OCR GCSE Combined Science B (21st Century) Paper 4 June 2019 question paper

The element mercury is a metal. It is a liquid at room temperature and pressure.

Fig. 1.1 shows a coin floating on mercury.

Which diagram shows the arrangement of particles in liquid mercury?

Tick (✓) one box.

The coin floats because it is less dense than the mercury.

Which is the correct equation for calculating density?

Tick (✓) one box.

One use of gene technology is genetic engineering.

Scientists have taken the gene for the blue pigment (pigments are coloured chemicals) in blackberries and transferred it into tomatoes. Tomatoes with this gene are blue in colour.

Genes are short sections of a long molecule.

What is the name of this long molecule?

The blue pigment in the genetically modified tomatoes is an antioxidant.

Antioxidants prevent cell damage. This means eating blue tomatoes may be beneficial to our health. Blue tomatoes are still being tested and are not yet available for sale.

Some students are talking about blue tomatoes.

Which student talks about a risk of genetic engineering?

Which student talks about an ethical objection to genetic engineering?

Which student talks about a benefit of genetic engineering?

Here is the chromatogram of their results.

Calculate the Rf value of the red pigment in the red tomato extract, using Fig. 2.1.

Explain why the line at the bottom of the chromatogram was drawn in pencil.

Give two conclusions that the students can make from these results.

Conclusion 1

Conclusion 2

There are a number of hazards in this experiment.

Draw lines to connect each hazard to the safety procedure that should be followed.

Which two statements are needed to collect valid results?

Tick (✓) two boxes.

Nina and Kareem collected data for five sunscreens (sun creams) with different SPFs.

They also recorded the UV intensity when no sunscreen was applied to the plastic sheet.

Explain why they recorded the UV intensity when no sunscreen was applied to the plastic sheet.

Table 3.1 shows the data that they collected for sunscreen with an SPF of 20.

Calculate the mean UV intensity from the data in Table 3.1.

Give your answer to 2 significant figures.

Mean UV intensity =........ mW / cm²

Nina and Kareem wanted to check whether their measurements were accurate.

Which statement explains how they did this?

Tick (✓) one box.

Table 3.2 shows the mean UV intensities of Nina and Kareem’s other results.

Complete the graph by plotting the results in Table 3.2, and drawing a line of best fit.

Add labels to the axes showing the units.

Write down two conclusions Nina and Kareem can make from the graph.

Explain why it is important to use sunscreen (sun cream) when your skin is exposed to UV radiation.

Our core body temperature needs to be kept at about 37 °C.

Maintaining body temperature relies on our nervous system.

Explain why our body temperature needs to be maintained around 37 °C.

Low temperatures can be dangerous for humans.

Complete the sentences to describe why humans wear jackets in cold weather.

Use words from the list. You may use each word once, more than once or not at all.

conductors low reflected generators

insulators lost high conserved

Humans can survive in freezing temperatures with the correct clothing.

Jackets filled with feathers are good........

This is because feathers have a........ thermal conductivity.

They reduce the amount of heat........ by the body.

Temperature regulation is an example of homeostasis.

Which other processes in humans are maintained by homeostasis?

Tick (✓) two boxes.

HIV is an infection caused by a virus. People with this virus are HIV+. HIV weakens the immune system.

Tuberculosis (TB) is a disease caused by bacteria. It may be fatal in people with a weak immune system.

Fig. 5.1 shows the number of cases of TB and HIV per 100,000 people in the Central African Republic in one year.

Calculate the percentage of people in the Central African Republic who have tuberculosis and who are also HIV+.

Give your answer to 1 decimal place.

Six other African countries were investigated by scientists. The results are shown in Fig. 5.2

Percentage of TB cases that are also HIV+ (%)

Fig. 5.2

Which statements about the graph are true and which are false ?

Tick one box in each row.

What is the correct definition of a positive correlation ?

Tick (✓) one box.

Oil tankers transport crude oil. Crude oil is a mixture of hydrocarbons.

Occasionally they may be involved in an accident and catch fire as shown.

Explain why the burning hydrocarbons in the oil produce thick black smoke.

The hydrocarbon fractions in crude oil are separated by fractional distillation.

Complete the sentences about fractional distillation.

Use words from the list. Each word can be used once, more than once, or not at all.

dissolved cooled crystallise

evaporate heated melt

During fractional distillation the mixture is heated and the fractions........

at different temperatures.

The separated fractions are then........ so that they condense.

The hydrocarbons in crude oil are mostly alkanes.

Octane is an alkane. Its molecular formula is C₈H₁₈.

Determine the empirical formula of octane.

Some ships carry condensate oil, rather than crude oil.

Give two similarities and two differences between crude oil and condensate oil.

Use Fig. 6.1 to support your answers.

Similarity 1

Similarity 2

Difference 1

Difference 2

The table shows some other differences between crude oil and condensate oil.

Which statement best explains why there is a range of temperatures for the boiling point of crude oil and condensate oil?

Tick (✓) one box.

Some people conclude that condensate oil is more dangerous to carry than crude oil.

Evaluate this conclusion.

Use the data in the table to support your answer.