Topic 2- states of matter and mixtures (with spec) paper 1

Question 1

What is the arrangement, movement and relative energy of solid particles?

Answer 1

Arrangement: in fixed positions in a regular lattice arrangement, they hold a definite shape and volume

Movement: strong forces of attraction meaning they are in fixed positions, they can only vibrate about their fixed positions

Energy: don’t have much energy, the hotter the solid the more they vibrate so more energy

Question 2

What is the arrangement, movement and relative energy of liquid particles?

Answer 2

Arrangement: some forces of attraction, they’re free to move around each other but they tend to stick together, don’t keep a definite shape

Movement: the particles are constantly moving in a random motion, the hotter the liquid, the faster it moves

Energy: more energy than in solid state but less energy in gas state

Question 3

What is the arrangement, movement and relative energy of gas particles?

Answer 3

Arrangement: no force of attraction so they’re free to move, move constantly with random motion

Movement: they travel in straight lines and only interact when they collide, the hotter the gas the faster they move, when particles bounce off the walls they exert a pressure on the walls

Energy: the most energy in the three states

Question 4

What is the change when a substance changes from one state of matter to another?

Answer 4

Physical change

Question 5

What is the process from solid to liquid called?

Answer 5

melting

Question 6

What is the process from liquid to gas called?

Answer 6

evaporating

Question 7

What is the process from gas to liquid called?

Answer 7

condensing

Question 8

What is the process from liquid to solid called?

Answer 8

freezing

Question 9

What is the process from solid to gas called?

Answer 9

subliming

Question 10

What are chemical changes?

Answer 10

they happen during chemical reactions when bonds between atoms break and the atoms change places. compared to physical changes, chemical changes are often hard to reverse

Question 11

explain the changes in arrangement, movement and energy during the inter-conventions of state

Answer 11

when heated they gain more energy leading to an increase of vibrations and weakens the force that hold the solid together, making them expand. this will eventually cause for bonds to break

Question 12

What are pure substances?

Answer 12

a substance made up of a single element or compound. chemists sometimes need to be obtain s pure sample of a substance from a mixture.

Question 13

what is a mixture?

Answer 13

when a substance contains more than one compound or different elements which aren’t chemically joined, eg. air as it contains a mixture of nitrogen, oxygen and various other gases

Question 14

How can you test for purity?

Answer 14

By using melting points

Question 15

What is the bp and mp like in pure substances?

Answer 15

they have a specific, sharp mp and bp

Question 16

What is the bp and mp like in mixtures?

Answer 16

it will melt gradually over a range of temperatures rather than a sharp mp in pure substances

Question 17

Explain the separating experiment of simple distillation

Answer 17

1) put seawater into a distillation and attach a thermometer, condenser and place a beaker a the end of the condenser
2) connect the bottom end of the condenser to a a cold tap using rubber tubing and run cold water through the condenser to keep it cold
3) gradually heat the distillation flask so the part with the lower bp will evaporate, in this case the water
4) the water vapour will cool and condense in the condenser and then flows into the beaker where it is collected
5) eventually you’ll end up with just the salt left in the flask

Question 18

Explain the separating experiment of fractional distillation

Answer 18

an example of this is the separation of crude oil

1) put your mixture in a flask and attach the fractionating column and condenser above the flask
2) gradually heat the flask and you will see the liquid with the lowest bp evaporate first and then gradually rise the temperature until the next one reaches the top

Question 19

Explain the separating experiment of filtration

Answer 19

put some filter paper in a funnel and pour your mixture into it. the liquid part of the mixture will run through the paper, leaving the solid residue

Question 20

Explain the separating experiment of crystallisation

Answer 20

1) pour the solution into an evaporating dish and gently heated the solution
2) once some of the water has evaporated or when you see crystals forming turn off the heat and le the solution to cool
3) the salts should start to form crystals as it becomes insoluble in the cold
4) filter the crystals out of the solution and leave them to dry

Question 21

what is a solution?

Answer 21

particles dissolved into water

Question 22

what is a compound?

Answer 22

two different atoms which are joined together chemically

Question 23

what is a element?

Answer 23

substance that one has one type of atom

Question 24

what does homogenous mean?

Answer 24

all of the particles are the same throughout (pure)

Question 25

what does heterogenous mean?

Answer 25

all of the particles are different throughout (mixture)

Question 26

what does potable mean?

Answer 26

drinkable

Question 27

what is paper chromatography?

Answer 27

the separation of pictures of soluble substances by running a solvent through the mixture on the paper, which causes the substances to move at different rates over the paper

Question 28

what is the mobile phase in paper chromatography?

Answer 28

where the molecules can move, this is always a liquid or gas (water)

Question 29

what is the stationery phase in paper chromatography?

Answer 29

where the molecules can’t move. this can be a solid (the filter paper)

Question 30

Explain the separating experiment of paper chromatography

Answer 30

1) draw a line near the bottom of the paper which is the baseline with a pencil. put a spot of the mixture on the line
2) put some of the solvent (water) into a beaker and dip the bottom of the paper (but not the spot) into the solvent
3) the solvent will start to move up the paper and when the chemicals in the mixture dissolve into the solvent they will move up the paper too
4) you will see the different chemicals spreading out on the paper and forming different spots at different places on the paper
5) remove the paper from the beaker before the solvent reaches the top and mark the distance the solvent has moved (the solvent front)

Question 31

what does the amount of time the molecules spend in each phase depend on?

Answer 31

• how soluble they are in the solvent

- how attracted they are to the stationery phase

Question 32

what do molecules with a higher solubility in the solvent do?

Answer 32

they spend more time in the mobile phase than in the stationery phase so they’ll be carried further up the paper

Question 33

how can you do paper chromatography with substances that are colourless?

Answer 33

spray the chromatogram with a locating agent

Question 34

how do you calculate the Rf value for each chemical?

Answer 34

distance travelled by solute / distance travelled by solvent

Question 35

what is the solute in paper chromatography?

Answer 35

the ink

Question 36

what is the solvent in paper chromatography?

Answer 36

the water

Question 37

how do you find the distance travelled by solute?

Answer 37

measure from the baseline to the centre of the spot

Question 38

how do you use paper chromatography to distinguish pure and impure substances?

Answer 38

a pure substance won’t be separated by chromatography- it’ll move as one blob but with a mixture it should give you multiple blobs

Question 39

how can you use simple distillation and paper chromatography to investigate the composition of inks?

Answer 39

1) evaporate the solvent from the ink using simple distillation to collect it- assuming that the solvent has the lowest boiling point
2) the thermometer will read the temperature when it is evaporating to help you predict what the solvent is, eg. if it evaporated at 100ºC it is likely to be water
3) then carry out paper chromatography on a sample of the ink so it will separate the different dyes in the ink so you can see how many there are
4) you can compare the Rf values of the different spots to work out what dyes are in the ink

Question 40

how can water be made potable?

Answer 40

using filtration (a wire mesh screens out large twigs and gravel) then sedimentation (makes fine particles clump together and settle at the bottom) and then chlorination (chlorine gas is bubbled through to kill bacteria)

Question 41

how can seawater be made potable?

Answer 41

distillation

Question 42

what does water used in chemical analysis also be?

Answer 42

it must not contain any dissolved salts and must be pure