C2.1 - Purity And Separating Mixtures

Question 1

what is a pure material

Answer 1

a material that is composed of only one type of particle with distinct chemical properties

Question 2

what is a mixture

Answer 2

two or more pure substances in which each pure substance retains its individual chemical properties

Question 3

what is an alloy

Answer 3

a mixture of (at least) 2 elements, one of which is a metal

Question 4

what are some properties of an alloy

Answer 4

strong, malleable, corrosion resistant

Question 5

where are the atoms in an alloy

Answer 5

in an alloy, the atoms of the second element fit into the spaces between the metal atoms

Question 6

what molecules does pure water contain

Answer 6

pure water contains water molecules

Question 7

what atoms does pure gold contain

Answer 7

pure gold contains gold atoms

Question 8

where are the atoms in a normal metal

Answer 8

in a normal metal, the atoms are arranged, in a regular structure

Question 9

why are most alloys stronger than metals

Answer 9

because the layers in alloys cannot slide over each other easily (because of the arrangement of atoms in an alloy)

Question 10

how can you check the purity of a substance

Answer 10

by comapring the boiling point of the substance to the specific boling point at room temperature

Question 11

what causes the substnace to boil at a different temperature

Answer 11

any impurities cause the substance to boil at different temperature

Question 12

what is a solution

Answer 12

a solute dissolved in a solvent

Question 13

what is a solute

Answer 13

a substance that is dissolved in a solvent

Question 14

what is a solvent

Answer 14

a liquid in which chemical dissolve to make a solution (e.g. water, ethanol)

Question 15

what is an aqueous solution

Answer 15

a solution where the solvent is water

Question 16

what happens in filtration

Answer 16

a solid is separated from a liquid (e.g. copper oxide in copper sulfate solution)

Question 17

what happens in crystallisation

Answer 17

a solvent is evaporated off to leave behind) a solute in crystal form (e.g. salt in water

Question 18

what happens in distillation

Answer 18

two liquids with significantly different boiling points are separated i.e. when heated, the liquid with the lowest boiling point evaporates first and the vapour is condensed and collected

Question 19

what happens in fractional distillation

Answer 19

a mixture of liquids with different boiling points are separated (e.g. petrol from crude oil)

Question 20

what happens in chromatography

Answer 20

substances in a mixture are separated using a stationary phase and a mobile phase

Question 21

what is a stationary phase

Answer 21

a fixed absorbant material e.g. paper (used for simple paper chromatography), or gel on a solid plate (for thin layer chromatography)

Question 22

what is a mobile phase

Answer 22

the solvent which carries the soluble compounds of the mixture

Question 23

what is paper chromatography useful for

Answer 23

paper chromatography is useful for separating mixtures of dyes in solution (e.g. dyes in ink)

Question 24

is thin layer chromatography or paper chromatography more accurate

Answer 24

thin layer chromatography is more accurate

Question 25

what is used in thin layer chromatography

Answer 25

in thin layer chromatography a thin layer of an insert solid is used for the stationary phase

Question 26

what does gas chromatography separate

Answer 26

gas chromatography separates gas mixtures by passing them through a solid stationary phase

Question 27

what is the equation for Rf

Answer 27

Rf = didtance moved by the compound ÷ disstance moved by the solvent

Question 28

what are some examples of water soluble mixtures

Answer 28

inks, dyes/paints,, colouring agents

Question 29

what is the Rf value used to calculate

Answer 29

the Rf values are used to calculate substnaces separated by chromatography