Topic 2 - States Of Matter & Seperating/purifying Substances

Question 1

A substance is heated at a constant rate and its temperature is taken every minute.
During the heating, the substance undergoes one change of state.
The results are shown on the graph in Figure 5.
Explain the shape of the graph in terms of the changes in the movement and arrangement of
the particles as the substance is heated. (4)

Positive gradient AB - horizontal line BC - positive gradient CD

Answer 1

From B to C, graph is flat because particles in solid use energy to break out of lattice/particles become randomly arranged/turn from solid to liquid (1)
From A to B, graph rises because particles in solid are in a lattice (1) so vibrate more rapidly as temperature increases (1)
From C to D, graph rises because particles in liquid move past one another/randomly (1) particles move more rapidly as temperature increases (1)

Question 2

An ink is a mixture of coloured substances dissolved in water.
Changes of state between the 3 states of matter are shown below.
Explain why these changes are called physical changes rather than chemical changes. (2)

(Melting) (evaporating)
Solid → liquid → gas
Gas → liquid → solid
(Condensing) (freezing)

Answer 2

Physical changes do not result in the formation of a new substance (1)
Physical changes can be easily reversed (1)

Question 3

Describe the differences in the arrangement and movement of the particles in a solid and in
a liquid. (2)

Answer 3

In a solid, particles are regularly arranged/ in a liquid, they are randomly arranged (1)
In a solid, particles don’t move around (only vibrate)/in a liquid, particles move around (1)

Question 4

Here are five statements about ice and water.
Place ticks in boxes by the two statements that are correct. (2)

The molecules move faster in water than in ice
The molecules are more randomly arranged in ice than in water
The molecules start moving when wage becomes ice
The molecules are arranged regularly in ice but not in water
The molecules have more energy in ice than in water

Answer 4

The molecules move faster in water than in ice (1)

The molecules are arranged regularly in ice but not in water (1)

Question 5

Overhead power lines are made of aluminium with a steel core.
Figure 5 shows some properties of steel and aluminium.
Explain why the power lines are made of aluminium with a steel core rather than pure
aluminium. (2)

Steel = high strength 7.87 density
Aluminium = low strength 2.70 density

Answer 5

Aluminium has low strength/steel has high strength (1)
Steel is added to make the power line stronger (1)

Question 6

Which of the following substances will be a solid at 20 °C and will melt when placed in a
beaker of hot water at 80 °C? (1)

MP = 122 BP = 249
MP = -7 BP = 59
MP = 30 BP = 2403
MP = -32 BP = 27

Answer 6

MP = 30 BP = 2403

Question 7

The 3 states of matter are solid, liquid and gas.
Figure 2 shows the melting points and boiling points of four substances, W, X, Y and Z.
Using the information below:

give the letter of the substance that is a solid at 20 °C (1) …………………………
give the letter of a substance that is a liquid at 50 °C (1) ……………………….

W MP= -220 BP= -188
X MP= -101 BP= -34
Y MP= -7 BP=59
Z MP= 114 BP=184

Answer 7

Z (1)
Y (1)

Question 8

Potable water is water that is suitable for drinking.
River water can be treated to make it potable.
Chlorination, filtration and sedimentation are 3 of the processes involved in making the river water potable.
Which row shows these 3 processes in the order in which they are carried out? (1)

Chlorination Sedimentation Filtration
Chlorination Filtration Sedimentation
Sedimentation Filtration Chlorination
Sedimentation Chlorination Filtration

Answer 8

Sedimentation Filtration Chlorination

Question 9

State the reason why chlorine is added during water treatment. (1)

Answer 9

To kill bacteria/microorganisms

Question 10

Describe how sedimentation is carried out. (2)

Answer 10

Waste water is left in a tank to settle (1)
Sediment/particles/dirt falls to the bottom (1)

Question 11

Figure 5 shows the results of an analysis of a sample of potable water.
Explain why this sample of potable water is not the same as pure water. (2)

Chloride concentration = 60.70
Fluoride concentration = 0.24
Nitrate concentration = 24.90
Sulfate concentration = 71.40
Copper concentration = 0.05
Magnesium concentration = 9.10

Answer 11

The water contains ions/salts/any from above (1)
Pure water doesn’t contain ions/more than just water molecules/which are impurities (1)

Question 12

Samples of four inks, W, X, Y and Z, were separated using paper chromatography.
State what could be changed in the experiment to make the Rf value more accurate. (1)

Answer 12

Longer paper/different paper/medium

Question 13

In a chromatography experiment, ink sample Y did not move from the start line.
Explain a change to the experiment that would be needed to separate the dyes in ink sample Y. (2)

Answer 13

Use a different solvent (1)
So that the ink will dissolve (1)

Question 14

Use words from the box to complete the sentences. (3)
Simple distillation is used to separate a liquid from a …………………………………………………..
Vapour is cooled to form liquid. This process is called …………………………………………………..
The liquid collected in the beaker is known as the …………………………………………………..

