States of Matter & MixturesEdexcel GCSE Chemistry: Topic test

20 questions, 54 marks

Edexcel GCSE Chemistry

States of Matter & Mixtures topic test

Total 54 marks

Name

Class

Date

1
A technician removes a sealed flask of liquid nitrogen from a cold store and leaves it on the open bench at room temperature. Over the next few minutes, the liquid nitrogen boils steadily, and colourless nitrogen gas escapes from the neck of the flask until the liquid has completely disappeared. (The boiling point of nitrogen is -196 degrees Celsius.)
(a)
Which row correctly describes the arrangement and movement of particles in the liquid nitrogen before it has fully boiled away?
[1 mark]
AParticles are close together but arranged randomly, and move around, sliding past one another
BParticles are held in a fixed, regular arrangement and only vibrate about fixed positions
CParticles are far apart and move rapidly in random directions
DParticles are far apart, with no forces of attraction between them, and remain stationary
(b)
Room temperature is far above nitrogen's boiling point of -196 degrees Celsius. What is the correct name for the change of state occurring throughout the liquid nitrogen in this situation?
[1 mark]
ACondensation
BBoiling
CSublimation
DFreezing
(c)
Explain, in terms of particle energy, why the nitrogen boils so rapidly at room temperature, whereas water at room temperature does not boil at all.
[2 marks]
Total for question 1: 4 marks
2
A geologist collects a sample of muddy river water containing fine suspended soil particles and dissolved mineral salts. She first pours the sample through a filter paper in a funnel to remove the soil, then wants to obtain a solid sample of the dissolved salts from the remaining clear liquid.
(a)
Which technique should the geologist use to separate the insoluble soil particles from the water?
[1 mark]
ACrystallisation
BFractional distillation
CFiltration
DPaper chromatography
(b)
Which technique should the geologist use to obtain solid dissolved salts from the clear filtrate?
[1 mark]
AFiltration
BCrystallisation
CPaper chromatography
DFractional distillation
(c)
Describe, in terms of particle size, how filtration separates the insoluble soil particles from the water.
[2 marks]
Total for question 2: 4 marks
3
A student is told that mercury has a melting point of -39 degrees Celsius and a boiling point of 357 degrees Celsius, and is asked to predict its physical state at various temperatures, including a very cold winter's day at -50 degrees Celsius and inside a thermometer at room temperature (20 degrees Celsius).
(a)
Predict the physical state of mercury at -50 degrees Celsius and at 20 degrees Celsius, justifying each answer.
[3 marks]
(b)
Explain, in terms of particle arrangement, movement and energy, what happens to mercury's particles as liquid mercury at room temperature is cooled down to -50 degrees Celsius and freezes into a solid.
[4 marks]
Total for question 3: 7 marks
4
A chemist has a mixture of ethanol (boiling point 78 degrees Celsius) and water (boiling point 100 degrees Celsius) produced during a fermentation process, and wants both to explain the particle behaviour behind their different boiling points and to separate the mixture into its two pure components using laboratory distillation apparatus.
(a)
Explain, in terms of particle arrangement, movement, energy and forces of attraction, why ethanol has a lower boiling point than water even though both are liquids at room temperature.
[6 marks]
(b)
Describe how distillation could be used to separate this mixture of ethanol and water into its two pure components, explaining how the difference in boiling points allows the separation to work.
[6 marks]
Total for question 4: 12 marks
5
A technician gently heats a few dark purple-grey crystals of solid iodine in a test tube. Without ever appearing to melt into a liquid, the iodine turns directly into a purple vapour, which then forms iodine crystals again on the cooler upper part of the tube.
(a)
What is the correct name for the change of state as the solid iodine crystals turn directly into a purple vapour?
[1 mark]
ASublimation
BMelting
CBoiling
DEvaporation
(b)
What is the correct name for the change of state as the purple vapour turns back into iodine crystals on the cooler glass?
[1 mark]
ACondensation
BDeposition
CFreezing
DEvaporation
(c)
Explain, in terms of forces of attraction and particle energy, why solid iodine can turn directly into a gas without forming a liquid first.
[2 marks]
Total for question 5: 4 marks
6
A student runs a paper chromatography experiment on the dye from a green felt-tip pen. A spot of the dye is placed near the bottom of a strip of chromatography paper, which is then dipped into a solvent. As the solvent rises up the paper, the green spot separates into a blue spot and a yellow spot.
(a)
What does this result show about the dye in the green felt-tip pen?
[1 mark]
AIt has been contaminated during the experiment
BIt is an insoluble solid
CIt is a mixture of at least two soluble coloured substances
DIt is a pure substance
(b)
In this chromatography experiment, what is the stationary phase and what is the mobile phase?
[1 mark]
AStationary phase: the solvent; mobile phase: the paper
BStationary phase: the dye; mobile phase: the paper
CStationary phase: the paper; mobile phase: the dye
DStationary phase: the paper; mobile phase: the solvent
(c)
Explain how paper chromatography separates the different coloured substances in the dye.
[2 marks]
Total for question 6: 4 marks
7
A quality-control technician measures the melting behaviour of two white powders, P and Q, both sold as 'pure' food additives. Powder P melts sharply at exactly 158 degrees Celsius. Powder Q begins to melt at 148 degrees Celsius and is not completely melted until 163 degrees Celsius.
(a)
State which powder, P or Q, is a pure substance, and explain how the melting data supports your answer.
[3 marks]
(b)
Explain, in terms of the particles present, why a mixture such as powder Q melts over a range of temperatures rather than at one sharp temperature like a pure substance.
[4 marks]
Total for question 7: 7 marks
8
A quality-control chemist receives a sample of potassium nitrate fertiliser contaminated with insoluble chalk dust. She dissolves the sample in warm water, filters off the chalk, and then heats the remaining potassium nitrate solution gently to evaporate some of the water before leaving it to cool and crystallise.
(a)
Describe the steps needed to obtain pure, dry crystals of potassium nitrate from this contaminated sample, explaining the purpose of each step.
[6 marks]
(b)
Explain, in terms of particle arrangement, movement and energy, what happens to the water molecules as the solution is heated and evaporates, and what happens to the potassium nitrate particles as the solution cools and crystals form.
[6 marks]
Total for question 8: 12 marks

End of questions