state of matter and mixtures Flashcards
states of matter, methods of purifying and separating substances
1
Q
describe the arrangement of particles in the solid state
A
- strong forces of attraction between partciles which hold them in fixed positions in a regular LATTICE ARRANGMENT
2
Q
describe the movement of particles in the solid state
A
- don’t move
- so all solids keep a definite shape and volume
- vibrate in fixed positions
-> the hotter the solid becomes the more they vibrate (so solids expand slightly when heated)
3
Q
describe the relative energy of particles in the solid state
A
- don’t have much energy
4
Q
describe the arrangement of particles in the liquid state
A
- do not keep a definite shape
- keep the same volume
5
Q
describe the movement of particles in the liquid state
A
- some forces of attraction
-> free to move past each other but do tend to stick together - constantly moving with random motion
-> hotter liquid gets the faster they move
-» so liquids expand slightly when heated
6
Q
describe the relative energy of particles in the liquid state
A
- more energy than in solid but less than in gas
7
Q
describe the arrangement of particles in the gas state
A
- don’t keep a definite shape or volume
- will fill any container
- when particles bounce of the walls of a container they exert a pressure on the walls
8
Q
describe the movement of particles in the gas state
A
- move constantly with a random motion
- hotter gas gets the faster they move
-> gases either expand when heated or their pressure increases - no forces of attraction between particles so are free to move
-> travel in straight lines and only interact when they collide
9
Q
describe the relative energy of particles in the gas state
A
- more energy than solid or liquid state
10
Q
- melting =
- freezing =
A
- melting = solid to liquid
- freezing = liquid to solid
11
Q
- evaporating =
- condensing =
A
- evaporating = liquid to gas
- condensing = gas to liquid
12
Q
subliming =
A
solid to gas
13
Q
explain the changes in arrangement, movement and energy of particles during the interconversions
A
- when a solid is heated its particles gain mroe energy
- particles vibrate more, this weakenes forces holding it together so it expands
- at certain temperature the particles have enough energy to break free from their positions
- liquid is heated and the particles gain even more energy
- this energy makes the particles move faster which weakens and breaks the bonds holding liquid together
- at a certain temperature the particles have enough energy to break their bonds
14
Q
what are the physical changes
A
- melting and freezing
- evaporating and condensing
- subliming
15
Q
what is a physical change contrasted with a chemical change
A
- physical change = states of matter changes, easy to undo
- chemical change = hard to reverse, bonds breaking in chemical reactions, atoms from substances you start off with are rearranged to form different substance (reactants to products)
16
Q
predict the physical state of a substance under specified conditions
A
- a solid is below the substances melting point
- a gas is above a substances boiling point
- a liquid is in between
ex - melting point is 8012 and boiling point is 1413 - so the substance is a solid below 801 and a gas above 1413 and a liquid in between, so if the substance is at 1000 degrees than is is a liquid as 1000 is in between a solid and a liquid
17
Q
explain the difference between the use of “pure” in chemistry compared with its everyday use
A
- in chemistry pure means a single element or compound
18
Q
explain the difference bwteen the a pure subastance and a mixture
A
- mixture = more than one compound present or different elements that aren’t all part of a single compound
19
Q
interpret melting point data to distinguish between pure substances which have a sharp melting point and mixtures which melt over a range of temperatures
A
- pure substances have a specific melting and boiling point
- ## mixture will melt gradually over a range of temperatures-> you can use this to test the purity of a substance by comparing the actual melting point of the sample with the expected value
20
Q
how to measure the melting point of a substance
A
- use a melting point apparatus
- this kit heats up a small sample of a solid very slowly
- so you can observe and record the exact temperatre tha tit melts at
- you can also use a water bath an a thermometer which is harder to control
21
Q
explain the types of mixtures that can be separated using simple distillation
A
- separating a liquid from a solution
22
Q
type of mixtures that can be separated with fractional distillation
A
- mixture of liquids
23
Q
type of mixture that can be separated by using filtration
A
- if the product is an insoluble solid to separate it out from the liquid reaction mixture
24
Q
types of mixture that can be separated by using crystallisation
A
- a soluble solid from a solution
25
types of mixture that can be separated using paper chromatography
- inks, dyes
26
steps of simple distillation
1. pour smple into distillation flask
2. set up apparatus
3. heat distillation flask
4. the lowest boiling point will evaporate
