Question 1
The statement that best describes an element is:
A.
a substance made from two or more types of atom in a fixed ratio
B.
a substance containing different components that are not chemically bonded
C.
a substance made from one type of atom that cannot be chemically broken down
D.
a substance that can be separated into simpler substances by filtration
Question 2
The kinetic molecular description of a liquid is:
A.
particles close together and moving past one another
B.
particles close together and fixed in regular positions only
C.
particles far apart and vibrating about fixed positions
D.
particles far apart and strongly attracted to fixed neighbours
Question 3
A laboratory freezer is at . The temperature on the Kelvin scale is:
A.
B.
C.
D.
Question 4
The particle diagram that represents a pure compound is:
A.
B.
C.
D.
Question 5
A mixture contains sand and sodium chloride. The sodium chloride must be recovered as dry crystals. The most suitable sequence is:
A.
add water, evaporate the mixture, then filter
B.
filter the dry mixture, then evaporate the residue
C.
distil the dry mixture, then collect the distillate
D.
add water, filter, evaporate the filtrate
Question 6
The meaning of the state symbol in is:
A.
sodium chloride is dissolved in water
B.
sodium chloride is a gas mixed with water vapour
C.
sodium chloride is an insoluble solid suspended in water
D.
sodium chloride is molten
Question 7
Frost forms on a cold surface when water vapour changes directly to solid ice. The name and energy change for this process are:
A.
condensation; exothermic
B.
sublimation; endothermic
C.
freezing; endothermic
D.
deposition; exothermic
Question 8
The diagram shows particle models for three samples, A, B, and C. Empty circles and ones with a dot inside represent different elements, and joined particles represent chemically bonded atoms.
Identify which sample represents an element, a compound and a mixture.
[3]
Question 9
Calcium carbonate reacts with hydrochloric acid to form calcium chloride solution, carbon dioxide and water.
Complete the equation by adding state symbols.
[3]
Question 10
Brass contains copper and zinc. The reason brass is classified as a mixture rather than a compound is:
A.
it contains only metallic elements
B.
its particles have no attractions between them
C.
it can be chemically decomposed into simpler elements
D.
its composition can vary over a range
Question 11
A paper chromatogram is produced using ethanol as the solvent. Spot Y has travelled further than spot X from the baseline. The best conclusion is:
A.
X is more soluble in ethanol than Y
B.
X and Y must be the same pure substance
C.
Y has a greater attraction to the mobile phase than X
D.
Y has a greater attraction to the stationary phase than X
Question 12
A solid product begins to melt at and is completely liquid at . The best inference is:
A.
the sample is an element because compounds cannot melt
B.
the sample is boiling because the temperature is increasing
C.
the sample is pure because it has a fixed melting range
D.
the sample is impure because it melts over a range
Question 13
Two samples of the same gas contain the same number of particles. Sample P is at and sample Q is at . The ratio of the average kinetic energy of particles in Q to that in P is:
A.
B.
C.
D.
Question 14
A student is given a solid mixture of sand and sodium chloride. Sodium chloride is soluble in water and sand is insoluble in water.
Outline a method to obtain dry sodium chloride from the mixture.
[4]
Question 15
A pure solid is heated at constant pressure. The graph shows how its temperature changes with time.
State the region where melting occurs.
[1]
Explain why the temperature remains constant during the melting region although energy is being supplied.
[2]
Identify the physical state or states present in the boiling region.
[1]
Question 16
A sample of ethanol is cooled from to .
Calculate the final temperature in kelvin.
[1]
Calculate the temperature change in kelvin.
[1]
State how the average kinetic energy of the ethanol particles changes during the cooling within one state.
[1]
Question 17
A paper chromatogram is produced from a sample of black ink using water as the solvent.
Identify the mobile phase and the stationary phase.
[2]
Explain why the ink separates into several spots.
[2]
Question 18
A student purified an impure sample of a solid organic compound by recrystallization. Melting point data were recorded before and after recrystallization and compared with a reference value.
