AQA GCSE Synergy Paper 3: Physical sciences Higher June 2019 question paper 8465/3H

Catalase is an enzyme.

What type of molecule is an enzyme?

Hydrogen peroxide decomposes in the presence of catalase.

This is the equation for the reaction:

Describe how the student could test for the gas produced.

A student investigated the effect of pH on the activity of catalase.

Describe how the student could use an indicator to measure the pH of a solution.

Table 1 shows the results.

What is the optimum pH for catalase in this reaction?

Use Table 1.

How could the student find a more accurate value for the optimum pH?

Tick (✓) one box.

Explain the result for catalase at pH 3.0

A student investigated magnets.

The student used a paper clip, metre rule and magnets.

Figure 1 shows the apparatus with one magnet.

Write down the resolution of the metre rule.

Explain why the paper clip is attracted to the magnet.

The student placed the paper clip at different distances from the magnet.

She recorded the minimum distance at which the paper clip did not move towards the magnet.

She repeated the investigation using different numbers of magnets.

Suggest why the magnets used should be identical.

Table 2 shows the results of the investigation.

Predict the value X in Table 2.

There is a resultant force on the paper clip. The resultant force causes the paper clip to accelerate towards the magnet.

Write the equation which links acceleration, mass and resultant force.

The mass of the paper clip is 0.0012 kg

Calculate the acceleration of the paper clip when the resultant force on it is 0.000168 N

Give the unit.

The Earth has a magnetic field.

The magnetic field is probably caused by movements inside the Earth.

Name the part of the Earth in which the movements take place.

Give one piece of evidence to show that the Earth’s magnetic field has changed over time.

This question is about graphene and graphite.

Graphene is a single layer of graphite.

Figure 2 represents part of the structure of graphene.

Figure 2

Graphene is one atom thick. The diameter of the atom is 3.4 × 10^–10 m

What is the thickness of a graphene layer in nanometres?

1 nm = 10^–9 m

Tick (✓) one box.

Which is one use of graphene?

Tick (✓) one box.

Graphene and graphite are used in electronics.

Suggest one reason why graphene is a more suitable material for use in electronics than graphite.

Figure 3 represents part of the structure of graphite.

Graphite is used as a contact in electric motors because graphite:

• conducts electricity

• is slippery.

Explain why graphite has these properties.

You should refer to the structure and bonding of graphite in your answer.

This question is about hydrocarbons.

When a hydrocarbon C₁₀H₂₂ is cracked, two substances are produced.

Complete the equation for the reaction.

Explain why the hydrocarbon C₇H₁₆ has a lower boiling point than C₁₀H₂₂

Ethanol is produced by reacting ethene with steam.

The equation for the reaction is:

Figure 4 shows the percentage yield of ethanol using different reaction conditions.

Explain why changing the pressure affects the percentage yield of ethanol.

The forward reaction is exothermic.

How does Figure 4 provide evidence for this?

Figure 5 shows part of a reaction profile diagram.

A catalyst is used in the reaction to produce ethanol.

Complete Figure 5 to show how the catalyst increases the rate of this reaction.

You should label the reaction profile diagram.

Suggest why the catalyst does not affect the yield of ethanol at equilibrium.

A student investigated how the resistance of a thermistor varies with temperature.

The student made measurements to determine the resistance of the thermistor at room temperature. He used an ammeter and a voltmeter.

Complete the circuit diagram to show a circuit the student could use.

The student repeated the measurements with the thermistor at different temperatures.

He plotted a graph of resistance against temperature.

Figure 6 shows the graph.

One set of readings was:

• potential difference = 5.60 V

• current = 0.04 A

Determine the temperature of the thermistor.

Explain how the graph shows that the thermistor is most sensitive to changes in temperature between 20 °C and 25 °C

A student investigated the rate of the reaction between magnesium and hydrochloric acid.

The student measured the volume of hydrogen gas produced.

How could the student collect and measure the volume of gas produced?

At the start of the investigation the volume of gas was 0 cm³

The student took readings at 20-second intervals.

Readings for the volume of gas were 24 cm³, 44 cm³, 59 cm³, 70 cm³, 76 cm³ and 79 cm³

Draw a results table for the investigation.

Include the student’s results in the table.

The student repeated the investigation at a higher temperature.

Figure 7 shows the results.

Determine the rate of reaction at 30 seconds.

Show your working on Figure 7.

Give your answer to 2 significant figures.

The rate of reaction increases at higher temperatures.

Explain why.

Answer in terms of particles.

A 1 kg mass is made from a platinum and iridium alloy.

The platinum and iridium alloy is harder than pure platinum.

Explain why alloys are harder than the pure metal.

The 1 kilogram mass consisted of 900 g platinum and 100 g iridium.

What was the ratio of platinum atoms to iridium atoms in the alloy?

Relative atomic masses (A_r): Pt = 195
Ir = 192

Tick (✓) one box.

The Avogadro constant is the number of atoms in 1 mole of a substance.

What is the value of the Avogadro constant?

Tick (✓) one box.

Scientists could use a sample of silicon to define the Avogadro constant.

Copper is an impurity in the silicon sample.

There are 70 nanograms of copper in 1 g of the sample.

Calculate the mass of copper in grams in 1 kg of the sample.

Give your answer in standard form.

1 nanogram = 10^–9 g

Silicon mainly occurs in the Earth’s crust as silicon dioxide.

Figure 8 represents part of the structure of silicon dioxide.

Determine the empirical formula of silicon dioxide.

Use Figure 8.

Describe the structure and bonding in silicon dioxide.

A student planned to make copper sulfate crystals from excess copper oxide and dilute sulfuric acid.

The equation for the reaction is:

Why is it necessary to add excess copper oxide?

This is the method used.

1. Add 25 cm³ of dilute sulfuric acid to a conical flask.

2. Gently warm the dilute sulfuric acid.

3. Add excess copper oxide to the dilute sulfuric acid.

4. Stir the mixture.

5. Heat to evaporate all the water from the mixture.

Suggest two improvements to the method.

Explain why each improvement is needed.

The student used:

• 2 g of copper oxide (in excess)

• 25 cm³ of a solution of dilute sulfuric acid with a concentration of 49 g/dm³

Determine by how many moles the copper oxide (CuO) was in excess.

Relative atomic masses (A_r): Cu = 63.5 O = 16

Relative formula mass (M_r) of sulfuric acid = 98

A student investigated the motor effect.

Figure 9 shows the apparatus used.

The student closed the switch and the wire moved.

Explain why.

Give two ways of reversing the direction of the movement of the wire.

Electric motors use the motor effect.

Energy is supplied to the electric motor by a battery.

The battery is charged using a charger.

When the charger is connected to the battery, the potential difference across the battery is 15.0 V

The total energy stored when the battery is fully charged is 0.81 MJ

The average current used to charge the battery is 3.00 A

Calculate the time taken to fully charge the battery.

The charger is plugged into the mains electricity supply.

This is an alternating supply.

Give two other properties of the UK mains electricity supply.