OCR GCSE Combined Science B (21st Century) Paper 6 June 2023 question paper

The combustion of fossil fuels for energy produces harmful substances.

Explain one problem caused by increased amounts of sulfur dioxide in the atmosphere.

Describe one method that is used to decrease the amount of harmful substances put into the atmosphere by petrol cars.

The combustion of fossil fuels produces carbon dioxide. Most scientists now accept that recent climate change can be explained by increased carbon dioxide emissions.

Fig. 1.1 shows the change in concentration of CO₂ in the atmosphere over time.

Fig. 1.2 shows the change in world carbon dioxide emissions from fossil fuels over time.

Fig. 1.3 shows the change in global average temperature over time.

Describe the trends in Fig. 1.1 and Fig. 1.2 and explain how this can be used with Fig. 1.3 to show that human activity is causing the global temperature to increase.

A company called Healthyfood make food colourings.

The diagram shows the label from one of their food colourings.

Healthyfood

Orange food colouring

All ingredients natural and tested

Ingredients: dye 1, dye 2, solvent

A representative for Healthyfood says that the food colouring is pure.

A scientist says that it is not pure.

Explain the different meanings of the word ‘pure’ used by the Healthyfood representative and the scientist.

Healthyfood representative........

Scientist........

The table shows the melting points of some substances.

Which two substances are chemically pure?

The dyes in the food colouring can be separated using paper chromatography.

The diagram shows the apparatus used to separate the dyes and the chromatogram that is produced.

Draw lines to connect each letter with its correct label.

Which property causes the dyes in the food colouring to separate?

Tick (✓) one box.

The chromatogram can be used to find the Rf values for the dyes.

Measure the distance moved by dye 1 and by the solvent.

Use a ruler.

Calculate the Rf value of dye 1.

Use this formula.

One type of reaction is called neutralisation.

An example of a neutralisation reaction is when magnesium hydroxide reacts with nitric acid.

Describe neutralisation by naming each type of compound in this reaction.

Neutralisation can also be described as the reaction between ions.

Give the formulae of the ions that are involved in neutralisation and the product of the reaction of these ions.

Ion from nitric acid........

Ion from magnesium hydroxide........

Product........

When some metals are added to acids, bubbles are seen in the solution.

Complete the word equation for the reaction between zinc and hydrochloric acid.

Explain why bubbles form very quickly when zinc is added to the acid but very slowly when lead is added to the acid.

Use ideas about electrons in your answer.

Crude oil is a mixture of different length hydrocarbon chains.

Explain how modern life is dependent on hydrocarbons from crude oil.

Cracking is used to turn the longer-chain hydrocarbons into more useful products.

Describe how the products of cracking are more useful than the long chain hydrocarbons.

When decane, C₁₀H₂₂, is cracked, one of the products is ethene, C₂H₄.

Complete the symbol equation to show the formula of the other product.

* The mixture of hydrocarbons in crude oil is separated using fractional distillation.

The diagram shows the apparatus used by industry.

Describe how crude oil is separated using fractional distillation and explain why the separation occurs.

Use ideas about the size of molecules and intermolecular forces.

Around 1800, Dalton stated that atoms are the smallest particles that exist.

The models show how the atomic model has developed further over time:

Draw lines to connect each scientist with how and why the model was changed.

Scientist
How model changed
Why model changed

The diameter of an atom is approximately 50 000 times bigger than its nucleus.

The diameter of an atom is approximately 1 × 10^–10 m.

Estimate the diameter of a nucleus.

Group 0 elements exist as single atoms and are very unreactive.

Why are Group 0 elements very unreactive?

Give two physical properties of Group 0 elements.

Group 1 elements react with water to form a metal hydroxide and hydrogen.

Complete the symbol equation for the reaction of sodium with water.

Complete the table by predicting the observations for the reaction of rubidium with water.

Alex plans to make a pure, dry sample of copper sulfate crystals.

Alex adds solid copper oxide to aqueous sulfuric acid in a beaker until no more solid reacts. This is the symbol equation for the reaction:

Why should there be some solid copper oxide left in the beaker?

Alex finds that the reaction is slow.

Give two ways in which Alex can make the reaction faster.

When the reaction has finished, Alex uses the contents of the beaker to make pure, dry crystals of copper sulfate.

Describe the method that Alex uses.

Alex used 20 cm³ of 0.5 mol / dm³ sulfuric acid. (c)

Calculate the number of moles of sulfuric acid used.

How many moles of copper sulfate are formed?

Use the symbol equation and your answer to (c)(i):

Calculate the mass of copper sulfate crystals formed.

The relative formula mass of the copper sulfate crystals is 249.6.

Use your answer to (c)(ii) and the relationship:

Give your answer to 1 decimal place.

This question is about exothermic and endothermic reactions.

Hydrogen reacts with oxygen to form water.

To observe the reaction, a platinum gauze is required. The diagram shows the energy profile for the reaction with and without a platinum gauze.

Why is this an example of an oxidation reaction?

State the role of the platinum gauze and explain why it causes the reaction to occur.

Role........

Explanation........

The table shows some bond energies.

Calculate the energy change for this reaction:

A student reads in a textbook:

‘When solid ammonium nitrate dissolves in water the reaction is endothermic.’

Describe an experiment the student could do and their expected results to confirm the statement in the box.

Complete the energy profile for ammonium nitrate dissolving in water.

Label the energy profile to show the:

• activation energy

• reactants

• products.

Use the equation:

The company has chosen to use copper to make saucepans.

Evaluate the company’s choice.

Use the table.

Suggest one other factor that should be considered by the company when deciding which material to use.

Companies also need to consider the life-cycle assessment of a product when comparing materials.

A life-cycle assessment analyses the environmental impact of each stage of a product’s lifetime.

One of the things considered during the manufacturing stage of the process is the use of the raw materials.

Describe two other resources which should be considered during the manufacturing stage.

Describe one other stage of a product’s lifetime which should be considered in a life-cycle assessment.

Compounds are bonded together ionically or covalently. Models are used to represent these compounds.

Sodium (electron arrangement 2.8.1) reacts with chlorine (electron arrangement 2.8.7) to form sodium chloride. Sodium chloride is bonded ionically.

Two models are shown to represent sodium chloride:

Describe one limitation of representing sodium chloride by each of these models.

Dot and cross model........

Explain how the ionic bond is formed in sodium chloride.

Use ideas about electrons and electrostatic forces in your answer.

Magnesium (electron arrangement 2.8.2) reacts with oxygen (electron arrangement 2.6) to form magnesium oxide.

Draw the dot and cross diagram for magnesium oxide.

Complete Table 9.2 by showing the 2-D model of propane.

All these models show the number of each atom and the order in which the atoms are joined together.

Describe one limitation of representing the structure of propane that is true for both the dot and cross model and the 2-D model.

The empirical formula shows the simplest ratio of atoms in a molecule.

What is the empirical formula of ethane?

Some elements form giant covalent structures.

Table 9.3 shows the structures of two allotropes of carbon.

Table 9.3

Complete Table 9.3 by showing the 2-D model for diamond.