Material | Melting point / |
|---|---|
Impure sample (before recrystallization) | 128.5–133.8 |
Recrystallized sample | 135.7–136.3 |
Reference value | 136.4 |
Identify which sample has the highest purity using the data.
[1]
Explain why the impure sample melts over a wider temperature range than the reference sample.
[2]
Suggest one improvement to the recrystallization method that could increase the purity of the crystals.
[1]
Question 19
A food dye mixture and three pure reference dyes were analysed by paper chromatography using the same solvent.
Sample | Lower spot / cm | Upper spot / cm | Solvent front / cm |
|---|---|---|---|
Reference dye 1 | 1.2 | — | 6.0 |
Reference dye 2 | 2.4 | — | 6.0 |
Reference dye 3 | 3.6 | — | 6.0 |
Unknown sample | 2.4 | 3.6 | 6.0 |
Calculate the value for the spot in the unknown mixture that travelled when the solvent front travelled .
[1]
Deduce whether the unknown sample is a pure substance or a mixture.
[1]
Explain why one component of the mixture travelled further up the paper than the other.
[2]
Question 20
Three particle diagrams show the same substance in different physical states at the same pressure.
Identify the diagram that represents a gas.
[1]
State one feature of the particle model that explains why gases are much more compressible than liquids.
[1]
Compare the particle motion and macroscopic shape of a solid and a liquid.
[2]
Question 21
A pure substance is heated at constant pressure. The first horizontal section of its heating curve represents melting. The statement that describes the particles during this section is:
A.
average kinetic energy is constant while particle separation increases
B.
average kinetic energy decreases while bonds within particles break
C.
average kinetic energy increases while potential energy is constant
D.
average kinetic energy and temperature both increase steadily
Question 22
Brass contains copper and zinc. Different samples of brass may contain different percentages of zinc, and the properties of brass change with composition.
Discuss why brass is generally classified as a mixture rather than a compound.
[4]
Question 23
Both evaporation and boiling are examples of vaporization.
Distinguish evaporation from boiling in terms of where and when each process occurs.
[3]
Question 24
A sample of steam is cooled at constant pressure until ice is formed.
Identify the change of state occurring at the first horizontal region.
[1]
Explain why energy is released to the surroundings during this change of state.
[2]
State what happens to the average kinetic energy of the particles during the first horizontal region.
[1]
Question 25
A sealed syringe contains air. The outlet is blocked and the plunger is pushed in slowly.
Explain, using the kinetic molecular theory, why the gas can be compressed.
[2]
State how the motion of the gas particles is described by the kinetic molecular theory.
[1]
Question 26
A mixture of two miscible liquids was separated by simple distillation. The temperature at the top of the distillation apparatus was recorded as distillate was collected.
State the boiling point of the first liquid collected from the graph.
[1]
Explain why the temperature remains almost constant while the first liquid is being collected.
[2]
Suggest why simple distillation is suitable for this mixture.
[1]
Question 27
A pure solid was heated at a constant rate. The temperature of the sample was recorded until the sample had completely melted.
Identify the melting point of the substance from the graph.
[1]
Convert this melting point to kelvin.
[1]
Explain, using the kinetic molecular theory, why the temperature is constant during the plateau.
[2]
Question 28
A solid mixture contains iron filings, sand and sodium chloride. Some physical properties of the components are shown.
Component | Attracted by magnet | Soluble in water |
|---|---|---|
Iron filings | Yes | No |
Sand | No | No |
Sodium chloride | No | Yes |
Identify the component that can be removed first using a magnet.
[1]
After adding water and filtering, state the residue and the filtrate.
[2]
Suggest how solid sodium chloride can be obtained from the filtrate.
[1]
Question 29
A reaction mixture contains a desired solid product, an insoluble excess reactant and a soluble coloured impurity. The desired product is much more soluble in hot ethanol than in cold ethanol. Ethanol is flammable.
Evaluate a suitable purification method for obtaining the desired product as safely as possible.
