OCR GCSE Combined Science B (21st Century) Paper 2 November 2021 question paper

Mendeleev organised elements into the first Periodic Table.

What information did Mendeleev use to help him decide the order of the elements?

Tick (✓) one box.

Mendeleev left gaps in the table.

Give one reason why he needed to leave gaps.

The properties of an element depend on the arrangement of electrons in its atoms.

Lithium and fluorine have different arrangements of electrons, and different properties.

Fig. 1.2 shows the electron arrangement of fluorine.

Complete the table about the properties of lithium and fluorine.

Ideas about the structure of the atom have developed over time.

Draw lines to connect each scientist with their idea about the structure of the atom.

Give one reason why scientists needed to develop new ideas about the structure of the atom over time.

Scientists now know that the atom contains electrons, protons and neutrons.

Complete the table by giving the charge of each of these particles.

Electrons are arranged in shells around the outside of the atom.

Give the location of the other particles in the atom.

How many electrons, protons and neutrons are there in an atom of phosphorus?

Use the Data Sheet.

Electrons........

Protons........

Sodium is in Group 1 of the Periodic Table.

Complete the diagram to show the arrangement of electrons in a sodium atom. Use the Data Sheet.

Crude oil is a mixture of hydrocarbons.

How is crude oil separated into fractions?

Cracking Crystallisation Filtration Fractional distillation Titration

The fractions in crude oil are needed for fuels and other uses.

Some fractions are needed in larger amounts than other fractions.

The table gives information about the percentage of each fraction in crude oil and the percentage of each fraction needed. It also shows the number of carbon atoms in each fraction.

Name two fractions where the percentage of fraction needed is greater than the percentage in crude oil.

Which three fractions in the table contain C₁₀H₂₂?

Diesel Fuel oil Gas Naphtha Paraffin Petrol

A process is used to break down larger molecules into smaller molecules.

What is the name of this process?

Cracking Crystallisation Filtration Fractional distillation Titration

The process in (b)(iii) is used to break down naphtha to make petrol.

Give two reasons why naphtha is broken down to make petrol.

Use data from the table to support your answer.

A molecule with ten carbon atoms can be broken down into a molecule with eight carbon atoms and one other molecule.

Complete the symbol equation to show the formula of the other molecule formed.

The diagrams show 3D models of the structures of five hydrocarbons in crude oil.

Which two structures have the formula C₈H₁₈?

Tick (✓) two boxes.

Which structure is an alkene?

Give one reason for your answer.

Crude oil is a finite source of hydrocarbons.

Define finite.

The table shows some information about diamond, sodium chloride and methane.

Complete the table.

Structures can also be shown by dot and cross diagrams.

Complete the dot and cross diagram for methane.

Show outer electrons only, and label each atom.

Which features of a methane molecule are shown by a 3D structure and a dot and cross structure?

Tick (✓) one box in each row.

Why does diamond have a much higher boiling point than methane?

Tick (✓) two boxes.

Sarah does an experiment. She adds small pieces of zinc to 50 cm³ of 0.1 mol / dm³ sulfuric acid.

She measures the volume of hydrogen gas collected every 30 seconds.

Sarah finds that the reaction is very slow.

Describe two ways in which Sarah could change her experiment to make the rate of reaction faster.

Sarah plots a graph from her results, as shown in Fig. 6.2.

What happens to the rate of the reaction during the first 4 minutes?

Tick (✓) one box.

What is the total volume of hydrogen collected after 4.5 minutes?

Why does the graph level out after 4.5 minutes?

Plot the results in the table on Fig. 6.2 and draw a line of best fit.

Magnesium and sodium are reactive metals.

Magnesium reacts very slowly with cold water.

Write the balanced symbol equation for this reaction.

How does the equation show that magnesium is oxidised in this reaction?

Sodium reacts quickly with cold water to form hydrogen gas and sodium hydroxide solution.

Sodium hydroxide solution is an alkali.

What tests can be used to show that an alkali and hydrogen gas are formed?

Draw lines to connect each product with its correct test.

Why does sodium react more quickly with cold water than magnesium?

Magnesium and sodium are extracted from their compounds by electrolysis.

Electrolysis does not work if ionic solids are used. The ionic solids must be melted before electrolysis.

Explain why solid ionic compounds must be melted before electrolysis.

Give the name of the product formed at each electrode when molten sodium chloride is electrolysed.

Positive electrode........

Negative electrode........

A medicine company makes tablets which contain magnesium hydroxide.

Jamal uses dilute hydrochloric acid in a titration to check the mass of magnesium hydroxide in one tablet.

Magnesium hydroxide reacts with dilute hydrochloric acid to form a salt and water.

Complete the word equation for the reaction.

........

Jamal adds water and indicator to one tablet in a conical flask. He then adds the acid to the conical flask from a burette until all of the magnesium hydroxide has reacted.

He uses the burette to find the volume of acid that reacts with the magnesium hydroxide in the tablet.

Describe two things that he needs to do to get an accurate value for this volume.

Jamal uses his results to work out the mass of magnesium hydroxide in one tablet.

Calculate the relative formula mass of magnesium hydroxide, Mg(OH)₂.

Use the Data Sheet.

The tablets are sold in packs of 100 tablets.

Jamal tests five tablets from three packs of tablets, Pack A, Pack B and Pack C.

Table 8.1 shows his results.

Each tablet should contain a mass of 600 mg of magnesium hydroxide.

The required standard is that each tablet must be within 10 mg of this mass.

Complete Table 8.2 by deciding if each pack meets the required standard.

Tick (✓) one box in each row.

Tablets are an example of a type of substance called a formulation.

Complete the sentences to describe a formulation.

A formulation is a mixture / single substance.

Its composition is fixed / variable.

Which method can be used to show if a substance is pure or impure?

Tick (✓) one box.

The table shows data about the composition of the Earth’s atmosphere 4 billion years ago and

Complete the table to show the approximate percentage of other gases in the atmosphere

4 billion years ago.

Four billion years ago the Earth was extremely hot.

When the temperature of the Earth cooled to below 100 °C there was a large decrease in the amount of water vapour in the atmosphere.

Describe what happens when hot water vapour cools to below 100 °C.

Use ideas about arrangement and speed of particles in your answer.

How and why have the percentages of carbon dioxide and oxygen in the atmosphere changed over time?

Use data from the table to support your answer.

Some rocks are red because they contain iron oxide.

Iron oxide was formed when iron in the rocks reacted with oxygen in the atmosphere.

Complete the balanced symbol equation for the reaction which produces iron oxide.

Scientists think these red rocks formed 2.3 million years ago.

Suggest why these rocks could not form 4 billion years ago.

Use data from the table to support your answer.

Table 10.1 shows data about the sizes of some particles.

James comments on the data in Table 10.1.

Discuss James’ comment.

Use Table 10.1 to support your answer.

Table 10.2 shows information about the particles in some silver powders.

Which type of powder in Table 10.2 provides the biggest surface area for a given volume of silver?

Give one reason for your answer.

James thinks that the data in Table 10.2 gives this relationship.

Is James correct?

Explain your answer.

The different ways that nanoparticles are used depends on their properties.

Draw lines to connect each property of nanoparticles with the use that depends on it.

Nanoparticles are used as catalysts.

Which two statements explain how a catalyst increases the rate of a reaction?

Tick (✓) two boxes.