pure subtance do in chromatography?
Move as one dot
What could you do to analyse mixtures?
Combine seperation techniques
What is an example of combining seperation tecnniques to analyse mixtures?
Simple distillation and chromatography to analyse ink
What is ink?
A mixture of dyes dissolved in a solvent
What does potable water mean?
Water that is fit to drink
What are the 3 sources of potable water in the UK?
1) Surface water
2) Ground water
3) Waster water
What is surface water?
water from lakes, rivers and reservoirs. In alot of England and Wales, these sources dry in summer months
What is ground water?
Water from aquifiers ( rocks that trap water underground ). In parts of south-east england, where surface water is very limited, as much as 70% of water is from aquifiers.
What is waste water?
From water thats been contaminated by a human process
e.g a by product of industrial work. Treating this water to make it potable is preferable than to dispose of the water, which can be polluting. How easy wate water is to treat depends on the contaminents in it.
Where is water purified?
Water treatment plants
Water treatment plants, how easy it is to purify water
This depends on the source, ground water is usually quite pure, but waste water and surface water needs alot of treatment.
1.
What are the 3 main processes of water plant purification?
Filtration
Sedimentation
Chlorination
Water plant filtration
Wire mesh screens out large twigs ect. then gravel and sand beds filter out other bits
Water plant sedimentation
Iron sulfate or aluminium sulfate is added to the water, which makes fine paritcles clump tgether and settle at the bottom, which is then taken out
Water plant chlorination
Chlorine gas is them bubbled through to kill harmfull bacteria and other microbes
Gaining potable water from sea water
im some very dry countries, sea water is distilled to male potable water
Distillation needs lots of energy , so its very expensive so is not used in the Uk very often
What kind of water should you use in chemical experements, why?
De-ionised water, as to not skew results