[4]
Question 30
A student measures the melting range of two samples of the same organic solid using a melting point apparatus. The accepted melting point of the pure solid is .
Sample | Melting starts / | Melting ends / |
|---|---|---|
X | 121.7 | 122.2 |
Y | 116.8 | 119.8 |
State which sample is purer.
[1]
Explain how the melting range provides evidence for your answer.
[2]
State the temperature scale used in thermodynamic temperature measurements.
[1]
Question 31
Bronze samples with different compositions were prepared from copper and tin. Their melting behaviour and hardness were measured.
Sample | Tin / % by mass | Melting range / | Hardness / arbitrary units |
|---|---|---|---|
A | 5 | 995–1020 | 70 |
B | 10 | 970–1000 | 85 |
C | 15 | 930–970 | 100 |
D | 20 | 890–940 | 115 |
Use the data to justify classifying bronze as a mixture rather than a compound.
[2]
Compare the particle-level description of a compound with that of the bronze samples.
[1]
Explain why the presence of metallic bonding in bronze does not by itself make bronze a compound.
[1]
Question 32
Two samples of the same molecular substance were cooled from the liquid state under identical conditions. One sample was pure and the other contained a soluble impurity.
State the freezing point of the pure sample from the graph.
[1]
Describe two differences between the cooling curves of the pure and impure samples during freezing.
[2]
Evaluate which curve provides stronger evidence for a pure substance, using the kinetic molecular theory.
[2]
Question 33
An unknown ink was analysed by paper chromatography using two different solvents. Reference dyes were run on the same chromatograms.
Spot | Solvent 1 / cm | Solvent 2 / cm |
|---|---|---|
Solvent front | 7.5 | 7.5 |
Unknown spot 1 | 2.5 | 1.0 |
Unknown spot 2 | 4.5 | 6.0 |
Reference dye B | 2.5 | 1.0 |
Reference dye C | 3.5 | 3.0 |
Reference dye D | 4.5 | 6.0 |
For solvent 1, calculate the value of the unknown spot that travelled when the solvent front travelled .
[1]
Use the chromatographic data to identify the two reference dyes present in the unknown ink.
[2]
Suggest which solvent is more suitable for confirming the composition of the unknown ink and justify your answer.
[2]
Question 34
A pure liquid was heated at a constant rate until it became a gas. A heating curve was obtained.
Identify the change of state occurring during the horizontal plateau.
[1]
Explain why the temperature does not increase during this plateau even though heating continues.
[2]
Compare the arrangement and motion of particles before and after the plateau.
[2]
Question 35
A laboratory mixture contains sodium chloride, sand and a small amount of a coloured soluble dye. The mixture is treated with water before separation.
Substance | After stirring with water | After filtration | On gentle heating of filtrate |
|---|---|---|---|
Sand | Insoluble; remains as solid grains | Retained on filter paper | No change |
Sodium chloride | Soluble; dissolves in water | Passes through filter paper in solution | Water can be removed by gentle heating |
Dye | Soluble; gives a coloured solution | Passes through filter paper in solution | Water can be removed by gentle heating |
The mixture is stirred with water and then filtered.
I.
Distinguish between a compound and the original mixture in terms of bonding and composition.
[2]
II.
Identify the residue and the filtrate after filtration, giving a reason for each.
[2]
Explain how dry sodium chloride could be obtained from the filtrate after first removing the dye by chromatography.
[2]
Evaluate whether filtration alone is sufficient to separate all three components of the original mixture.
[2]
Question 36
A blue aqueous solution contains a dissolved, non-volatile salt. A student wants to obtain a sample of pure water and also recover the solid salt.
Distillation is used first.
I.
Identify the distillate and the residue after distillation.
[2]
II.
Explain why filtration would not separate the salt from the water in the original solution.
[2]
Explain two features of the distillation apparatus that help obtain liquid water safely and efficiently.
