C2.1: Purity And Separating Mixtures

Question 1

What is relative atomic mass?

Answer 1

Relative atomic mass tells us how heavy an atom is compared to 1/12th of a carbon-12 atom.

Question 2

What does a chemical formula show you?

Answer 2

How many of each element there are in a unit of a substance

Question 3

What is relative atomic number?

Answer 3

How many protons there are in an element

Question 4

What is the empirical formula?

Answer 4

The simplest whole-number ratio of the atoms of each element in a compound

Question 5

What is a pure substance?

Answer 5

A substance that consists of one element or compound. It is often difficult to get pure substances.

Question 6

What is an impure substance?

Answer 6

A substance that consists of more than one element

Question 7

How can we identify if a subtance is pure or impure?

Answer 7

Pure substances have a sharp melting point
Impure substances melt over a range of temperatures

Question 8

What is an example of a mixture?

Answer 8

An alloy which is a mixture of a metal with one or more other elements

Question 9

What is a melting point?

Answer 9

The temperatute at which a substance changes from the solid state to a liquid state

Question 10

What is filtration?

Answer 10

Separates an insoluble substance in the solid state from substances in the liquid state

Question 11

How do you determine the melting point?

Answer 11

By heating a substance:
Measure the temperature at which it melts

Question 12

When does a solution form?

Answer 12

When one substance dissolves in another

Question 13

What is a solute?

Answer 13

The substance that dissolves

Question 14

What is a solvent?

Answer 14

The substance the solute dissolves in

Question 15

What happens when something dissolves?

Answer 15

The solutes particles separate and become completely mixed with the particles of the solvent

Question 16

What does the term soluble mean?

Answer 16

When a substance can dissolve in a particular solvent

Question 17

What does the term insoluble mean?

Answer 17

When a substance cannot dissolve

Question 18

How does filtration work?

Answer 18

Separates an insoluble substance in the solid state from substances in the liquid state

Question 19

What is actually used in filtration to filter the solid from the liquid?

Answer 19

Filter paper

Question 20

What is crystallisation?

Answer 20

Used to produce solid crystals from a solution. When the solution is warmed, some of the solvent evaporates leaving crystals behind.

Question 21

What happens when you conduct crystallisation at too strong temperatures?

Answer 21

You will get a powder instead of crystals

Question 22

What is simple distillation?

Answer 22

Separates a solvent from a solution. It relies on the solvent having a lower boiling point than the solute

Question 23

What apparatus is required in simple distillation?

Answer 23

Bunsen burner
Round-bottom flask
Thermometer
Condenser
Test tube

Question 24

What is fractional distillation?

Answer 24

A type of distillation that separates two or more substances from a mixture in the liquid state. Both liquids must have a different boiling point and a special equipment called a fraction unit column.

Question 25

What is chromatography?

Answer 25

A process by which it can separate complex mixtures into their component parts

Question 26

What are the 2 different chemical phases in chromatography?

Answer 26

1) stationary phase - does not move 2) mobile phase - does move

Question 27

What is the stationary phase in paper chromatography?

Answer 27

The absorbent paper

Question 28

What is the mobile phase in paper chromatography?

Answer 28

The solvent in the liquid state - such as the water

Question 29

What is the stationary phase in thin-layer chromatography?

Answer 29

A thin layer of either: - alumina powder - silica Spread over a plate of glass or plastic

Question 30

What is the mobile phase in thin-layer chromatography?

Answer 30

Solvent in the liquid state

Question 31

Briefly explain the process of paper chromatography

Answer 31

Used to separate mixtures of dyes or inks. A drop of the mixture is placed on filter paper. The paper is dipped in a solvent, which moves up the paper. Different substances travel at different speeds, separating into distinct spots.

Question 32

What is the baseline in chromatography?

Answer 32

the starting point from which the movement of these components is measured

Question 33

What is the solvent front in chromatography?

Answer 33

The point that the solvent has reached as it moves up the paper

Question 34

Briefly explain the process of filtration

Answer 34

Separates an insoluble solid from a liquid. A mixture is poured through filter paper in a funnel. The solid stays on the paper (residue), while the liquid (filtrate) passes through.

Question 35

Briefly explain the process of distillation

Answer 35

Separates a liquid from a solution based on boiling points. The solution is heated until the liquid evaporates. The vapor is cooled in a condenser, turning it back into a liquid. The pure liquid is collected, leaving impurities behind.

Question 36

Briefly explain the process of Thin Layer Chromatography

Answer 36

Similar to paper chromatography but uses a thin layer of silica gel or alumina on a glass or plastic plate. The sample is spotted onto the plate, which is placed in a solvent. Different substances travel at different speeds, separating for identification.

Question 37

Briefly explain the process of fractional distillation

Answer 37

Separates two or more liquids with different boiling points. The mixture is heated, and the liquid with the lowest boiling point evaporates first. A fractionating column improves separation by allowing repeated condensation and evaporation. The vapors are cooled, condensed, and collected separately.

Question 38

How do you calculate the Rf value?

Answer 38

Distance travelled by the substance / distance travelled by the solvent

Question 39

What is the stationary phase in gas chromatography?

Answer 39

The stationary phase is silica or alumina powder packed into a metal column

Question 40

What is the mobile phase in gas chromatography?

Answer 40

The mobile phase is an unreactive gas (like nitrogen) which doesn’t react with solvent

Question 41

Briefly describe the process of gas chromatography

Answer 41

It helps separate and identify different gases or liquids that evaporate easily. The sample is turned into a gas and pushed through a long tube by a gas like helium. Inside the tube, different substances move at different speeds, so they separate. A detector at the end records when each substance comes out. The results show as peaks on a graph, helping scientists figure out what’s in the sample. Used for drug tests, crime investigations, and checking food or air quality.

Question 42

Advantages of thin layer chromatography

Answer 42

Quicker More sensitive so smaller sample can be used Larger range of stationary phases and solvents to choose from

Question 44

What is filtration used to separate?

Answer 44

An insoluble solid from a liquid

Question 45

What is crystallisation used to separate?

Answer 45

A soluble solid from a solution

Question 46

What is simple distillation used to separate?

Answer 46

A solvent from a solution

Question 47

What is fractional distillation used to separate?

Answer 47

One or more liquids from a mixture of liquids

Question 48

What is chromatography used to separate?

Answer 48

Coloured soluble substances