Answer 14

Solid (1)
Condensation (1)
Distillate (1)

Question 15

Pure water collects in the beaker.
Explain how the apparatus will show that the liquid collected is pure water.

Answer 15

A thermometer (1)
Should show the boiling point of water (1)

Question 16

Waste water can be used to produce drinking water.
The processes used include sedimentation, filtration and chlorination.
What is sedimentation? (1)

the waste water is heated so the impurities evaporate
the waste water has an acid added to remove impurities
the impurities in the waste water settle to the bottom of their container
the impurities in the waste water are bleached

Answer 16

the impurities in the waste water settle to the bottom of their container

Question 17

State why waste water is filtered in water treatment. (1)

Answer 17

To remove solids/insoluble substances

Question 18

Describe how a sample of pure, dry sodium chloride crystals can be obtained from the
filtrate. (3)

Answer 18

Heat solution (to concentrate it) (1)
Leave solution in warm place to crystallise (1)
Scrape crystals from container/pat dry between filter papers (1)

Question 19

In a different method of obtaining nickel, the process produces a mixture of the liquids nickel
tetracarbonyl and iron pentacarbonyl.
The BP of nickel tetracarbonyl is 43°C.
The BP of iron pentacarbonyl is 103°C.
These two liquids mix together completely.
Describe the process used to separate these liquids. (3)

Answer 19

Fractional distillation (1)
Heat/boil (1)
nickel tetracarbonyl boils off first/is obtained from the top of the fractionating column (1)

Question 20

A sample of water was contaminated with a dissolved solid.
Devise a plan to separate pure water from this mixture, including a test to show that the water obtained is neutral. (6)

Answer 20

SEPARATION
• distillation
• solution in flask
• heat
• water evaporates
• water vapour into condenser
• cooling water jacket
• water vapour condensed back to liquid
• water collected in beaker
• solid remains in flask
• boiling point = 100°C

TEST
• take distilled water in a test tube
• add a few drops of neutral litmus/Universal Indicator
• correct neutral colour OR
• pH probe
• pH = 7

Question 21

A student set up the apparatus shown below to obtain pure water from sea water by distillation.

Explain how the water in sea water separates to produce the pure water in this
apparatus. (2) ………………….
Explain how the apparatus could be improved to increase the amount of pure water
collected from the same volume of sea water. (2) …………………..

Heat, conical flask, straw, delivery tube, seawater

Answer 21

Water boils/evaporates to form steam (1) steam condenses to form pure water (1)

Use a Liebig condenser/wrap delivery tube with cold cloth (1) to increase effectiveness of cooling/amount of condensation (1)

Question 22

In analysis, tests are carried out on solids dissolved in water.
Explain why it is important that the water used is pure. (2)

Answer 22

Pure water has no other ions present (1)
Ions may give a false/incorrect result (1)

Question 23

Explain how filter paper separates an insoluble solid from a liquid. (2)

Answer 23

Liquids pass through the paper (1)
Solids do not (1)

Question 24

Paper chromatography was used to try to separate the coloured substances in five food
colourings, V, W, X, Y and Z.
The paper was placed in a beaker with the bottom of the paper in the solvent.

Identify the stationary phase in this experiment. (1) …….…………

Give a reason why the spots of the food colourings must be above the level of the
solvent, when the paper is placed in the solvent. (1) ……………..

Answer 24

Water (1)
Otherwise the spots transfer into the solvent (1)

Question 25

Give the reason why a spot of food colouring hasn’t moved during the chromatography experiment. (1)

Answer 25

It’s insoluble in the solvent

Question 26

The steps needed to carry out the chromatography experiment are listed below.

1 leave the solvent to rise up the paper
2 put solvent in the beaker
3 draw a start line on the piece of paper
4 place the paper in the beaker
5 remove the paper when the solvent is near the top
6 put small spots of the food colourings on the start line
List the steps in the correct order. (2)

Answer 26

2 3 6 4 1 5

Question 27

An ink is a mixture of coloured substances dissolved in water.
Distillation can be used to separate water from ink. Cold water flows through the condenser.
The flask was heated with a Bunsen burner.

Give the name of an alternative piece of apparatus that could be used to heat the flask. (1)

Answer 27

Electric heater

Question 28

An ink is a mixture of coloured substances dissolved in water.
Which method is used to separate the coloured substances in the ink? (1)

Answer 28

Chromatography

Question 29

There is a mixture of the solids magnesium, titanium and magnesium chloride.
Titanium doesn’t react with dilute hydrochloric acid.
Suggest a simple method to separate titanium from the mixture.