[2]
Evaluate whether evaporation to dryness would be a suitable alternative if both pure water and solid salt are required.
[1]
Question 37
A gas-filled syringe and a water-filled syringe are each sealed and pushed with the same force. The gas syringe is compressed much more than the water syringe.
Use the kinetic molecular theory to compare the contents of the two syringes.
I.
Compare the arrangement and motion of particles in a liquid with those in a gas.
[2]
II.
Explain why the gas is much more compressible than the water.
[2]
Explain why the smell of a volatile liquid spreads faster in a warm room than in a cold room.
[2]
Dry ice, solid , changes directly to at room temperature. State the name of this change of state and whether it is endothermic or exothermic.
[1]
Question 38
The average kinetic energy of particles in a gas sample was considered at different temperatures. The relationship was plotted using both Celsius and Kelvin temperature scales.
Temperature / | Temperature / K | Relative average kinetic energy / a.u. |
|---|---|---|
-273.15 | 0.00 | 0.00 |
0.00 | 273.15 | 0.91 |
26.85 | 300.00 | 1.00 |
100.00 | 373.15 | 1.24 |
326.85 | 600.00 | 2.00 |
Convert to kelvin.
[1]
Deduce the ratio of the average kinetic energy at to that at .
[1]
Explain why kelvin temperature, rather than Celsius temperature, is proportional to average kinetic energy.
[3]
Question 39
A reaction produced an impure solid product mixed with a small amount of insoluble solid and a soluble impurity. Three possible recrystallization solvents were tested.
Measurement | Solvent A / g per 100 g | Solvent B / g per 100 g | Solvent C / g per 100 g | Melting range / |
|---|---|---|---|---|
Desired product at | 1.8 | 0.1 | 0.9 | — |
Desired product at | 5.8 | 8.5 | 1.5 | — |
Soluble impurity at | 0.7 | 6.8 | 0.3 | — |
Soluble impurity at | 1.0 | 7.4 | 0.4 | — |
Crude product | — | — | — | 125–131 |
Purified product | — | — | — | 132–133 |
Reference product | — | — | — | 133–134 |
Identify the most suitable solvent for recrystallizing the desired product, using the solubility data.
[1]
Outline two steps needed after dissolving the crude product in the minimum volume of hot solvent.
[2]
Evaluate whether the purification was successful using the melting range data.
[2]
Question 40
A pure sample and an impure sample of the same solid organic substance are heated separately at a constant rate.
Consider the heating curve for the pure sample.
I.
Identify the region of the pure sample curve where both solid and liquid are present.
[1]
II.
Explain, using the kinetic molecular theory, why the temperature remains almost constant in this region even though heating continues.
[2]
Compare the melting behaviour of the pure and impure samples and explain how this can be used to assess purity.
[2]
Discuss the particle-level changes during melting and during boiling.
[3]
Question 41
Four particle diagrams represent different samples of matter. Circles with different shading represent atoms of different elements; circles touching represent bonded particles.
Use the particle diagrams to classify the samples.
I.
Identify one diagram that represents an element and one diagram that represents a compound.
[2]
II.
Distinguish between the homogeneous and heterogeneous mixtures shown in the diagrams.
[2]
Explain why an alloy is generally considered to be a mixture rather than a compound, even though metallic bonding may be present.
[2]
Discuss two pieces of experimental evidence that could help decide whether a clear colourless liquid is a pure compound or a homogeneous mixture.
[2]
Question 42
Two sealed samples of the same gas are at different temperatures. Sample X is at and sample Y is at .
Convert and compare the temperatures.
I.
Convert the temperature of sample X to kelvin.
[1]
II.
Explain why the average kinetic energy of particles in sample Y is greater than in sample X.
[2]
A student states that particles at have twice the average kinetic energy of particles at . Evaluate this statement.
[2]
Discuss why the temperature of a pure liquid remains constant during boiling at constant pressure.
[2]
Question 43
Crude crystals of a solid product contain two impurities: an insoluble solid and a soluble coloured impurity. The desired product is much more soluble in hot water than in cold water.
