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Chemistry > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

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

A

What is changed

always x axis on a graph

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2
Q

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

A

what is measured

always y axis on a graph

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3
Q

Define control variable

A

factor(s) which are controlled during the investigation

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4
Q

which apparatus is used to measure time

A

stopwatch

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5
Q

Which apparatus is used to measure temperature

A

thermometer

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6
Q

Which apparatus is used to measure mass

A

mass balance

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7
Q

Define SI units

A

standardised units for measuring

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8
Q

Name the unit and symbol for electric current (2)

A

Unit: ampere

symbol: A

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9
Q

1L is also equal to? (2)

A

1dm^3

1000cm^3

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10
Q

Purpose of measuring cylinder

A

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

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11
Q

Purpose of pipette

A

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

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12
Q

Purpose of burette (3)

A

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

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13
Q

Define precise results

A

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

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14
Q

Define accurate results

A

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

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15
Q

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

A

filtration

fractional distillation

crystallisation

Distillation

Paper chromatography

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16
Q

Explain filtration (4)

A

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

17
Q

Explain evaporation (2)

A

used to seperate soluble solid from a liquid

liquid is evaporated off to leave behind the soluble solid

18
Q

Define pure substance

A

having only one type of particle

19
Q

Define impure substance

A

has more than one type of particle

20
Q

Relationship between melting/boiling point and purity (2)

A

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

21
Q

Relationship between melting/boiling point and impurity (2)

A

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

22
Q

Impure solids have a lower melting point than the pure solid

True or False

A

true

23
Q

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

True or False

A

true

24
Q

where and Why is purity important? (2)

A

important in food and pharmaceutical industries

any impurities could have potential lethal side effects

25
Q

Explain crystallisation (3)

A

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.

26
Q

What is distillation used to seperate

A

used to seperate a liquid with a soluble solid

27
Q

When is distillation used over evaporation

A

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

28
Q

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

A

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

29
Q

Explain the process of distillation (5)

A

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

30
Q

When is fractional distillation used (2)

A

used to seperate more complex liquid mixtures

used when the different in boiling points of the seperate components is rougly 25degrees

31
Q

Explain process of fractional distillation (5)

A

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

32
Q

Use of fractional distillation in industry

A

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.

33
Q

When is paper chromatography used

A

used to seperate out small quantities of substances from a solution

34
Q

Explain the process of paper chromatography (4)

A

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

35
Q

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

A

mass

solubility of the spots

36
Q

Equation for Rf value

A

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

36
Q

Equation for Rf value

A

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

37
Q

purpose of Rf values (2)

A

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

38
Q

How to use paper chromatography to test for purity

A

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

Chemistry (11 decks)

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