OCR GCSE Combined Science B (21st Century) Paper 2 June 2018 question paper

Mendeleev developed the first Periodic Table. He looked for patterns in the properties of elements.

He discovered that by putting the elements in order of their atomic mass he could group together elements with similar properties.

The properties of some of the elements did not fit into the pattern.

What did Mendeleev do to make the pattern of properties fit?

Tick (✓) two boxes.

The modern Periodic Table puts elements in order of their atomic number.

Table 1.1 shows some information about fluorine and sodium.

Use the Periodic Table to help you to complete the missing information in Table 1.1.

Water is found naturally in very large amounts on Earth.

Table 2.1 shows some changes that produce water.

Place a tick (✓) in one box in each row to show whether each change is a physical change or chemical change.

The different states of water can be explained by the particle model.

Complete Table 2.2 to describe the particles in the three states of water.

Some have been done for you.

Methane and ammonia are compounds also found naturally on Earth.

Table 2.3 shows the boiling point of water, methane and ammonia.

Use ideas about forces between particles to explain why the compounds in Table 2.3 have different boiling points.

Crude oil was formed from plants and animals which lived millions of years ago.

Crude oil contains a mixture of compounds called alkanes.

Alkanes contain only carbon and hydrogen atoms.

What name is given to compounds that contain only carbon and hydrogen atoms?

Acids Crystals Hydrocarbons Salts Starch

The table gives information about some alkanes.

Describe how the formulae of the compounds change as the molecules of alkanes get larger.

Which compound is a liquid at 20 °C? Use the data in the table to explain your answer.

What are the general trends in melting points and boiling points of alkanes as the molecules get larger?

Which alkane does not fit the general trend in melting and boiling points?

Explain your reasoning.

All alkanes have the general formula C_nH_2n+2.

What is the formula for the alkane that has 8 carbon atoms?

Chemists use a range of different separating techniques to separate mixtures.

Which method is used to separate the alkanes in crude oil?

Chromatography Crystallisation Dissolving Filtration Fractional distillation

The diagrams show the arrangement of electrons in a carbon atom and a hydrogen atom.

A methane molecule contains an atom of carbon joined to 4 atoms of hydrogen.

Complete the diagram to show the arrangement of electrons in a molecule of methane.

Jack works for a company that makes chemicals for farming. One of the chemicals is copper sulfate.

Jack is looking at ways to make copper sulfate.

Jack adds copper metal to dilute sulfuric acid. There is no reaction.

Which statement explains why?

Tick (✓) one box.

Jack finds out that copper oxide also reacts with dilute sulfuric acid to make copper sulfate.

He adds solid copper oxide to dilute sulfuric acid until no more solid reacts.

At the end of the experiment, Jack has a beaker of dilute copper sulfate solution with some unreacted solid copper oxide.

Which method should Jack use to separate the dilute copper sulfate solution from the solid copper oxide?

Condensation Crystallisation Distillation Evaporation Filtration

Jack makes some crystals from the dilute copper sulfate.

He starts by setting up this apparatus.

Describe how Jack can use this apparatus to make crystals.

Jack measures the mass of the copper oxide at the start of the experiment. He measures the mass of the copper sulfate crystals at the end of the experiment.

The table shows his results.

Calculate the mass of copper oxide Jack needs to use to make 5 kg of copper sulfate crystals. Give your answer in kg.

Diamond and graphite both consist of carbon atoms bonded together.

Their structures are shown below:

The table contains some statements about diamond and graphite.

Place one tick (✓) in a box for each statement to show whether it is true for diamond only true for graphite only or true for both diamond and graphite.

Graphite is used in pencils.

Use ideas from the structures to explain why graphite can make marks on paper.

Tick (✓) two boxes next to the best explanations.

Indigestion may be caused by excess acid. Jane investigates indigestion tablets.

The active compound in each tablet is calcium carbonate which reacts with excess acid. Each tablet also contains other ingredients.

The tablets are a formulation and not a pure substance.