Material | Solubility at / g per 100 mL H₂O | Solubility at / g per 100 mL H₂O | Melting point / |
|---|---|---|---|
Accepted pure product | 1 | 25 | 123 |
Insoluble solid impurity | <0.1 | <0.1 | — |
Soluble coloured impurity | 8 | 35 | — |
Crude crystals | — | — | 116–120 |
Recrystallized crystals | — | — | 122–123 |
A student plans to purify the crude crystals by recrystallization.
I.
Explain why water is a suitable recrystallization solvent for the desired product.
[2]
II.
Outline the key steps needed to obtain purer dry crystals.
[3]
Evaluate how melting point data could be used to judge whether the recrystallization was successful.
[2]
Explain why some soluble impurity may remain in the final crystals if the crystals are not washed correctly.
[1]
Question 44
Calcium carbonate reacts with hydrochloric acid to produce carbon dioxide gas. The gas is collected in a gas syringe.
Use state symbols to represent the reaction.
I.
Write a balanced equation for the reaction, including state symbols.
[2]
II.
Explain the difference between the symbols and using examples from the equation.
[2]
Explain why the carbon dioxide fills the syringe and can be compressed.
[2]
A student claims that the decreasing mass of the flask during the experiment shows that matter is destroyed. Evaluate this claim.
[2]
Question 45
The graph shows the cooling of a pure substance from gas to solid at constant pressure.
Interpret the labelled regions on the cooling curve.
I.
Identify the two changes of state that occur in the horizontal regions during cooling.
[2]
II.
Explain why the horizontal regions are exothermic even though the temperature does not decrease during each region.
[2]
Compare and contrast boiling and evaporation at the particle level.
[2]
Discuss how the particle arrangement and motion change as the substance cools from liquid to solid.
[2]
Question 46
Water can condense from steam in a condenser. In a different process, liquid water can be decomposed by electrolysis into hydrogen and oxygen gases.
Compare condensation of steam with electrolysis of water.
I.
Explain why condensation is a physical change but electrolysis is a chemical change.
[2]
II.
Write the equation for electrolysis of water, including state symbols.
[2]
Discuss why water is classified as a compound rather than a mixture of hydrogen and oxygen.
[2]
Evaluate the usefulness and one limitation of particle diagrams for modelling these two processes.
[2]
Question 47
A black ink is analysed by paper chromatography using two different solvents.
Spot position | Solvent 1 distance from baseline / cm | Solvent 2 distance from baseline / cm |
|---|---|---|
Lowest spot | 0.8 | 2.5 |
Middle spot | 1.3 | 5.0 |
Highest spot | 1.8 | 7.5 |
Solvent front | 10.0 | 10.0 |
Interpret the chromatograms.
I.
Explain why the ink is classified as a mixture rather than a pure substance.
[2]
II.
Explain why different dyes in the ink travel different distances on the paper.
[2]
Evaluate which solvent is more suitable for separating the dyes in the ink.
[2]
Discuss one limitation of using this chromatogram alone to decide whether the ink contains a particular named dye.
[2]
Question 48
A homogeneous liquid mixture contains two miscible volatile liquids and a small amount of dissolved solid. The boiling points of the two liquids are well separated. One liquid is flammable.
Component | Type in mixture | Boiling point / | Miscible with other liquid? | Flammable? |
|---|---|---|---|---|
Liquid A | volatile liquid | 56 | yes | yes |
Liquid B | volatile liquid | 100 | yes | no |
Dissolved solid | non-volatile solid | — | n/a | no |
A separation sequence is proposed.
I.
Explain why filtration is not the first suitable method for separating this homogeneous mixture.
[2]
II.
Suggest a separation method for the two volatile liquids and justify it using the data.
[2]
Describe how the dissolved solid could be recovered after the liquids have been removed.
[2]
Evaluate two practical factors, other than separation efficiency, that should influence the choice of method.
[2]
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