IGCSE 2021 4CH1/1C January Edexcel Chemistry

Edexcel IGCSE Chemistry Past Papers and solutions.
Questions and Worked Solutions for IGCSE 2021 4CH1/1C January Paper 1 (Extended).

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This question is about states of matter.
(a) Use the words solid, liquid or gas to give the initial and final state of matter for each of the changes listed in the table.
The first one has been done for you.
(b) Particles in a solid are closely packed, arranged in a regular pattern and vibrate about fixed positions.
Describe the arrangement and movement of the particles in a gas
The table gives the melting and boiling points of four pure substances, W, X, Y and Z.
Use data from the table to answer the questions.
(a) (i) Which substance is a gas at 100°C?
(ii) Which substance is a liquid for the largest range of temperature?
(iii) Which substance is a liquid at 1000°C and a gas at 2000°C?
(b) Substance Y does not conduct electricity when solid but does conduct electricity when molten.
Give the type of bonding in substance Y.
(b) Substance Y does not conduct electricity when solid but does conduct electricity when molten.
Give the type of bonding in substance Y.
Lead nitrate and potassium iodide react to form the insoluble solid lead iodide. Crystals of lead nitrate and potassium iodide are placed at opposite ends of a container of water.
Solid lead iodide forms after several minutes.
The diagram shows the container at the start and after several minutes
(a) Name the two processes that occur before the solid lead iodide forms
(b) Explain why solid lead iodide takes less time to form when the reaction is repeated using water at a higher temperature.
(c) The formula for lead nitrate is Pb(NO₃)₂
(i) Give the number of different elements in lead nitrate.
(ii) Give the charge on the lead ion in Pb(NO₃)₂
(d) Complete the chemical equation for the reaction between lead nitrate and potassium iodide.
This question is about rusting.
(a) When iron rusts, it reacts with oxygen in the air.
A student uses the rusting of iron to find the percentage of oxygen in a sample of air.
The diagram shows the apparatus
These are the student’s results.
volume of air in conical flask and connecting tube = 265cm³
volume of air in gas syringe at start = 100cm³
volume of air in gas syringe at end = 25cm³
Calculate the percentage of oxygen in the sample of air using the student’s results
(b) (i) Cars are painted to prevent the iron in car bodies from rusting.
Explain how painting prevents the iron in car bodies from rusting
(ii) Some car manufacturers use paint containing tiny particles of zinc.
Explain how particles of zinc prevent iron in car bodies from rusting even when this paint is scratched.

This question is about the separation of mixtures.
(a) The box gives some methods used to separate mixtures
Complete the table by giving the correct method from the box for each separation.
Each method can be used once, more than once or not at all
(b) A student uses chromatography to analyse the composition of purple ink.
The diagram shows the student’s chromatogram at the end of the experiment.
(i) Explain which dyes are contained in the purple ink.
(ii) Explain which dye is least soluble in the solvent
(c) A different chromatography experiment is set up.
A spot of food colouring is placed on the start line.
A food dye in the colouring has an Rf value of 0.72
The distance between the start line and the solvent front is 120mm.
Calculate the distance the food dye moves from the start line
This question is about salts.
(a) When solutions of salts are mixed together, precipitates sometimes form.
The insoluble salt barium carbonate forms as a precipitate when solutions of the soluble salts ammonium carbonate and barium chloride react together.
When solutions of the soluble salts potassium chloride and magnesium sulfate are mixed, no precipitate forms.
Complete the table to show the results of mixing solutions of some soluble salts.
(b) A student has four unlabelled beakers, each containing a colourless solution of a different salt.
The four solutions are

potassium carbonate
potassium chloride
potassium iodide
sodium chloride
Describe a method to identify each solution.
Do not refer to safety in your answer

This question is about lithium oxide.
(a) The diagram shows the electron configurations of an atom of lithium and an atom of oxygen.
Describe the changes in electronic configuration when lithium and oxygen react to form lithium oxide, Li₂O
(b) Lithium oxide reacts with water to form lithium hydroxide as the only product.
A scientist uses this apparatus to measure the temperature change of the reaction.
This is the scientist’s method.

