AQA GCSE Synergy Paper 3: Physical sciences Higher November 2020 question paper 8465/3H

A student investigated how the power output of a filament lamp varied with the current in the lamp.

Figure 1 shows part of the circuit the student used.

To calculate power output the student measured the current in the lamp and the potential difference across the lamp.

Complete Figure 1 by adding an ammeter and a voltmeter to make the measurements.

Use the correct circuit symbols.

Which energy store in the battery decreases when the lamp is switched on?

What happens to the energy transferred by the lamp?

Figure 2 shows the results.

Describe how varying the current affects the power output of the filament lamp.

Write down the equation which links current (I), power (P) and resistance (R).

Determine the resistance of the lamp when the current in the lamp is 0.22 A

A student investigated the temperature increase when magnesium powder was added to copper sulfate solution.

Figure 3 shows the apparatus used.

This is the method used.

1. Add copper sulfate solution to a beaker.

2. Measure the initial temperature of the copper sulfate solution.

3. Add 0.1 g of magnesium powder.

4. Stir the mixture.

5. Measure the maximum temperature of the mixture.

6. Repeat steps 1 to 5 with different masses of magnesium powder.

Give two control variables the student should use.

Suggest one change to improve the accuracy of the investigation.

Table 1 shows the student’s results.

Explain the conclusions that can be made from the trends shown in the results.

Use data from Table 1 in your answer.

This question is about iron and steel.

Figure 4 shows a flow chart for the production of iron and steel from iron ore.

Iron ore consists mainly of iron oxide.

In the blast furnace iron oxide reacts with carbon monoxide to form iron and carbon dioxide.

Complete the equation for the reaction between iron oxide and carbon monoxide.

You should balance the equation.

Iron oxide is reduced in the reaction with carbon monoxide.

What does ‘reduced’ mean in this reaction?

Cast iron is an alloy.

Cast iron contains carbon.

Figure 5 shows the arrangement of atoms in pure iron and in cast iron.

Explain why cast iron is harder than pure iron.

In addition to cast iron, scrap steel is added to the steel-making furnace.

Give three environmental advantages of recycling scrap steel in this way.

This question is about the enzyme amylase.

Amylase can only digest starch.

Explain why amylase cannot digest other substances.

Students investigated the effect of pH on the rate of starch digestion.

This is the method used.

1. Add 2 cm³ of amylase solution at pH 5.0 to a test tube in a water bath at 37 °C

2. Add 2 cm³ of starch suspension to the same test tube.

3. Start the timer.

4. Remove a drop of the amylase-starch mixture after 30 seconds.

5. Test the drop for starch.

6. Repeat steps 4 to 5 until no starch is detected.

7. Record the total time taken for no starch to be detected.

8. Repeat steps 1 to 7 using amylase solution at different pHs.

Which is the dependent variable in the investigation?

Tick (✓) one box.

Describe the test for starch.

Give the result of the test if starch is present.

The amylase solution and starch suspension were kept in the water bath at 37 °C for 10 minutes before being mixed.

Why were the amylase and starch kept at 37 °C for 10 minutes before being mixed?

Table 2 shows the results.

Student A concluded that:

‘The optimum pH for amylase is 7.5’.

Give one reason why this conclusion could be correct.

Use Table 2.

Student B concluded that:

‘The optimum pH is between 7.0 and 8.0 but may not be 7.5’.

How can student B determine a more accurate value for the optimum pH?

Use Table 2.

This question is about the hydrocarbons obtained from crude oil.

Octane is a hydrocarbon.

How does the formula of octane show that octane is an alkane?

The fractions in crude oil are separated by fractional distillation.

Figure 6 shows a fractionating column.

Table 3 gives some properties of different fractions separated from crude oil.

Which fraction in Table 3 is the most viscous?

Give one reason for your answer.

Tick (✓) one box.

Describe how the fraction containing octane is separated from crude oil.

Use data from Table 3 in your answer.

Some security lights automatically switch on when it gets dark.

Figure 7 shows a security light.

Figure 8 shows part of a circuit that can be used to switch the security light on and off.

The circuit symbol for the LDR in Figure 8 is not correct.

Which is the correct circuit symbol for the LDR?

Tick (✓) one box.

The security light turns on when the potential difference across the LDR is 2.0 V

Determine the resistance of the LDR when the potential difference across the LDR is 2.0 V

Use Figure 8.

A charge of 3.24 C flows through the LDR in 40.0 minutes.

Calculate the current in the LDR.

Sometimes dirt can cover the LDR on the security light.

What effect would dirt on the LDR have on the security light?

Tick (✓) one box.

Figure 9 shows a car travelling at a constant speed on a straight, level road.

Figure 10 shows a free body diagram for the car.

Explain how the free body diagram shows that the resultant force on the car is zero.

Table 4 shows how the braking distance of a car varies with the speed of the car.

A car decelerates from 24 m/s to 0 m/s

The work done by the brakes in decelerating the car is 210 000 J

Determine the mean braking force.

Use information from Table 4.

Give your answer to 2 significant figures.

The braking distance is directly proportional to the kinetic energy of the car.

Explain how the data in Table 4 supports this relationship.

This question is about halogens.

Bromine reacts with sodium to produce sodium bromide.

Describe the structure of and bonding in sodium bromide.

The equation for the reaction is:

1 g of bromine reacts with sodium.

Calculate the number of bromine molecules in 1 g of bromine.

1 mole of bromine contains 6.02 × 10²³ bromine molecules.

Relative formula mass (M_r) of bromine = 160

Table 5 shows the boiling points of some halogens.

Explain the trend in the boiling points of the halogens.

This question is about the industrial process used to produce ammonia.

Ammonia is produced from nitrogen and hydrogen.

Complete the dot and cross diagram for the ammonia molecule shown in Figure 11.

Show only the electrons in the outer shell of each atom.

Hydrogen is obtained from natural gas.

One stage in the process is to react carbon monoxide with steam.

The equation for the reaction is:

The forward reaction is exothermic.

In the industrial process, the reaction occurs at approximately 400 °C

The reaction between carbon monoxide and steam reaches dynamic equilibrium.

Which statement describes dynamic equilibrium?

Tick (✓) one box.

The reaction between carbon monoxide and steam is faster at 600 °C than at 400 °C

Explain why a temperature of 600 °C is not used in the industrial process.

Predict the effect of increasing the pressure on the yield of hydrogen.

Give one reason for your answer.

Give two reasons why a catalyst is used in the reaction between carbon monoxide and steam.

The carbon dioxide produced in this reaction can be used in fizzy drinks.

In fizzy drinks carbon dioxide gas dissolves in water to form an aqueous solution of carbonic acid.

Carbonic acid is a weak acid.

Explain the difference between a weak acid and a strong acid.

The equation for the production of ammonia from nitrogen and hydrogen is:

1.275 × 10¹¹ kg of ammonia is used each year to manufacture fertilisers.

This is 85% of the ammonia produced each year.

Calculate the mass of nitrogen needed to manufacture the total mass of ammonia produced each year.

Relative atomic masses (A_r): H = 1 N = 14

Figure 12 shows the equipment a student used to investigate the motor effect.

Explain why the wire moves when the switch is closed.

The student recorded these measurements:

• potential difference across wire = 1.50 V

• resistance of wire = 0.60 Ω

• length of wire in magnetic field = 0.050 m

• force on wire = 3.75 × 10⁻⁴ N

Calculate the magnetic flux density of the magnetic field.

Give the unit.