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Question 1
The diagrams below show three different mixtures. |
a) | Define the term 'mixture'.
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b) | Which of the diagrams above depicts a mixture of elements?
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c) | Which of the diagrams above depicts a mixture of compounds?
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d) | Which two of the following substances are mixtures? A air B water C magnesium chloride D oxygen E steel F methane
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e) | Substances in a mixture can be separated using different methods. Draw one line from each substance and mixture to the most appropriate method of separation.
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Question 2
Sand does not dissolve in water. A student wants to separate a mixture of sand and water. |
a) | Which method can the student use to separate the mixture of sand and water?
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b) | Draw and label a diagram of the apparatus that the student could use. In your drawing, indicate:
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c) | Explain why the same method cannot be used to separate a mixture of ethanol and water.
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Question 3
Water was separated from salt water by simple distillation in a school laboratory. |
a) | Use the words 'boils', 'cools', 'condenses' and 'water vapour' to explain how salt water can be distilled into pure water.
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b) | Suggest why it is not safe to drink the distilled water sample prepared in the school laboratory.
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c) | Describe how to obtain salt crystals from salt water by crystallisation.
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d) | Hexane and water are immiscible. Describe how separate samples of hexane and water can be obtained from a mixture of hexane and water.
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Question 4
A mixture of three liquids was fractionally distilled. The image below shows the apparatus used. |
a) | Explain the difference between a mixture and a compound.
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b) | The table below shows the boiling points of the three liquids in the mixture. |
Which liquid in the table would be the first to distil and be collected in the beaker?
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c) | Suggest what would happen to the temperature of the water as it flows through the condenser.
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d) | Describe how oxygen and nitrogen are obtained from liquid air by fractional distillation.
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Question 5
A student uses the apparatus below to separate water from a salt solution. |
a) | What is the name of the process used by the student? A simple distillation B filtration C fractional distillation D chromatography
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b) | What temperature would you expect the thermometer to show?
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c) | Describe how the process shown in the image produces pure water from salt solution.
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d) | Water obtained by distillation does not need to be sterilised and is safe to drink. Suggest why.
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Question 6
Substances are separated from a mixture using different methods. |
a) | Draw one line from each method of separation to the substance and mixture it would separate.
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b) | To make crude oil more useful, it is separated into different fractions with different uses. What is the name of the process used to separate crude oil into different fractions? A fractional distillation B simple distillation C cracking D crystallisation
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c) | Describe and explain how petrol is separated from the mixture of hydrocarbons in crude oil.
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Question 7
Paper chromatography is one method of testing the dyes present in cake icing. |
a) | Explain what happens during the process of chromatography.
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b) | Plan an investigation, using paper chromatography, to determine the Rf value for a blue food dye in a sample of cake icing. Rf= distance moved by solvent distance moved by substance Your plan should include the following apparatus:
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c) | The Rf value of the blue dye is 0.60. The distance moved by the blue dye is 5.7 cm. Calculate the distance moved by the solvent.
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Question 8
Food colourings are used to coat some chocolate sweets. Some of these food colourings are suspected of causing asthma and rashes in children. |
A scientist used chromatography to investigate whether the problem food colourings were used in two sweets, S and P. The results are shown in the image below. |
a) | How many food colourings are there in sweet P?
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b) | In chromatography, the Rf value can be calculated using the following equation:
Rf value = distance moved by the solventdistance moved by the colouring Which food colouring has a Rf value of 0.3? A food colouring 1 B food colouring 2 C food colouring 3 D food colouring 4
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c) | From the chromatogram, what conclusions can the scientist make about the colourings in sweets S and P?
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Question 9
A student has a mixture of three substances. The table below shows information about these substances. |
Describe how the student can separate the mixture to get pure samples of all three substances. Explain why each method of separation works.
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Question 10
Nitric acid (HNO3) can be used to neutralise sodium hydroxide (NaOH). Sodium nitrate (NaNO3) and water are made. |
a) | Write a balanced symbol equation for this reaction.
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b) | Describe how dry sodium nitrate crystals can be obtained from the sodium nitrate solution produced in this reaction.
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