Topic 2: States of Matter and Mixtures

Question 1

Physical Change Defenition

Answer 1

A change in the form or appearance of matter, but its chemical composition stays the same. E.g. melting, freezing, boiling

Question 2

Chemical Change Defenition

Answer 2

A change in which atoms rearrange themselves to form new substances with different properties. E.g. burning, rusting

Question 3

Physical Change Characteristics

Answer 3

No new substance formed

Usually easily reversible

Usually no significant energy change

Usually no colour change

Question 4

Chemical Change Characteristsics

Answer 4

Reactants react to form products

Usually irreversible

Either exothermic or endothermic

Can result in colour change

Question 5

Properties of Solids

Answer 5

Strong intermolecular forces of attraction, regular lattice arrangement

Particles vibrate around a fixed position

Particles have low energy

Definite shape and volume
High density

Question 6

Properties of Liquids

Answer 6

Some forces of intermolecular attraction

Particles move around each other

Particles have more energy than solids

Definite volume, no definite shape

Medium density

Question 7

Properties of Gases

Answer 7

Minimal intermolecular forces of attraction

Particles move quickly in all directions

Particles have high energy

No definite shape or volume, always fills container (exerts pressure)

Low density

Question 8

Solid to Liquid

Answer 8

Melting

Question 9

Liquid to Gas

Answer 9

Evaporation

Question 10

Liquid to Solid

Answer 10

Freezing

Question 11

Gas to Liquid

Answer 11

Condensation

Question 12

Solid to Gas

Answer 12

Sublimation

Question 13

Gas to Solid

Answer 13

Deposition

Question 14

Evaporation vs Boiling

Answer 14

Evaporation: occurs at the surface of the liquid, below the boiling point, and is slower

Boiling: liquid turns into gas throughout the entire liquid, at the boiling point, and happens rapidly, producing bubbles.

Question 15

Pure Substance Defenition

Answer 15

Made of only one type of element or compound

Fixed composition

Distinct properties

Question 16

Mixture Defenition

Answer 16

Combination of two or more substances not chemically bonded

Can be separated by physical methods

Question 17

How can the purity of a substance be distinguished?

Answer 17

Pure substances have specific, sharp melting and boiling points

Mixtures have a range of melting and boiling points

Question 18

Cooling Curve Defenition

Answer 18

A graph which shows how a substance changes from a gas to a liquid to a solid as temperature decreases

Question 19

Separation techniques

Answer 19

Simple distillation

Fractional distillation

Crystallisation

Filtration

Chromatography

Question 20

What does simple distillation separate?

Answer 20

Separates a liquid from a soluble solid, or a pure liquid from a mixture of liquids

Question 21

How is simple distillation carried out?

Answer 21

Solution is heated, liquid evaporates and rises. It passes through the condenser, and cools turning into a liquid

Question 22

What does fractional distillation separate?

Answer 22

Separates a mixture of liquids, or 2 or more liquids that are miscible (liquid dissolves completely in another liquid)

Question 23

How is fractional distillation carried out?

Answer 23

Solution heated to temperature of substance with the lowest boiling point. Substance evaporates and rises. It passes through the condenser, and cools turning into a liquid

Question 24

When is simple/fractional distillation used?

Answer 24

Simple distillation: liquid from dissolved solid, or two liquids with very different boiling points

Fractional distillation: two or more liquids with closer boiling points

Question 25

What does filtration separate?

Answer 25

Separates an insoluble solid from a solution

Question 26

How is filtration carried out?

Answer 26

Filter paper is placed in a filter funnel above a beaker. Mixture is poured through. Only small liquid particles pass (filtrate). Solid stays as residue.

Question 27

What does crystallisation separate?

Answer 27

Separates a soluble solid from a solution

Question 28

How is crystallisation carried out?

Answer 28

Solution is heated, allowing solvent to evaporate leaving a saturated solution. The saturated solution cools slowly, and crystals form as lids come out of solution (due to decreasing solubility)

Question 29

What does paper chromatography separate?

Answer 29

Separates substances of different solubilities in a solvent (e.g. pigments)

Question 30

How is paper chromatography carried out?

Answer 30

Spots of sample are placed on pencil line (drawn on chromatograph paper). Paper is lowered into a spent container. Solvent travels up. Different substances have different solubilities so rise at different rates.

Question 31

Mobile phase

Answer 31

Where molecules can move: the liquid or gas

Question 32

Stationary phase

Answer 32

Where molecules can’t move: solid or thick liquid

Question 33

What determines how molecules move in paper chromatography?

Answer 33

How soluble they are in the solvent How attracted they are to the stationary phase

Question 34

How are mixtures represented on chromatograms?

Answer 34

Produce multiple separate spots

Question 35

How are pure substances represented on chromatograms?

Answer 35

Produce only one spot

Question 36

How are Rf values calculated?

Answer 36

Distance travelled by substance ÷ distance travelled by solvent Between 0 and 1

Question 37

Potable water defenition

Answer 37

Water that is safe to drink

Question 38

How is water purified?

Answer 38

Filtration: removes large insoluble particles, through sand/gravel filters Sedimentation: allows large insoluble particles to sink to the bottom Chlorination: kills bacteria and other microorganisms

Question 39

How is sea water made potable?

Answer 39

Sea water is distilled to separate salt Very expensive: requires lots of energy

Question 40

Water in chemical analysis

Answer 40

Deionised water should be used (ions removed) Ions in tap water could produce false results