5. water vapour passes into condensor where it colls and condenses
6. then it flows back into the beaker and is collected
7. salt is left in flask
27
steps of fractional distillation
1. put mixture in flask
2. attach a fractionating colum and condenser above the flask
3. heat flask
-> different liquids have different boiling points so will evaporate at different temperatures
4. liquid with lowest boiling point evaporates first
5. when temperature on thermometer matches boiling point of this liquid it will reach the top of the column
6. liquids with higher boiling points might start to evaporate but the column is cooler towards the top so will only get part way up before condensing and running back down towards the flask
7. when first liquid has been collected, raise the temperature until the next one reaches the top
28
steps of filtration
1. filter paper in funnel
2. pour in mixture
3. liquid par runs through paper
4. leaving behind solid residue
29
steps of crystallisation
1. pour solution into evaporating dish and heat
2. some water will evaporate and the solution will get more concentrated
3. once some has evaporated or crystals form remove dish from heat and let it cool
4. salt should form crystals as it becomes insoluble in the cold, highly concentrated solution
5. filter crystals out of the solution
6. leave them in a warm place to dry
30
steps of paper chromatography
1. draw line near bottom of paper with pencil
2. put spot of mixture to be separated on the line
3. put solvent into beaker
4. dip bottom of paper but not the spot into the solvent
5. put watch glass on the top of the beaker to stop any solvent from evaporating away
6. the solvent will start to move up the paper
7. when chemicals in mixture dissolve in the solvent they will move up the paper too
8. will see different chemicals in the sample separate out forming spots at different places on the paper
9. remove the paper from the beaker before the solvent reaches the top
10. mark the distance the solvent has moved (solvent front) in pencil
31
how to choose the right purification method
- simple distillation is one liquid, fractional is multiple
32
describe paper chromatography
- separation of mixtures of soluble substances by running solvent (mobile phase)
- through the mixture on the paper (the paper contains the stationary phase)
- which causes the substances to move at different rates over the paper
33
interpret a paper chromatogram to distinguish between pure and impure substances
- a pure substance won't be separated by chromatography
- it'll move as one blob
- a mixture should give you multiple blobs
34
interpret a chromatogram to identify substances by comparison with known substances
- Two substances are likely to be the same if:
- they produce the same number of spots, and these match in colour.
- the spots travel the same distance up the paper (have the same Rf value)
35
interpret a paper chromatogram to run a pure sample of a substance that might be your mixture alongside a sample of the mixture itself
- to see if a certain substance is present in as mixture
- if the sample has the same Rf values as one of the spots they are likely to be the same
- chemists can run samples of pure substances called standard reference materials next to a mixture to check the identities of its components
36
interpret a paper chromatogram to identify substances by calculation and the use of Rf values
- an Rf value is the ratio between the distance travelled by the dissolved substance (solute) and the distance travelled by the solvent
- to find the distance travelled by the solute measure the base line to the centre of the spot
37
investigate the composition of inks using simple distillation and paper chromatography
1. ink is a mixture of different dyes dissolved in a solvent
2. simple distillation to get what solvent the ink contain so you can evaporate off the solvent and collect it (assuming solvent has the lowest boiling point of all the substances in the ink it will evaporate first)
3. the thermometer will read the boiling point of the solvent when it is evaporating (and so being collected)
4. you can use the boiling point of the solvent to try and determine what is is
5. could then carry out paper chromatography on a sample of the ink so it will separate out the different dyes in the ink so you can see how many there are
6. can compare the Rf values of the different spots with reference values (or run further chromatography experiments with the pure substances) to work out what dyes are in the ink
38
describe how waste and ground water can be made potable
1. filtration (wire mesh screens out large twigs and solid bits)
2. sedimentation ( iron sulfate or aluminium sulfate is added to water which makes fine particles clump together and settle at the bottom)
3. chlorination (chlorine gas is bubbles through to kill harmful bacteria and other microbes)
39
sea water can be made potable using
distillation
40
describe how water used in analysis must not contain any dissolved salts
- deionised water = has ions present in normal tap water removed
- we do this as it could give experiment a false result
- for experiments involving mixing and dissolving something in water
