Topic 2

Question 1

Define independent variable and where it situated on a graph (2)

Answer 1

What is changed

always x axis on a graph

Question 2

Define dependent variable and where it situated on a graph (2)

Answer 2

what is measured

always y axis on a graph

Question 3

Define control variable

Answer 3

factor(s) which are controlled during the investigation

Question 4

which apparatus is used to measure time

Answer 4

stopwatch

Question 5

Which apparatus is used to measure temperature

Answer 5

thermometer

Question 6

Which apparatus is used to measure mass

Answer 6

mass balance

Question 7

Define SI units

Answer 7

standardised units for measuring

Question 8

Name the unit and symbol for electric current (2)

Answer 8

Unit: ampere

symbol: A

Question 9

1L is also equal to? (2)

Answer 9

1dm^3

1000cm^3

Question 10

Purpose of measuring cylinder

Answer 10

used to measure out a volume of liquid to be used in a reaction

Question 11

Purpose of pipette

Answer 11

used to transfer a volume of liquid from one vessel to another

Question 12

Purpose of burette (3)

Answer 12

used during titration reactions

Allows volume of liquid to be added to another and the addition of the liquid is controlled by a tap

scientist is then able to measure how much liquid was needed in the reaction

Question 13

Define precise results

Answer 13

a set of results, measurements or values that are close to each other

Question 14

Define accurate results

Answer 14

results, measurements or values that are close to the atual value

Question 15

name the different measurement techniques used to seperate mixtures (5)

Answer 15

filtration

fractional distillation

crystallisation

Distillation

Paper chromatography

Question 16

Explain filtration (4)

Answer 16

used to seperate insoluble solid from a liquid

solid gets stuck in the filter paper while the liquid is able to pass through

solid is known as residue

liquid is known as filtrate

Question 17

Explain evaporation (2)

Answer 17

used to seperate soluble solid from a liquid

liquid is evaporated off to leave behind the soluble solid

Question 18

Define pure substance

Answer 18

having only one type of particle

Question 19

Define impure substance

Answer 19

has more than one type of particle

Question 20

Relationship between melting/boiling point and purity (2)

Answer 20

pure substance has sharp melting and boiling point

pure substance has a set melting point and boiling point at which the intermolecular forces of attraction breaks

Question 21

Relationship between melting/boiling point and impurity (2)

Answer 21

graph for melting and boiling point of an impure sustance would show a slope with a gradient between the state changes (seperate componenets melt at different temperature so it cannot be a horzontal line)

impure substances melt over a range of tmperatuers

Question 22

Impure solids have a lower melting point than the pure solid

True or False

Answer 22

true

Question 23

A liquid with a solute will have a higher boiling
point than the pure solvent.

True or False

Answer 23

true

Question 24

where and Why is purity important? (2)

Answer 24

important in food and pharmaceutical industries

any impurities could have potential lethal side effects

Question 25

Explain crystallisation (3)

Answer 25

allows pure crystals of a solid to be obtained from a solution as it cools slower the cooling, the larger the growth of crystals crystals form when the temperature of the solution decreases meaning the solid particles have less space within the liquid. The solid particles are pushed out of the solution and grows as crystals.

Question 26

What is distillation used to seperate

Answer 26

used to seperate a liquid with a soluble solid

Question 27

When is distillation used over evaporation

Answer 27

used over evaporation when you want to obtain the liquid vs in evaporation when you want to obtain the solid

Question 28

Can liquids be used to seperate a mixture of liquids with different boiling points in distillation? EXPLAIN.

Answer 28

can be used to seperate a mixture of liquids with different boiling points. However, liquids must have boiling points that have a significant different in temperature

Question 29

Explain the process of distillation (5)

Answer 29

original source is heated within the round bottomed flask The liquid with the lower boiling point boils and changes state to gas the vapour passes along the condensor, where cold water runs through, acting as a heat exchanger and absorbing the heat from the gas until it turns back into a liquid liquid is collected in the beaker The other liquid (which has a higher b.p) is left behind in the rounded flask

Question 30

When is fractional distillation used (2)

Answer 30

used to seperate more complex liquid mixtures used when the different in boiling points of the seperate components is rougly 25degrees

Question 31

Explain process of fractional distillation (5)

Answer 31

mixture of liquids in the rounded bottomed flask is heated both substances start to vapourise because of their similar b.p vapour travels past the glass beads which have a cool surface area Vapour from the liquid with the higher b.p condenses and drops back into the flask the vapour from the other liquid mvoes through the top of the column and then into the condensor

Question 32

Use of fractional distillation in industry

Answer 32

used in the oil industry to seperate out crude oil crude oil is useless but it has many useful components such as petrol, diesel and kerosene. All of the above are seperaeted out using fractional distillation.

Question 33

When is paper chromatography used

Answer 33

used to seperate out small quantities of substances from a solution

Question 34

Explain the process of paper chromatography (4)

Answer 34

the ink spots are carried up by the filter paper by the water the water is the mobile phase while the filter paper is the stationary phase after a certain time,the filter paper is taken out and a solvent front is marked (later used to calculate the Rf value) spots travel up the stationary phase at different rates, causing them to seperate out

Question 35

Which two factors are responsible for ow far the spots travel in paper chromatography (2)

Answer 35

mass solubility of the spots

Question 36

Equation for Rf value

Answer 36

Rf value = distance moved by teh spot from the baseline / distance moved by the solvent front from the baseline

Question 36

Equation for Rf value

Answer 36

Rf value = distance moved by teh spot from the baseline / distance moved by the solvent front from the baseline

Question 37

purpose of Rf values (2)

Answer 37

substances with Rf values can be referenced to determine unknown compounds Rf values of known substances can be compared to Rf values of unknown substance. If Rf values are same, substance is same

Question 38

How to use paper chromatography to test for purity

Answer 38

if substance is impure then there are more spots than would characteristically be expected