States Of Matter And Mixtures

Question 1

Describe the arrangement and movement of particles in solids

Answer 1

Tightly packed together in a regular arrangement

Vibrate in fixed positions

Question 2

Describe the arrangement and movement of particles in liquids

Answer 2

Close together but able to move pass each other

Vibrate and move around each other

Question 3

Describe the arrangement and movement of particles in gases

Answer 3

Well separated with no regular arrangement

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 soiled have the lease 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 due to changes in temperature or pressure

Question 6

What are the names for the state changes from solid to liquid and vice versa

Answer 6

Solid —> liquid : melting
Liquid —-> solid : freezing

Question 7

What are the names for the state changes from liquid to gas and vice versa

Answer 7

Liquid —> gas : evaporation
Gas —> liquid : condensation

Question 8

Describe the forces between particles in solids

Answer 8

Strong forces of attraction between particles which keeps them in their fixed positions

Question 9

Describe the forces between particles in liquids

Answer 9

Weaker attractive forces in solids

Question 10

Describe the forces between particles in gases

Answer 10

Weakest intermolecular forces so particles are in random movement

Question 11

How does a physical change differ from a chemical change

Answer 11

The physical change involves changes in the forces between particles, the particles themselves remain the same and the chemical properties remain the same.

A chemical change is different as it affects the chemical properties of the substance

Question 12

Are physical changes relatively easy to reverse

Answer 12

Yes. Relatively easy to reverse since no new product is formed during the changes of state

Question 13

What is the term describing when a solid changes straight into a gas

Answer 13

Sublimation

Question 14

Describe what happens, in terms of particles, when a solid is heated and melts into a liquid

Answer 14

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

Question 15

Describe what happens, in terms of particles, when a liquid is heated and evaporates into a gas

Answer 15

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

Question 16

What is a mixture

Answer 16

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

The chemical properties of each substance in the mixture are unchanged

Question 17

What is a pure substance

Answer 17

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

Question 18

How can you use melting point data to distinguish between pure substances and mixtures

Answer 18

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

Question 19

When is simple distillation used

Answer 19

Used to separate a pure liquid from a mixture of liquids. Only works when the liquids have different boiling points

Question 20

When is fractional distillation used to separate mixtures

Answer 20

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

Question 21

What is the difference between fractional and simple distillation

Answer 21

Simple is only able to separate the liquid with the lowest boiling point from the mixture

Fractional separates all the chemicals in a mixture, using their different boiling points

Question 22

How does fractional distillation work

Answer 22

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

Question 23

What sort of mixtures can filtration be used to separate

Answer 23

Filtration is used to separate an insoluble substance from a solution

Question 24

Describe how to spreads an insoluble substance from a solution

Answer 24

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

Question 25

When is the process of crystallisation used to separate a mixture

Answer 25

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

Question 26

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

Answer 26

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 27

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

Answer 27

Chromatography

Question 28

How does paper chromatography work to separate a mixture

Answer 28

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

Question 29

How can chromatography show the composition of a mixture

Answer 29

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

Question 30

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

Answer 30

It will not affect the experiment as it is insoluble in the solvent

Question 31

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

Answer 31

If it is deeper it will wash away the substances placed on the line on the chromatography paper

Question 32

Why should you use a lid when carrying out paper chromatography

Answer 32

To prevent the solvent evaporating

Question 33

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

Answer 33

Pure substances produce one spot An impure substance contains more than one compound so will produce more spots (one spot for each chemical)

Question 34

What is an Rf value

Answer 34

The Rf value is the ratio between the distance travelled by the dissolved substance (the solute) and the distance travelled by the solvent

Question 35

How do you calculate Rf values

Answer 35

Rf = distance travelled by substance / distance travelled by solvent

Question 36

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

Answer 36

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

Question 37

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

Answer 37

Run a pure sample of this substance alongside the unknown mixture If the Rf value of the pure substance matches the value of one of the spots from the mixture, it is likely to be present

Question 38

True or false Substances with higher solubility in the solvent will travel further up the chromatography paper

Answer 38

True (They will stay dissolved in the solvent (mobile phase) for longer)

Question 39

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

Answer 39

Salt is soluble in water, sand is not Add water to the mixture Filter the solution to remove insoluble sand Evaporate the water to collect salt crystals

Question 40

How can liquids be separated if they have different densities

Answer 40

Naturally separate into two layers To separate these layers, use a flask with a tap on the bottom. Open the tap to collect the bottom liquid (has highest density)

Question 41

What does potable mean

Answer 41

Safe to drink

Question 42

How can waste and ground water be made potable

Answer 42

1. Sedimentation - large insoluble particles sink to the bottom after the water is left still 2. Filtration - removes small insoluble particles 3. Chlorination - kills bacteria and microorganisms that are too small to be removed by filtration

Question 43

How can sea water be made potable

Answer 43

Distillation 1. Filter to remove insoluble 2. Boil 3. Cool and condense the water vapour

Question 44

What issues surround the process of making sea water potable

Answer 44

Extremely expense, as requires lots of energy to boil large volumes of water Wastewater is toxic due to high concentration of salt so must be disposed of carefully

Question 45

What is deionised water

Answer 45

Water that has had metallic ions removed