Answer 29

Filter off the titanium (1)
Wash the titanium (1)

Question 30

Titanium is extracted from its ore in several stages.
In the first stage, titanium chloride is formed as a gas.
The gas is cooled to form liquid titanium chloride containing dissolved impurities.
Suggest how pure titanium chloride could be separated from the impurities. (1)

Answer 30

Simple distillation

Question 31

Paper chromatography was used to separate a mixture of blue and red inks. A spot of the mixture was placed on chromatography paper.
Give a reason why the start line is drawn in pencil rather than in ink. (1)

Answer 31

Pencil is insoluble in the solvent

Question 32

A mixture of two immiscible liquids can be separated by using… (1)

fractional distillation
a separating funnel
evaporation
filtration

Answer 32

a separating funnel

Question 33

Describe how oxygen and nitrogen are obtained from liquid air by fractional distillation. (3)

Answer 33

Liquid air enters fractionating column (1)
Warms/heats/boils (1)
Gaseous nitrogen is found in the top of the column (1)
Liquid is in the bottom of the column (1)

Question 34

Which of the following pairs of substances contains one substance that is soluble in water and one that is insoluble in water?

A aluminium nitrate and lead sulfate
B ammonium chloride and copper sulfate
C copper hydroxide and lead sulfate
D sodium hydroxide and potassium nitrate

Answer 34

aluminium nitrate and lead sulfate

Question 35

Barium chloride solution is used to test for the presence of sulfate ions in a solution.
When sulfate ions are present, insoluble barium sulfate is formed.
Describe the appearance of barium sulfate. (1)

Answer 35

White precipitate

Question 36

Complete the balanced equation for the reaction between barium chloride and potassium sulfate. (2)

Answer 36

BaCl2 + K2SO4 → BaSO4 + 2KCl

Question 37

Lead carbonate is an insoluble salt.
Describe how a pure, dry sample of solid lead carbonate can be obtained from sodium carbonate solution and lead nitrate solution. (3)

Answer 37

Mix/react sodium carbonate and lead carbonate (1)
Filter off the precipitate (1)
Wash the residue with distilled water/dry using filter paper (1)

Question 38

The method used to prepare a salt depends on its solubility in water.
Complete Figure 9 by writing whether the salt is
soluble or insoluble. (2)

ammonium chloride
lithium sulfate
magnesium carbonate

Answer 38

ammonium chloride = soluble
lithium sulfate = soluble
magnesium carbonate = insoluble

Question 39

The method used to make the lead sulfate is:
● pour 100 cm3 lead nitrate solution into a beaker
● add drops of sodium sulfate solution until a precipitate is seen
● allow the precipitate to settle to the bottom of the beaker
● pour off the liquid
● use a spatula to transfer the solid lead sulfate onto a filter paper
Explain two ways of improving this experimental method to increase the amount and quality of lead sulfate obtained from the same volume of lead nitrate solution. (4)

Answer 39

Add excess sodium sulfate solution rather than a few drops (1)
So more reaction occurs to form more lead sulfate (1)
Filter the reaction mixture rather than poor off the liquid (1)
So none of the lead sulphate is lost in separation (1)
Wash the lead sulphate (1)
So the impurities are removed (1)
Place the lead sulphate in an oven/warm place (1)
So the lead sulphate is dry (1)

Question 40

Ammonium nitrate is produced from ammonia and nitric acid on a large scale in industry.
Ammonium nitrate can also be made in the lab by titrating ammonia solution with dilute nitric acid.
NH3 + HNO3 → NH4NO3
Ammonium nitrate crystals can then be obtained by evaporating off some of the water from the solution.
Give 2 reasons why this laboratory method isn’t suitable for use on a large scale in industry. (2)

Answer 40

Volume of solution is too large for titration method (1)
Large volumes of liquid need to be heated and then allowed to crystallise (1)

Question 41

Hexane and water are immiscible.
Describe how separate samples of hexane and water can be obtained from a mixture of hexane and water. (2)

Answer 41

Use separating funnel (1)
Run off lower liquid (1)

Question 42

Nitrogen and oxygen are gases in air.
Describe how samples of nitrogen and oxygen can be obtained from air. (3)

Answer 42

Cool/liquify air (1)
Fractional distillation (1)
Allow to warm/heat (1)
Nitrogen obtained from the top of the column (1)
Oxygen obtained from the bottom of the column (1)

Question 43

Graphite is a form of the element carbon. Graphite is a giant molecular, covalent substance.
Use the structure and bonding in graphite to explain why it is able to be used as a lubricant and as a conductor of electricity. (6)

Answer 43

Carbon atoms joined by covalent bonds
Each carbon atom bonded to 3 others
Carbon atoms in hexagonal arrangement
Layers
Weak forces between layers
Layers can slide (hence lubricant)
Free electrons between layers
Free electrons can move
And carry current (hence conduction of electricity)