pour 100g of water into a polystyrene cup
record the temperature of the water
add the lithium oxide and stir the mixture
record the maximum temperature reached
The diagram shows the thermometer readings before and after adding the lithium oxide.
(i) Complete the table, giving all values to the nearest 0.1°C
(ii) Calculate the heat energy change in the reaction.
Give your answer to two significant figures.
(iii) In another experiment the scientist obtains these results
Calculate the molar enthalpy change in kJ/mol.
Include a sign in your answer
(iv) Give a reason why the scientist does the experiment in a polystyrene cup

This question is about the halogens.
(a) The table gives some information about the halogens.
Complete the table by predicting the physical state of astatine at room temperature and the colour of astatine
(b) Bromine has two isotopes with mass numbers 79 and 81
(i) The relative percentages of each isotope in a sample of bromine are
bromine-79 = 51.0%
bromine-81 = 49.0%
Calculate the relative atomic mass of this sample of bromine.
Give your answer to one decimal place
(ii) Give a reason why both isotopes of bromine have the same chemical properties
(c) A student investigates the reactivity of some halogens.
She uses these solutions of halogens and their halides.

bromine, chlorine and iodine
sodium bromide, sodium chloride and sodium iodide
She adds each halogen solution to each halide solution.
The table shows her results.
(i) Explain how these results show the order of reactivity of bromine, chlorine and iodine.
(ii) Suggest why the student does not need to add bromine solution to sodium bromide solution.
(iii) The ionic equation for the reaction between bromine and sodium iodide is Explain why this is a redox reaction

Propane is a hydrocarbon with the formula C₃H₈
(a) State why propane is a hydrocarbon
(b) (i) Name the poisonous gas that forms when propane is burned in a limited supply of air.
(ii) State why this gas is poisonous to humans.
(c) The diagram represents a molecule of propane.
Describe the forces of attraction between the atoms in a molecule of propane
(d) Propane can be produced by cracking.
An equation for cracking is
Explain why cracking is an important process in the oil industry.
(e) Propane reacts with bromine in the presence of ultraviolet radiation.
(i) Complete the equation for this reaction.
(ii) Give the name of this type of reaction. 10 This question is about alkanes.
(a) The graph shows the boiling points of several unbranched alkanes.
(i) Draw a curve of best fit.
(ii) Use the graph to find the boiling point of the alkane with 7 carbon atoms in its molecule.
Show on the graph how you obtain your answer
(iii) Explain the trend shown by the graph.
(b) The diagram represents two isomers with the formula C₅H₁₂
Explain why these compounds are isomers.
(c) (i) An alkane contains 82.8% carbon and 17.2% hydrogen by mass.
Show by calculation that the empirical formula of this alkane is C₂H₅
(ii) Deduce the molecular formula of this alkane
(d) The equation for the complete combustion of one mole of an alkane can be represented by
alkane + ZO₂ → XCO₂ + YH₂O
Complete combustion of one mole of the alkane produces 308g of carbon dioxide and 144g of water.
X, Y and Z are the numbers used to balance the equation.
Calculate the values of X, Y and Z.
[Mr of CO₂ = 44, Mr of H₂O = 18]
This question is about reactions that form gases.
(a) Hydrogen peroxide decomposes to form water and oxygen.
The equation for the reaction is
25.0cm³
of hydrogen peroxide solution are poured into a conical flask and 1.00g of solid manganese(IV) oxide is added.
Bubbles of oxygen gas are formed.
(i) Give the test for oxygen gas.
(ii) Describe a method to show that solid manganese(IV) oxide is a catalyst in this reaction and not a reactant.
(b) A student uses this apparatus to investigate the rate of the reaction between zinc and an excess of dilute hydrochloric acid.
This is the student’s method.

pour 50cm³ of dilute hydrochloric acid into a conical flask
add about 1.2g of zinc lumps
record the volume of hydrogen gas collected every 30s until no more hydrogen is collected
The graph shows the student’s results.
(i) Calculate the mean (average) rate of reaction, in cm³/s, in the first 120s.
(ii) The equation for the reaction between zinc and hydrochloric acid is
Use this equation and the particle collision theory to explain why the rate of reaction is greatest at the start of the reaction.
(iii) The student repeats the experiment at a higher temperature but keeps all other conditions the same.
On the grid, draw the curve you would expect to see in this experiment.
(iv) Explain why the rate of reaction is greater if the same mass of zinc powder is used instead of zinc lumps. All other conditions are kept the same.
(c) In another experiment, the student adds 0.55g of zinc to a solution containing 2.50 × 10⁻² moles of hydrochloric acid.
Use the equation to show that hydrochloric acid is in excess.

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