States of Matter

Question 1

What is the arrangement and movement of particles in solids?

Answer 1

Tightly packed together in a regular arrangement and vibrate in fixed positions

Question 2

What is the arrangement and movement of particles in liquids?

Answer 2

Close together but able to move past each other and vibrate and move around each other

Question 3

What is the arrangement and movement of particles in gases?

Answer 3

Well separated with no regular arrangement and vibrate and move freely at high speeds

Question 4

Compare the relative energies of particles in solids, liquids and gases

Answer 4

Particles in a solid have the least amount of energy and particles in a gas have the most energy

Question 5

What does ‘interconversion of state’ mean?

Answer 5

When matter changes from one state to another die to changes in temperature or pressure

Question 6

What are the forces between particles in solids, liquid and gases?

Answer 6

Solids - strong forces of attraction between particles which keeps them in their fixed positions, liquids - weaker attractive forces than in solids and gases - weakest intermolecular forces so particles are in random movement

Question 7

How does a physical change differ from a chemical change?

Answer 7

A physical change involves changes in the forces between particles, the particles themselves remain the same and the chemical properties remain the same whereas a chemical change is different as it affects the chemical properties of the substance

Question 8

Why are physical changes relatively easy to reverse?

Answer 8

there is no new product is formed during the changes of state

Question 9

What happens when a solid is heated and melts into a liquid?

Answer 9

When heated the particles absorb thermal energy which is converted into KE, the particles in the solid vibrate more, this causes the solid to expand until the structure breaks and becomes a liquid

Question 10

What happens when a liquid is heat and evaporated into a gas?

Answer 10

When heated, the particles in a liquid expand and some particles on the surface gain sufficient energy to overcome the intermolecular forces and evaporate, the boiling point all of the liquid particles gain enough energy to evaporate

Question 11

What is a mixture?

Answer 11

Contains 2 or more elements or compounds that are not chemically combined together

Question 12

What is a pure substance?

Answer 12

A single element or compound, not mixed with any other substance

Question 13

How can you use melting point to distinguish between pure substance and mixtures?

Answer 13

Pure substance have a sharp exact melting point whereas mixtures melt over a range of temperatures since they consist of several elements/compounds

Question 14

When is simple distillation used?

Answer 14

Used to separate a pure liquid from a mixture of liquid, only works when the liquid have different boiling points

Question 15

How can ethanol be separated from water?

Answer 15

Distillation apparatus set up, mixture boiled, ethanol evaporates first and ethanol vapour cools in the condenser, condensing back to a liquid before being collected

Question 16

When is fractional distillation used to separate mixtures?

Answer 16

Fractional distillation is used to separate all the elements/compounds in a mixture, these chemicals must have different boiling points to be separated

Question 17

What is the difference between fractional and simple distillation?

Answer 17

Simple distillation is only able to separate the liquid with the lowest boiling point from the mixture whereas fractional distillation separates all the chemicals in a mixture, using their different boiling pointsn

Question 18

How does fractional distillation work?

Answer 18

Oil is heated until it evaporates into the fractionating column and vapours rise up the fractionating column and condense at the different fraction, depending on the relative boiling point of each substance

Question 19

What sort of mixture can filtration be used to separate?

Answer 19

Filtration is used to separate an insoluble substance from a solution

Question 20

How can you separate an insoluble substance from a solution?

Answer 20

Place filter paper in a funnel, pour the solution containing an insoluble substance through the funnel into a conical flask and the insoluble substance will collect on the filter paper and the solution will collect in the conical flask

Question 21

When is the process of crystallisation used to separate a mixture?

Answer 21

To separate a soluble solid from a solution if the solid decomposes when heated

Question 22

How could you separate a soluble solid from a solution, if the solid decomposes when heated?

Answer 22

Crystallisation, pour the solution into an evaporating dish and heat gently, when the crystals start to form, remove the dish from the heat and leave to cool, once cold, filter the crystals out of the solution and leave them in a warm place to dry

Question 23

What process can be used to identify substances in a mixture?

Answer 23

Chromatography

Question 24

How does paper chromatography work to separate a mixture?

Answer 24

The mobile phase moves through the stationary phase so anything dissolved in the mobile phase will move with up the paper and compounds interact differently with each phase so will move different distances through the stationary phase meaning they will be separated

Question 25

How can chromatography show the composition of a mixture?

Answer 25

Different coloured substances in the mixture will separate as they have different solubilities in the solvent and will travel at different rates

Question 26

Why should pencil be used to draw the line along the bottom of the chromatography paper?

Answer 26

It won’t affect the experiment as it’s insoluble in the solvent

Question 27

Why should the water in the beaker for paper chromatography be no deeper than 1cm deep?

Answer 27

If it’s deeper it will wash away the substance placed on the line on the chromatography paper

Question 28

Why should you use a lid when carrying out paper paper chromatography?

Answer 28

To prevent the solvent evaporation

Question 29

How many spots will a pure substance produce on a chromatogram? How would this be different for an impure substance?

Answer 29

Pure substance produce one spot and an impure substance contains more than one compound so will produce more spots

Question 30

What is an Rf value?

Answer 30

The Rf value is the ratio between the distance travelled by the dissolved substances and the distance travelled by the solvent

Question 31

How do you calculate Rf values?

Answer 31

Distance travelled by substance / distance travelled by solvent

Question 32

When measuring measuring the distance moved by a substance in the chromatography paper, where should you measure between?

Answer 32

Measure from the pencil baseline to the middle of the spot of the substance

Question 33

How can you use chromatography to see if a certain substance is present in a mixture?

Answer 33

Run a pure sample of this substance alongside the unknown mixture and if the Rf value of the pure substance matches the value of one of the spots from the mixture, it’s likely to be present

Question 34

How could you separate salt from a mixture of salt and salt?

Answer 34

Salt is soluble in water, sand isn’t, add water to the mixture, filter the solution to remove the insoluble sand and then evaporate the water to collect the salt crystals

Question 35

How can liquids be separated if they have different densities?

Answer 35

If liquids have different densities they will naturally separate unto two layers and to separate these layers, use a flask with a tap on the bottom and open the tap to collect the bottom liquid

Question 36

What does potable mean?

Answer 36

Safe to drink

Question 37

How can waste and groundwater be made potable?

Answer 37

Sedimentation: large insoluble particles sink to the bottom after the water is left still for a while, Filtration: removes small insoluble particles by passing the water through layers of sand and filters and Chlorination: kills bacteria and microorganisms which are too small to be removed by filtration

Question 38

How can seawater be made potable?

Answer 38

Distilled, filter to remove insoluble particles, biol and Coll and condense the water vapour

Question 39

What issues surrounded the process of making seawater potable?

Answer 39

Extremely expensive as it’s requires a lot of energy to boil large volumes of water, wastewater is toxic due to the high concentration of salt so must be disposed of carefully

Question 40

What is deionised water?

Answer 40

Water that had had metallic ions removed

Question 41

Why is deionised water used in experimental analysis?

Answer 41

Deionised water is used to prevent ions in the water interacting with the substances under analysis, if water wasn’t deionised, false positive results may be produced