Mixtures and separations

Question 1

what is a pure substance

Answer 1

a pure substance is composed of a singe tpye of material only

Question 2

what is an element

Answer 2

a pure sub

Question 3

what is a compound

Answer 3

a pure substance that if fromed from two or more different types of elements which are chemically bonded together in fixed proportions in a way that there properites have changed

Question 4

give an example of a compound

Answer 4

sodium + chloride = sodium chloride

Question 5

what is a mixture

Answer 5

consists if two or more elements and/or compounds which are physically combined together in variable proportions. Each compnent retains its own individual properties and is not chemically bonded to any other compnet in the mixture

Question 6

what is a homogenous mixture

Answer 6

a uniform mixture; has the same composition and properties throughout the mixture. it is not possible to distingush the component parts from each other. all solutions are homogeneus mixtures

Question 7

what is a heterogenous mixture

Answer 7

a non unifrom mixture; possbile to distinguish the components parts from each other

Question 8

what is a solution

Answer 8

a homogeneous mixture of two or more substances; one substance is usually aa liquid

Question 9

what is a solvent and solute and their role in a solution

Answer 9

solvent does the dissolving and is in higher conc
solute is being dissolved and is in lower conc

Question 10

what is a saturated solution

Answer 10

a solution where the solvent cannot dissovle any more solute at a particular temperature in the presence of undissovled solute

Question 11

a solution where the solvent is water is called what?

Answer 11

aqueos solution

Question 12

what is a suspension and name 3 e.g

Answer 12

a hetero genous mixture where visible particles are dispersed in another substance e.g. mud in water, oil shaken in water, dust in air

Question 13

what is a colloid and name 3 e.g.

Answer 13

a heterogeneous mixture in which minure visible particles of one substance are dispersed in another substance, usually a liquid e.g. foam, emulsion, gel

Question 14

name the state of solute and solvent in sea water

Answer 14

Sodium Chloride(solute) dissovled in water(solvent)

Question 15

name the state of solute and solvent in White vinegar

Answer 15

ethonic acid dissovled in acid

Question 16

name the state of solute and solvent in soda water

Answer 16

carbon dissolved in water

Question 17

size of particles dispersed in solution?

Answer 17

extremely small

Question 18

size of particles dispersed in colloid

Answer 18

larger than those in a solution but smaller than those in a suspension

Question 19

size of particles dispersed in suspension

Answer 19

larger than thosee in a colloid

Question 20

Sedimentation in solution

Answer 20

components do not separate if left undisturbed

Question 21

Sedimentation in colloid

Answer 21

dispersed particles do not settle if left undisturbed

Question 22

Sedimentation in suspension

Answer 22

dispersed particles settle if left undisturbed

Question 23

Passage of light in solution

Answer 23

light usually passes through

Question 24

Passage of light in colloid

Answer 24

will scatter light

Question 25

Passage of light in suspension

Answer 25

light does not pass through

Question 26

what is solubility

Answer 26

the mass of solute that will saturate 100g of solvent at a specific temperature

Question 27

how is a seperating funnel used

Answer 27

used to separate two or more immicible liquids, e,g. oil and water, immicible liquids do not mix and are separated due to different densities

Question 28

what is simple filtration

Answer 28

used to separate a suspended or settled soliod and a liquid when the solid does not dissovle in the liquid, e,g soil and water. components are separated due to their different particles size

Question 29

what is fractional distillation

Answer 29

used to separate two or more misciblee liquids , separated due to their different boiling points

Question 30

what is simple distillation

Answer 30

used to seperate and retain the liquid solvent from the solid solute in a solution e.g. to obtain disttiled water from tap water or sea water, the components are seperated due to different boiling points

Question 31

describe the extraction of surcrose from sugar cane

Answer 31

1. cane is crushed and water is sprayed on to dissovle surcrose from cells 2. lime is added to **precipate** impurities and to neutralise the acidic juice to prevent sucrose breaking down 3.impurites are **filtered** 4. juice is concentrated by heating in a series of boilers at successivly reduced pressure this process is known as **vacuum distillation** 5.concentrated juice (syrup) is **crystillized** at low pressure to prevent caramelisation 6. sugar crystals is **centrifuged** to separate sugar crysstals and molassess

Question 32

show 3 differences between a mixture and pure substance

Question 33

explain how you would obtain pure water from tap water

Answer 33

fractional distillation