2. States of Matter and Mixtures

Question 1

What are the three states of matter?

Answer 1

Solids, liquids, and gases

Question 2

Solid —> liquid

Answer 2

Melting

Question 3

Liquid —> solid

Answer 3

Freezing

Question 4

Liquid —> gas

Answer 4

Boiling / evaporating

Question 5

Gas —> liquid

Answer 5

Condensing

Question 6

Gas —> solid

Answer 6

Deposition

Question 7

Solid —> gas

Answer 7

Sublimation

Question 8

Characteristics of solids

Answer 8

• Particles very close together.
• Fixed shape and volume.
• Particles vibrate in a fixed position.
• Particles have less energy than liquids or gases.

Question 9

Characteristics of liquids

Answer 9

• Particles very close together.
• Fixed volume but can change shape and fill a container.
• Particles move and flow randomly past one another.
• Particles have less energy than gases but more than solids.

Question 10

Characteristics of gases

Answer 10

• Particles are far apart.
• Can change shape and volume to fill any container.
• Particles move randomly in all directions.
• Particles have more energy than solids and liquids.

Question 11

What does strong forces between particles mean?

Answer 11

• More energy is required to overcome these forces.
• High melting and boiling points.

Question 12

What does weak forces between particles mean?

Answer 12

• Less energy is required to overcome these forces.
• Low melting and boiling points.

Question 13

Define mixture

Answer 13

• Consists of two or more elements or compounds not chemically combined together.
• Can be separated.
• Chemical properties of each substance in the mixture are unchanged.

Question 14

What is a pure substance in chemistry?

Answer 14

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

Question 15

TRUE OR FALSE: Pure substances melt and boil at specific/exact temperatures, mixtures do not due to consisting of 2 or more elements or compounds.

Answer 15

True

Question 16

Explain simple distillation

Answer 16

Used to separate a pure liquid from a mixture of liquids with different boiling points. The liquid with lowest boiling point evaporates first. The vapour released passes through a condenser where is cools and condenses to form a pure liquid.

Question 17

Explain fractional distillation

Answer 17

• The​ ​many​ ​hydrocarbons​ ​in​ ​crude​ ​oil​ ​can​ ​be​ ​separated​ ​into​ ​fractions​ ​each of​ ​which​ ​contains​ ​molecules​ ​with​ ​a​ ​similar​ ​number​ ​of​ ​carbon​ ​atoms.
• The​ fractionating​ ​column​ ​works​ ​continuously,​ ​heated​ ​crude​ ​oil​ ​is​ ​piped​ ​in at​ ​the​ ​bottom.​ ​
• The vaporised​ ​oil​ ​rises​ ​up​ ​the​ column​ ​and​ ​the​ ​various fractions​ ​are​ ​constantly​ ​tapped​ ​off​ ​at​ ​the​ ​different​ ​levels​ ​where​ ​they condense.
• The​ ​fractions​ ​can​ ​be​ ​processed​ ​to​ ​produce​ ​fuels​ ​and​ ​feedstock​ ​for​ ​the petrochemical​ ​industry.

Question 18

Explain filtration

Answer 18

Separates mixtures of insoluble solids and liquids. Done by pouring the mixture through filter paper.
- The insoluble solid is trapped and left behind on the filter paper.
- The liquid runs through the filter paper and is collected below.

Question 19

Explain crystallisaton

Answer 19

Separates solutions into their constituent (different) parts: dissolved solids (solutes) and liquids (solvents).
- Heat the solution in an evaporating basin, e.g. with a Bunsen burner, so that the solvent evaporates.
- Eventually, crystals of the solute will form.
- We can collect the solvent by condensing it as it evaporates.

Question 20

Explain paper chromatography

Answer 20

Separates solutions with a number of different solutes (solids) in the solvent (liquid) - usually separating different coloured pigments (ink).
- Place a drop of the solution to be separated near the bottom of a piece of chromatography paper.
- Dip the very bottom of the paper into a suitable solvent.
- The solvent moves up the paper and carries the solutes in the solution with it.
- Different solutes move at different speeds, so they separate on the paper. The more soluble the substance is, the further up the paper it travels.

Question 21

What should pure substances show on a paper chromatogram?

Answer 21

Should only have one spot on the chromatogram.

Question 22

What should impure substances/mixtures show on a paper chromatogram?

Answer 22

Will show up with more than one spot on a chromatogram.

Question 23

How do you calculate Rf value in paper chromatography?

Answer 23

Distance moved by substance / distance moved by solvent

Question 24

Potable water

Answer 24

It is suitable for drinking so it must have:
- Low levels of microbes.
- Low levels of contaminating substances.
- It is not the same as pure water but is still safe.

Question 25

How can waste and ground water be made potable?

Answer 25

1) Sedimentation: large insoluble particles will sink to the bottom of the water.
2) Filtration: water is filtered through beds of sand which removes small insoluble particles.
3) Chlorination: chlorine gas is put through water to kill microbes.

Question 25

How can sea water be made potable by using distillation?

Answer 25

1) Filter the seawater.
2) Boil it.
3) Water vapour is cooled and condensed.

Question 26

Why does water need to be pure in analysis?

Answer 26

Because any dissolved salts could react with the substances you are analysing, leaving you with a false result.

Question 27

Mobile phase in chromatography

Answer 27

Liquid or gas

Question 28

Stationary phase in chromatography

Answer 28

Solid or viscous liquid

Question 29

TRUE OR FALSE: In chromatography, substances are picked up and carried by a mobile phase, which then moves through a stationary phase.

Answer 29

True