GCSE Chemistry States & separation questions by topic

Complete the sentences about the three states of matter.

1. (a)In a solid, the particles …[1]
2. (b)In a liquid, the particles …[1]
3. (c)In a gas, the particles …[1]

Bromoform melts at 8 °C and boils at 149 °C.

1. (a)State the physical state of bromoform at 3 °C.[1]
2. (b)State the physical state of bromoform at 20 °C.[1]
3. (c)State the physical state of bromoform at 160 °C.[1]

A student has four mixtures and needs to separate each one.

1. (a)Complete the table by naming one suitable technique for each mixture.[4]

A jewellery maker pours molten gold into a mould and it solidifies.

1. (a)Name the change of state taking place.[1]
2. (b)State whether the change takes in or gives out energy.[1]
3. (c)Explain why this is a physical change, not a chemical change.[2]

A factory leaves a clear, colourless liquid in a tank. Two samples are tested in the lab.

1. (a)Which sample is pure? Give a reason.[2]
2. (b)The liquid is advertised as “pure vinegar”. State what chemists mean by pure.[2]
3. (c)Give one everyday use of the word pure that differs from the chemistry meaning.[1]

A sealed bottle of water is moved from a freezer at −18 °C to a warm room at 22 °C and left until its temperature settles at 22 °C.

1. (a)State the physical state of the contents at −18 °C.[1]
2. (b)Name the change of state that happens as the bottle warms up, and state whether the change takes in or gives out energy.[2]
3. (c)Describe one difference in the movement of the particles before and after the change.[2]

A pharmacy shelf holds four products: a painkiller tablet, a bottle of distilled water, a bronze ornament and a cylinder of medical oxygen.

1. (a)Classify each product as a formulation or not a formulation.[2]
2. (b)Explain why bronze is a formulation.[2]
3. (c)Explain why distilled water is not a formulation.[2]

A student separates the components of a flower extract using paper chromatography.

1. (a)Name the stationary phase and the mobile phase in this experiment.[2]
2. (b)Explain why the substances in the extract separate into different spots.[2]
3. (c)The extract gives three spots. What does this show about the extract?[1]
4. (d)Explain why the start line is drawn in pencil.[1]

A class makes pure water from sea water in the laboratory using simple distillation.

1. (a)Describe how the apparatus works, naming the part where the vapour turns back into liquid.[3]
2. (b)State what is left in the distillation flask at the end.[1]
3. (c)Explain why simple distillation is not used to make drinking water on a large scale.[2]

Air is cooled to about −200 °C until it liquefies, then warmed slowly in a fractionating column.

1. (a)Nitrogen boils at −196 °C, argon at −186 °C and oxygen at −183 °C. State the order in which the gases boil off, giving a reason.[2]
2. (b)Explain why the column has a temperature gradient from bottom to top.[2]
3. (c)State one use of the oxygen fraction.[1]
4. (d)State the name of the process used to liquefy the air in the first place.[1]

Impure solid X melts gradually between 44 °C and 49 °C. Pure X is known to melt at 51 °C.

1. (a)Explain what the melting range shows about sample X.[2]
2. (b)The sample melts below 51 °C. Name this effect of impurities.[1]
3. (c)Describe how you would obtain a pure sample of X from the impure solid if X is soluble in water and its impurity is insoluble.[1]

A student claims: “Filtration is the better way to make drinking water from sea water, because filtration is much quicker than distillation.”

1. (a)Evaluate the student’s claim.[4]
2. (b)The student’s filtered sample still tastes salty. Explain why.[1]
3. (c)State one situation in which filtration is the correct choice of technique.[1]

A class distils blue copper sulfate solution, but the colourless distillate collected turns out to be tinted pale blue.

1. (a)Suggest what went wrong, and name one addition to the flask that reduces the risk.[2]
2. (b)State the purpose of anti-bumping granules.[1]
3. (c)Explain why the cold water should enter the condenser jacket at the bottom.[2]
4. (d)Describe one measurement that would confirm the collected water is pure.[1]

A heater supplies energy at a steady rate to a beaker of crushed ice at −20 °C.

1. (a)Sketch or describe how the thermometer reading changes until the water boils, and explain the shape.[4]
2. (b)Explain why the temperature does not rise during melting even though heating continues.[2]

A perfume contains ethanol (boiling point 78 °C), a fragrant oil (boiling point 205 °C) and water.

1. (a)Name the technique that would separate the fragrant oil from the perfume, and explain why it works.[3]
2. (b)During the separation, the column temperature at the outlet holds steady at 100 °C for a while. What is being collected at that moment, and why does the temperature hold steady?[2]
3. (c)Explain why filtering the perfume would achieve nothing.[1]

Two white solids, P and Q, look identical. P is pure acetanilide (melting point 114 °C); Q is acetanilide mixed with a small amount of an inert impurity.

1. (a)A student heats small samples of P and Q in separate melting-point apparatus. Describe the results that would distinguish them.[3]
2. (b)Q’s sample starts melting at 109 °C and finishes at 113 °C. Explain both observations in terms of particles.[2]
3. (c)State and explain one industrial context where knowing the purity of a solid matters.[1]

Substance Z is quoted as melting at exactly 114 °C. A sample thought to be Z melts gradually between 108 °C and 113 °C.

1. (a)Explain what the melting behaviour shows about the sample.[2]
2. (b)The sample is dissolved, filtered and crystallised twice more; the new crystals now melt sharply at 114 °C. Explain why recrystallisation improved the purity.[2]
3. (c)Explain, in terms of particles, why the melting range narrows as a solid becomes purer.[2]

A fermented wash contains ethanol, water, dissolved sugars and suspended yeast cells. A distillery wants pure ethanol and, separately, the yeast cells back.

1. (a)Outline a full separation plan that delivers both products, naming each technique and what it collects.[4]
2. (b)Explain why the filtration step must happen before the distillation step.[1]
3. (c)State the physical property that lets the final step separate ethanol from water.[1]