Put ticks (✓) in one box in each row to show which statements about formulations and pure substances are true and which are false.

The acid in the stomach is mainly hydrochloric acid.

Jane adds some indigestion tablets to some hydrochloric acid in a beaker.

Jane sees bubbles of carbon dioxide form when she adds the tablets to the acid.

Describe one other observation that Jane would see.

Jane tests the carbon dioxide that is made.

What is the correct test for carbon dioxide?

Tick (✓) one box.

Jane adds five indigestion tablets to some acid in a beaker.

When the tablets react with the acid, the mass decreases because carbon dioxide gas leaves the beaker.

Jane uses a balance to work out the mass change during the reaction.

These are her results:

Mass of 5 tablets = 7.55 g Mass of beaker with acid before adding tablets = 200.49 g Mass of beaker and contents at the end of reaction = 206.24 g

Jane adds the five tablets to the beaker of acid.

Calculate the total mass of the beaker and all of its contents at the start of the reaction.

The mass of the beaker and its contents decreases during the experiment because carbon dioxide is made.

Calculate the mass of carbon dioxide made in Jane’s experiment.

Jane finds that the reaction takes a long time.

Give two changes she could make to her experiment to make the reaction faster.

The tablets contain calcium carbonate with other ingredients.

Jane looks at a graph which shows the mass of carbon dioxide that is made when different masses of calcium carbonate react with acid.

The label on the tablets says that each tablet contains 0.5 g of calcium carbonate.

Calculate the mass of calcium carbonate in 5 tablets.

Use the graph to predict how much carbon dioxide is made from five tablets. Show how you used the graph to find your answer.

Jamal does a titration to find the concentration of some acid. He measures the volume of acid needed to react with 25.0 cm³ of alkali.

What type of reaction happens when the acid reacts with the alkali?

Crystallisation Neutralisation Oxidation Precipitation

Here are some pieces of apparatus that are used to measure out volumes of liquids.

Which is the best apparatus to use to measure out exactly 25.0 cm³ of alkali into a conical (i) flask?

Burette Graduated beaker Measuring cylinder Pipette

Which is the best apparatus to use to accurately measure out the amount of acid needed to react with the alkali?

Burette Graduated beaker Measuring cylinder Pipette

Jamal does a rough trial before he does his repeat titrations.

Explain how he uses the result of his rough trial to help him to do his repeat titrations.

Jamal ignores his rough trial when he processes his results.

What is the range of the results of Jamal’s repeat titrations ?

Identify the outlier in the results of Jamal’s repeat titrations.

Explain your choice.

Use the repeat titration results to calculate the mean value for the volume of acid added.

Give your answer to 3 significant figures.

The elements in Group 7 (Group 17) of the Periodic Table are called the halogens.

Each element has a different state and colour at room temperature.

Draw lines to connect each element with its correct state and colour at room temperature.

State Element Colour

Table 9.1 shows what happens when some halogens react with hydrogen.

Describe the trend in reactivity of the Group 7 elements with hydrogen.

A mixture of chlorine and hydrogen explodes when a small spark is added.

Does this fit the trend of the reactivity of the other Group 7 elements with hydrogen?

Explain your reasoning.

The halogens also react with reactive metals.

Potassium reacts with bromine to form potassium bromide.

Balance the symbol equation for this reaction.

Other metals also react with bromine to form metal bromides.

The formula of the metal bromide depends on the number of electrons in the outer shell of an atom of the metal.

Complete Table 9.2 which shows the products formed when different metals react with

Most cars are fitted with catalytic converters.

Harmful gases from the car engine react together in the converter to form less harmful gases.

The catalyst in the converter increases the rate of the reactions between the gases.

Use ideas about energy to explain how catalysts increase the rate of a reaction.

Catalysts are now made from nanoparticles. A nanoparticle in a catalyst is shown in the

Calculate the surface area to volume ratio of the nanoparticle. Assume that it is a cube with sides of 10 nm.