OCR GCSE Combined Science B (21st Century) Paper 4 November 2020 question paper

Sarah draws three different cells, cell A, cell B, and cell C, as shown in Fig. 1.1.

What type of cell is cell A ?

What is found in all three cells?

Tick (✓) one box.

Cell C has a length of 0.0047 mm.

1 mm = 1000 m.

Calculate the length of cell C in micrometres, m.

Length =........ m

Microscopes can be used to look at cells.

Complete the sentences about microscopes.

Use words from the list.

You can use each word once, more than once, or not at all.

focus light resolution neutron

magnify depth electron power

A microscope can be used to........ parts of a cell that cannot be seen with

the naked eye.

........ microscopes have a higher magnification and........

than........ microscopes, so they can be used to look at parts of a cell in

more detail.

Sarah uses the microscope in Fig. 1.2 to look at some cells.

The steps Sarah takes to look at some cells are listed below but are not in the correct order.

A Place the prepared slide on the microscope stage.

B Turn the focus wheel to make the image clear.

C Change the objective lens to a higher magnification.

D Prepare a microscope slide of the cells.

E Use the objective lens with the lowest magnification.

Write the letters in the boxes to show the correct order.

The first one has been done for you.

Which combination of eyepiece and objective lens will produce a magnification of × 400?

Tick (✓) one box.

Eyepiece
Objective lens

Ben says the value for repeat 5 is an outlier.

Give one reason why Ben says this.

Suggest what has caused the outlier.

Calculate the mean rate of water uptake by the plant in Ben’s experiment.

Use data from the table.

Mean rate of water uptake =........ mm³ / min

Ben wants to investigate the different factors that speed up the rate of water uptake by the plant.

Suggest three ways he can change his experiment to speed up the rate of water uptake.

Suggestion 1

Suggestion 2

Suggestion 3

Table 3.1 shows the properties of some materials.

Which material in Table 3.1 should be used as an insulator around electrical wires found in a plug, as shown in Fig. 3.1?

aluminium LDPE steel

Overhead electrical cables used in the National Grid need to be flexible, and as light as possible.

Which material in Table 3.1 should be used for overhead electrical cables in the National Grid as shown in Fig. 3.2 ?

aluminium LDPE steel

Which statements about the materials in Table 3.1 are true and which are false ?

Tick (✓) one box in each row.

Suggest which material costs the least to recycle.

Use data from Table 3.1 to explain your answer.

* In some professional cycling sports, competitors have to run with their bicycles.

Table 3.2 shows some materials used to make professional cycling bicycles.

Give the advantages and disadvantages of using carbon fibre for professional cycling bicycles.

Use the information in Table 3.2 and calculations to support your answer.

Some students are talking about the movement of molecules in plant cells.

Which student is correctly talking about osmosis?

Tick (✓) one box.

Which student is correctly talking about active transport?

Tick (✓) one box.

Mia is investigating osmosis in potato cells. She writes a six-step plan.

Step 1. Cut 5 pieces of potato.

Step 2. Weigh them and record the masses.

Step 3. Put them into different salt solutions.

Step 4. Leave them for a few minutes.

Step 5. Take them out and weigh them again.

Step 6. Calculate the percentage change in mass.

Suggest how Mia can improve Steps 1, 3 and 4 of her plan to ensure her investigation is valid.

Step 1........

Step 3........

Step 4........

Mia’s measurements for one piece of potato are shown in the table.

Calculate the percentage decrease in mass for this piece of potato. Use the equation: percentage decrease = × 100 Give your answer to 3 significant figures.

Beth is investigating how changing the length of a wire affects its resistance.

Beth calculates the resistance of different lengths of the section of track, and her results are shown in the table.

What can be concluded from Beth’s results?

Use the data in the table to support your answer.

Calculate the current in the circuit when there is a potential difference of 3.0 V across 50 cm of track.

Use the equation: potential difference = current × resistance

Beth makes three changes to the investigation to improve it.

Draw lines to connect each change in the investigation with its correct improvement.

The diagram shows part of a rollercoaster ride.

Complete the sentences about the energy transfers in a rollercoaster ride.

Use words from the list.

You can use each word once, more than once or not at all.

sound kinetic electrical

gravitational potential
thermal
increases

decreases
speed
distance travelled

As work is done by an electric motor to move the train to the top of the rollercoaster

ride, the........ energy store of the train increases. As the

train starts moving down, this energy store........ The

........ of the train increases as the train starts moving down, which

causes the........ energy store of the train to increase. Some energy

is dissipated into the inaccessible thermal energy store of the surroundings.

Which equation should be used to calculate gravitational potential energy?

Tick (✓) one box.

At the highest point of the rollercoaster ride, the train is 40 m from the ground.

The train has a mass of 1400 kg when it is full of passengers.

Calculate the gravitational potential energy stored in the train when it is at the highest point of the rollercoaster ride.

Gravitational field strength = 10 N / kg

The train reaches a maximum speed of 90 km / h.

Calculate the maximum kinetic energy of the train when it is full of passengers.

Use the equation: kinetic energy = 0.5 × mass × speed²

The electric motor that provides the energy to lift the train to the top of the rollercoaster ride has an efficiency of 0.40.

An empty train has 360 000 J of gravitational potential energy at the highest point of the rollercoaster ride.

Calculate the total energy transferred by the electric motor.

Use the equation: efficiency = useful energy transferred ÷ total energy transferred

Give your answer in kJ.

Complete the sentences about the greenhouse effect.

Use words from the list.

You can use each word once, more than once or not at all.

absorbed microwave reflected methane

ultraviolet scattered nitrogen infrared

The Earth receives electromagnetic radiation from the Sun. Some of this radiation

is........ by the Earth’s surface, causing it to warm up.

........ radiation is then emitted from the Earth’s surface. Some of

this radiation is then........ by greenhouse gases in the atmosphere

such as carbon dioxide and........, which is then re-emitted in all

directions.

Carbon dioxide is a greenhouse gas.

Fig. 7.1 shows the mass of carbon released worldwide every year from 1900 to 2014.

Describe the trend shown in Fig. 7.1 and suggest two possible explanations for this trend.

Trend........

Explanation 1........

Explanation 2........

Give one reason why the data in Fig. 7.1 may be inaccurate.

Describe two effects of the trend seen in Fig. 7.1.

Effect 1........

Effect 2........

Carbon capture and storage is a process where carbon dioxide is collected and stored underground.

Suggest two negative effects of carbon capture and storage on the environment.

Coal and oil are non-renewable sources of energy.

Biofuels such as wood or straw pellets are renewable sources of energy.

How are non-renewable sources of energy different from renewable sources of energy?

Biofuels are carbon neutral. This means that their use does not increase carbon dioxide levels in the atmosphere. Coal is not carbon neutral.

Which two statements explain why biofuels are carbon neutral?

Tick (✓) two boxes.