C2.1 Purity and separating mixtures

Question 1

What does relative atomic mass mean?

Answer 1

The mean mass of an atom of an element compared o 1/12 of the mass of a carbon atom

Question 2

What does chemical formula tell you?

Answer 2

Tells you how many atoms of each element there are in a unit of a substance

Question 3

What is an empirical formula

Answer 3

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

Question 4

What is a pure substance

Answer 4

A pure element consists of only one element or compound

Question 5

What is an alloy?

Answer 5

A mixture of a metal with one or more other elements.

Question 6

What is the melting point of a substance?

Answer 6

The temperature at which it changes from the solid state to the liquid state

Question 7

How would you know if a substance is impure using melting points

Answer 7

the melting point is less than that of the pure substance

Often melts over a range of temperatures not just one temperature

Question 8

How does a solution form?

Answer 8

When one substance dissolves in another

Question 9

What is a solute and solvent?

Answer 9

The substance that dissolves and the solvent is the substance it dissolves

Question 10

What does it means when a substance is soluble?

Answer 10

when the substance can dissolve in a particular solvent.

Question 11

How does filtration work?

Answer 11

Filtration separates an insoluble substance in the solid state from substances in the liquid state.It works because the filter paper has tiny, microscopic holes.When you filter a mixture of sand and water, water molecules are small enough to pass through the filter paper, but the large grains of in soluble sand cannot.The sand stays behind in the filter paper as the residue while the water passes through as the filtrate.Particles of a dissolved solute are also small enough to pass through filter paper

Question 12

How does crystallisation work?

Answer 12

IF you heat a solution the solvent evaporates leaving the solute behind.If you heat the solution too strongly, you het a powder hut if uu allow the solvent to evaporate slowly you het regularly shaped crystals.

Crystillisation takes patience as you need to heat the solution gently until it becomes a saturated solution.Asolution is saturate when no more solute can be dissolved at that temperature Crystals start forming at this point. so you then let the solution cool slowly.As the solution cools, the solubility of the solute decreases so more crystals form

Question 13

What does simple distillation separate?

Answer 13

Separates a solvent from a solution.

Question 14

What does fractional distillation do

Answer 14

Separates two or more substances from a mixture in the liquid state

Question 15

What stages does chromatography rely on

Answer 15

A stationary phase that does not move

A mobile phase that does move

Question 16

What happens in paper chromatography

Answer 16

The stationer phase is absorbent paper

the mobile phase is a solvent in the liquid state such as water or propane

Question 17

What does gas chromatography do

Answer 17

Separates the components of a mixture and also measures their amounts

Question 18

What can you use to tell if a substance is pure

Answer 18

You can use paper chromatography or thin layer chromatography to tell if a substance is pure but thin layer chromatography has some advantages

it is quicker
It is more sensitive so a smaller sample can be used
there is a larger range of stationer phases and solvents to choose from

Question 19

What separation method would you use for insoluble and soluble substances?

Answer 19

dissolving followed by filtration

Question 20

What seperation method would you use for a solute dissolved in a solvent (a solution )?

Answer 20

Crystillisation to obtain the solute, simple distillation to obtain the solvent

Question 21

What seperation method would you use to separate two or more substances in the liquid state?

Answer 21

fractional distillation

Question 22

what seperation mixture would you use to separate coloured soluble substances

Answer 22

paper chromatography or thin layer of chromatography

Question 23

Label the parts of the filtration method

Answer 23

Funnel
Filter Paper
Residue
Filtrate

Question 24

What is an affinity?

Answer 24

natural attraction or force between things

Question 25

What is the mobile phase in chrometography?

Answer 25

A gas or liquid that carries the component

Question 26

What is stage 1 of chromatography?

Answer 26

A pencil line is drawn near the bottom of a piece of chromatography paper

Along this line evenly spaced crossess are drawn

Question 27

What is stage 2 of chromatography?

Answer 27

A sample of the unknown food colouring to be tested is plaved on the first cross.

Samples of known food dye are placed on the other crossess

Question 28

What is stage 3 of chromatography?

Answer 28

The bottom of the paper is placed in a solvent. Water and ethanol are often used as solvents.

Question 29

What s stage 3 of chromatography?

Answer 29

The bottom of the paper is placed in a solvent. Water and ethanol are often used as solvents

Question 30

What is stage 4 of chromatography?

Answer 30

The solvent travels up the paper and the dues travel with it.

The size of the molecules in each dye affects the distance travelled up the paper

Question 31

What is stage 5 of chromatography?

Answer 31

Food colouring often contains a mixture of dyes.

These separate during chromatography and can be compared to known substances

Question 32

What is the formula fo Retention Factor Values (RF)

Answer 32

Distance from the baseline to the solvent front