OCR GCSE Chemistry B (21st Century) Paper 2 June 2023 question paper

Poly(ethene) is a polymer which forms when ethene monomers react together in an addition polymerisation reaction.

The structure of an ethene monomer and the repeating unit of poly(ethene) are shown in Fig. 1.1.

Ethene monomer
Repeating unit of poly(ethene)

Which statements are true only for an ethene monomer, which are true only for the repeating unit of poly(ethene) and which are true for both?

Tick (✓) one box in each row.

PVC is another addition polymer.

The structure of the repeating unit of PVC is shown in Fig. 1.2.

Draw the structure of a monomer of PVC.

Models are used to represent the structure of compounds.

Draw lines to connect each formula to the correct model.

Which formula contains an atom of a Group 17 (7) element?

Which formula contains an atom that is in both diamond and graphite?

Solid sodium chloride contains sodium ions, Na +, and chloride ions, C l –. (b)

Fig. 2.1 shows a three-dimensional model of how the ions are arranged in solid sodium chloride.

Calculate the total number of ions in the model in Fig. 2.1.

Which descriptions about the structure of sodium chloride are shown by the model in Fig. 2.1 and which are not ?

Tick (✓) one box in each row.

Fig. 2.2 shows a two-dimensional diagram of sodium chloride. One ion is labelled.

Label the other ions in Fig. 2.2.

Use the symbols Na + and C l –.

Crude oil is a mixture of hydrocarbons.

The table shows information about two hydrocarbons.

Complete the table.

The hydrocarbons shown in the table are alkanes.

The general formula for alkanes is C_nH_2n+2.

What is the formula for an alkane that contains 5 carbon atoms?

Explain why these molecules are hydrocarbons.

The alkanes from crude oil can be used in other processes to make more useful molecules.

Which process makes more useful molecules from alkanes?

Combustion Cracking Filtration Neutralisation

* Crude oil is separated into fractions in a fractionating column.

The diagram shows information about a fractionating column and some of the molecules in the fractions that leave the column.

Fractions OUT Number of carbon Boiling point (°C)

Explain why the molecules leave the column at different heights.

Use ideas about number of carbon atoms and boiling points in your answer.

Some cars use fuel cells as an energy source. Fuel cells can use methane or hydrogen as fuels.

The diagram shows the substances that go in and the waste products that come out of a methane fuel cell and a hydrogen fuel cell.

Methane fuel cell
Hydrogen fuel cell

Complete the symbol equations for the reactions in each fuel cell.

Use information from the diagram.

The table shows the sources of methane and hydrogen.

Explain the advantages to the environment of using hydrogen rather than methane in fuel cells in cars.

Use the information in the table and the diagram.

A mixture of hydrogen and oxygen is very flammable but does not explode until it is ignited by a flame.

Which statement explains why?

Tick (✓) one box.

The flame brings the gases closer together.

The flame provides activation energy for the reaction.

The flame takes energy in from the hydrogen and oxygen.

Jamal does an experiment to investigate the energy changes when solids A, B, C and D, dissolve in water.

The method for the experiment and some of the apparatus he uses is shown.

Name two pieces of measuring equipment Jamal needs to use in his experiment.

Which two variables does Jamal need to control in his experiment?

Tick (✓) two boxes.

The final temperature.

The mass of the solid.

The time taken to dissolve the solid.

The volume of water.

Table 5.1 shows Jamal’s results. Table 5.1

Jamal thinks that the temperature changes in his experiment are too small.

Which two changes could Jamal make to increase the temperature changes in his experiment?

Tick (✓) two boxes.

Add more solid.

Stir more slowly.

Use boiling water at the start.

Use less water.

Which two solids shown in Table 5.1 dissolve in an exothermic reaction?

Tick (✓) two boxes.

Explain your answer.

A B C D

Jamal measures the temperature change when solid E dissolves in water.

He repeats his experiment three times.

Table 5.2 shows his results.

Table 5.2

Calculate the mean temperature change when solid E dissolves.

Mia uses sunscreen on her skin when she is in the sun. The sunscreen contains nanoparticles. The nanoparticles block harmful radiation from the sun.

Mia talks about using nanoparticles.

Give two reasons why using nanoparticles may cause a risk to health.

Which statements about nanoparticles are true and which are false ?

Tick (✓) one box in each row.

The table shows some data about the diameter of nanoparticles A, B, C and D.

Put the nanoparticles A, B, C and D in order from largest to smallest.

Largest........

Smallest........

Mia makes a 3D model of nanoparticle B in the shape of a cube.

She makes each side of her model 2.10 cm long.

Calculate the volume of the model.

Give your answer to one decimal place.

Use this formula:

volume = h × w × d

Calculate the surface area of the model.

Use this formula:

surface area = 6 × (h × d)

Eve does an experiment to find out the rate of reaction when solid zinc reacts with dilute acid.

She adds the zinc to the dilute acid and measures the time taken to collect 10 cm³ of gas.

Complete the diagram by drawing and labelling the apparatus she needs to collect and measure 10 cm³ gas.

Eve repeats her experiment at different temperatures using zinc, copper, metal X and iron.

She adds the same amount of each metal and the same volume and concentration of acid each time.

Her results are shown in the table.

What conclusion can you make about the effect of changing the temperature on the rate of the reaction?

Explain your answer.

Suggest why no gas is collected when copper is used in the experiment.

Suggest the name of metal X.

Explain your answer.

Name........

Explanation........

* Eve says:

Write a method for Eve to use to find out if her idea is correct. Include in your answer:

• what variables to control and to change

• what results to expect.

Ammonia is made on an industrial scale by the reaction between nitrogen and hydrogen.

The equation to make ammonia is shown.

Which two statements explain why the atom economy of this reaction is 100%?

Tick (✓) two boxes.

All of the atoms in nitrogen and hydrogen are used to make ammonia.

All the substances involved in the reaction are gases.

The reaction makes only one product.

There are two nitrogen atoms on both sides of the equation.

Ammonia is used to make fertilisers.

Using fertilisers has both risks and benefits to the environment and to people.

Fertiliser from fields can get into rivers.

How does this cause a risk to the environment?

Give one benefit of using fertilisers.

Scientists use models to represent atoms. These models have changed over time.

Dalton’s model and a modern model of an atom are shown in the diagrams.

Give two differences between the modern model and Dalton’s model.

Which element is represented by the modern model in the diagram?

Explain your answer.

Use the Data Sheet.

Element........

Explanation........

Dalton used symbols for atoms to write formulae.

Each symbol represented a different type of atom.

Some of Dalton’s formulae are shown in the table.

Explain how Dalton’s formula for carbon dioxide agrees with its modern formula.

Give two reasons why Dalton’s formula for chlorine disagrees with its modern formula.

Ali works in a laboratory that tests food to make sure it is safe to eat.

He tests some sweets. The sweets are sold to shops in large boxes which each contain 100 packets of sweets.

Describe how Ali should choose sweets to test to make sure that his sample is representative.

Explain why it is important that the sample Ali tests is representative.

Ali uses paper chromatography to test two sweets, sweet 1 and sweet 2.

He also tests some samples of safe food colours, A, B, C and D.

The diagram shows Ali’s results.

Calculate the Rf value of food colour D.

Which safe food colours, A, B, C and D, are pure?

Explain your answer.

Food colours........

Explanation........

Which two safe food colours have been used to make sweet 2?

Tick (✓) two boxes.

Ali says that he cannot be sure that the food colours used in sweet 1 are safe.

Explain why Ali is correct.