SC1, SC2: States of Matter, Methods of Separating and Purifying Substances

Question 1

What are the three states of matter?

Answer 1

solids, liquids and gas

Question 2

What is the arrangement of particles in gas?

Answer 2

• random
• apart

Question 3

What is the arrangement of particles in liquids?

Answer 3

• random
• close together

Question 4

What is the arrangement of particles in solids?

Answer 4

• regular
• close together

Question 5

What is the movement of particles in gas?

Answer 5

• fast
• in all directions

Question 6

What is the movement of particles in liquids?

Answer 6

• move around each other

Question 7

What is the movement of particles in solids?

Answer 7

• vibrate
• fixed positions

Question 8

What are physical changes?

Answer 8

Changes that can be reversed and don’t alter the chemical properties of the substance and can be reversed. Only their movement, arrangement, and amount of stored energy is affected

Question 9

What type of change is a change in state?

Answer 9

Physical

Question 10

What are attractive forces?

Answer 10

Forces in which one object attracts the other

Question 11

In which state do particles have the most energy (at the same temperature)?

Answer 11

Gas

Question 12

Describe the properties of a solid

Answer 12

• fixed volume
• fixed shape
• cannot flow, because particles can’t move
• can’t be compressed because particles are close together and have no space to move into

Question 13

Describe the properties of a liquid

Answer 13

• fixed volume
• no fixed shape
• can flow and take the shape of the container because their particles can move around each other
• cannot be compressed easily because particles are close together and barely any space to move into

Question 14

Describe the properties of a gas

Answer 14

• no fixed shape or volume
• can flow and completely fill their container because their particles can move quickly in all directions
• can be compressed because particles are far apart and have space to move into

Question 15

What is sublimination?

Answer 15

When a solid turns straight into a gas on heating without becoming a liquid first, or vice versa

Question 16

What is a pure substance?

Answer 16

Has the same fixed composition in all its parts so we can’t separate it into other substances using physical methods

Question 17

What must we do to a substance to witness a change in state?

Answer 17

Heat it or cool it down

Question 18

What is the energy gained during a change of state used to do?

Answer 18

• break or overcome some bonds between particles during melting
• break or overcome all remaining bonds during evaporation

Question 19

During condensation and freezing, do particles gain or lose energy?

Answer 19

Particles lose energy as bonds form between them

Question 20

What is a mixture?

Answer 20

Contains elements and/ or compounds that are not chemically joined together

Question 21

Why is the melting point of a mixture different to that of a pure substance?

Answer 21

• a pure substance has fixed boiling and melting points because it has the same composition everywhere, therefore the physical properties are consistent throughout the substance
• a mixture has a range of melting and boiling points because they have a different composition everywhere

Question 22

What are filters used for?

Answer 22

To separate an insoluble solid from a liquid. It lets smaller pieces or liquids through but traps larger/ insoluble substances

Question 23

Define insoluble

Answer 23

Unable to dissolve in a certain solvent

Question 24

What is crystallisation used for?

Answer 24

To produce solid crystals from a solution. Used to separate the solvent from its solutes

Question 25

Define solutes

Answer 25

The substance that dissolves in a liquid to create a solution

Question 26

What is the effect of a slow formation of crystals?

Answer 26

Gives particles more time to form an ordered pattern, resulting in larger crystals

Question 27

What is simple distillation used for?

Answer 27

To separate a solvent from a solution

Question 28

What is distillation?

Answer 28

The action of purifying a liquid through a process of heating and cooling

Question 29

Why does distillation work?

Answer 29

The dissolved solute has a much higher boiling point than the solvent, causing the solvent to evaporate when the solution is heated to its boiling point, leaving behind the solute

Question 30

What is paper chromotography?

Answer 30

A technique used to separate the different components of a mixture

Question 31

Why does paper chromatography work?

Answer 31

Some compounds dissolve better in a solvent than others

Question 32

What are the two phases paper chromatography relies on?

Answer 32

• the stationary phase
• the mobile phase

Question 33

Describe what happens during the stationary phase

Answer 33

When the paper chromatography is an absorbent, uniform paper

Question 34

Describe the mobile phase

Answer 34

When the solvent moves through the paper, carrying the other substances in it

Question 35

What does separation by chromatography produce?

Answer 35

Chromatogram

Question 36

What is paper chromatography used to distinguish between?

Answer 36

pure and impure substances
—> Pure substances produce one spot on the chromatogram
—> Impure substances produce two or more spots

Question 37

What is the Rf value?

Answer 37

The distance the compound has risen divided by the distance the solvent has risen

Question 38

How do we calculate the Rf value?

Answer 38

distance moved by the spot/ distance moved by the solvent

Question 39

Describe a few methods used to treat water to make it potable

Answer 39

• Sedimentation: small particles allowed to clear out
• Filtration tank: water passed through sand and gravel to get rid of any more insoluble substances
• Chlorine gas is added to kill harmful microorganisms
• Drinking water tower tests the water to check if it is purified and scans for remaining harmful substances

Question 40

How can pure water be produced from seawater?

Answer 40

Simple distillation

Question 41

What is deposition?

Answer 41

When a gas turns directly into a solid without becoming a liquid first

Question 42

Define melting point

Answer 42

The temperature at which a solid becomes a liquid

Question 43

Define boiling point

Answer 43

The temperature at which a liquid becomes a gas

Question 44

What is the particle theory?

Answer 44

Matter is made up of tiny particles which are represented as small, solid spheres which are constantly moving

Question 45

Describe how sea water can be made potable by using distillation.

Answer 45

• Filtered sea water is boiled.
• The water vapour is cooled and condensed to from distilled water.

Question 46

Describe how waste and ground water can be made potable.

Answer 46

Step 1: Sedimentation - Large insoluble particles sink to the bottom of the tank.
Step 2: Filteration - small insoluble particles are removed by filtering through beds of sand.
Step 3: chlorination - chlorine gas is bubbled from the water to kill microbes.

Question 47

Explain how fractional distillation works.

Answer 47

When the mixture is heated:

• the mixture boils and vapour rises up.
• vapour condenses depending on its boiling point.

Question 48

Explain how Simple Distillation works.

Answer 48

When the solution is heated:

• the solvent boils.
• solvent gas passes into condenser.
• Vapour is cooled and condensed back to liquid state.

Question 49

Explain why water used for chemical analysis must not contain any salts.

Answer 49

Dissolved salts could react with the substances in the analysis, therefore intervening with the analysis.

Question 50

What is fractional distillation used for?

Answer 50

To separate liquids from a mixture of miscible liquids.

Question 51

What is simple distillation used for?

Answer 51

To separate a solvent from a solution