OCR GCSE Combined Science B (21st Century) Paper 2 November 2020 question paper

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Atoms contain protons, neutrons and electrons.

(a)(i)

Complete the table to give information about protons, neutrons and electrons.

	Relative mass	Relative Charge	Location in the atom
Proton	1	+1	............................
Neutron	............................	............................	............................
Electron	............................	............................	in shells

[3]

Answer

(a)(ii)

The Periodic Table shows information about atoms of sulfur.

What is the group number and period number for sulfur?

Use the Data Sheet.

[2]

Answer

(b)

The diameter of an atom is approximately 0.1 nm.

The diameter of a bacterium is approximately 10 000 times bigger than the diameter of an atom.

Estimate the diameter of a bacterium, in mm.

1 mm = 1 000 000 nm

[2]

Answer

The demand for drinking water in the world is increasing and we need new ways of supplying drinking water.

Waste water from drains and sewers can be treated, and then returned to rivers so that it can be used again.

(a)

The diagram shows the stages in the treatment of waste water.

Draw lines to connect each stage with its function.

One has been done for you.

[2]

Answer

(b)

Chlorine can also be added to water to make it safe to drink.

Describe the test and result to identify chlorine.

Test........

Result........

[2]

Answer

(c)

Typhoid is a disease which can be spread by drinking unsafe water.

Fig. 2.1 shows the number of people who had typhoid per 100 000, in a city, every 5 years, from 1890 to 1930.

Table 2.1 shows data for this city, for two years, 1890 and 1930.

(c)(i)

Complete Table 2.1.

[2]

Answer

(c)(ii)

In 1895, the number of people who had typhoid per 100 000 was 25.

Plot this data on Fig. 2.1.

[1]

Answer

(c)(iii)

Chlorine was added to the drinking water of the city after 1910.

How does the data in Fig. 2.1 show that adding chlorine to the water after 1910 made the water safer to drink?

[2]

Answer

(d)(i)

How does chlorine make the water safe to drink?

[1]

Answer

(d)(ii)

Give one benefit and one risk of adding chlorine to water.

Benefit........

Risk........

[2]

Answer

Sodium chloride is an ionic compound.

(a)

Complete the sentences about the structure and bonding of ionic compounds.

$Question 3, shown as an image$

Ions are formed when electrons / protons are shared / transferred.

The forces holding the ions together are electrostatic / magnetic.

Ions are held together in a lattice / molecule.

[3]

Answer

(b)

Fig. 3.1 and Fig. 3.2 show two ways of representing the structure and bonding of sodium chloride NaC l.

Complete the table to identify what is shown in Fig. 3.1 and Fig. 3.2.

Tick (✓) at least one box in each row.

[3]

Answer

(c)(i)

Explain why sodium chloride conducts electricity when it is molten but does not conduct electricity when it is solid.

[2]

Answer

(c)(ii)

When electricity passes through molten sodium chloride it decomposes.

Name the two products formed when molten sodium chloride decomposes.

[2]

Answer

(d)

Sodium chloride is soluble in water.

Sodium chloride crystals can be made from a solution of sodium chloride in water by the process of crystallisation.

Which two steps are needed to produce large sodium chloride crystals from a pure solution of sodium chloride?

Tick (✓) two boxes.

$Question 3, shown as an image$

[2]

Answer

(e)

Sea water contains dissolved sodium chloride. It can be used as a source of drinking water if the dissolved sodium chloride is removed.

Which two methods can be used to remove dissolved sodium chloride from sea water?

Tick (✓) two boxes.

$Question 3, shown as an image$

[2]

Answer

Cotton is a natural fibre made from plants. Polyester is a man-made, synthetic fibre made from crude oil.

(a)

Which two statements explain why plants are more sustainable raw materials than crude oil?

Tick (✓) two boxes.

$Question 4, shown as an image$

[2]

Answer

(b)

Most shirts are made from polyester or cotton fabric.

The table shows data from two parts of a life-cycle assessment, for both polyester shirts and cotton shirts.

The data is for 1000 polyester shirts and 1000 cotton shirts.

	1000 polyester shirts	1000 cotton shirts
Production of the two fabrics from raw materials
Raw material	Crude oil	From plants
Energy used to make fibres from raw materials (MJ)	97	60
Energy used to make the fabric from the fibres (MJ)	33	40
Total water used in production (dm³)	1307	25 900
Total carbon dioxide emissions during production (kg)	3.8	5.3

Disposal of the shirts (by burning)
Energy released (MJ)	33	7
Carbon dioxide emissions (kg)	5.8	5.5

(b)(i)

What should be considered when completing a life-cycle assessment for both polyester shirts and cotton shirts?

Tick (✓) two boxes.

$Question 4, shown as an image$

[2]

Answer

(b)(ii)

Calculate the difference in the total energy used for the production of the two fabrics from raw materials.

Use data from the table.

[2]

Answer

(b)(iii)

Give two advantages to the environment of making polyester fabric rather than cotton fabric.

Use data from the table to support your answers.

[2]

Answer

(b)(iv)

Give one disadvantage to the environment of making polyester fabric rather than cotton fabric.

Use data from the table to support your answer.

[1]

Answer

(c)(i)

There are many different methods of disposing of shirts at the end of their life-cycle.

The table gives some information about disposal by burning.

Suggest two other methods of disposing of shirts.

[2]

Answer

(c)(ii)

When shirts are disposed of by burning, energy is released.

Suggest one use for this energy.

[1]

Answer

(a)

When acids react with alkalis, a salt is formed.

Different salts can be made by reacting different acids and alkalis together.

(a)(i)

Draw lines to connect each salt with the acid and alkali that are used to make it.

[3]

Answer

(a)(ii)

[3]

Answer

Nina investigates the combustion of ethanol.

(a)

Complete the balanced symbol equation for the combustion of ethanol in air.

$Question 6, shown as an image$

[2]

Answer

(b)

Nina uses this apparatus for her experiment.

Nina measures the mass of the burner containing ethanol, and the temperature of the water at the start of the experiment. She also measures the mass of water in the can.

She burns some ethanol, and then measures the temperature of the water and the mass of the burner containing ethanol at the end of the experiment.

(b)(i)

What apparatus does Nina need to make her measurements?

$Question 6, shown as an image$

balance beaker condenser funnel pH meter thermometer

[2]

Answer

(b)(ii)

Nina uses a lighted splint to light the wick which starts the ethanol burning.

The flame from the lighted splint provides the activation energy needed to start the ethanol burning.

What is the activation energy in this experiment?

Tick (✓) two boxes.

$Question 6, shown as an image$

[2]

Answer

(c)

Here are the results of Nina’s experiment.

(c)(i)

Is the reaction endothermic or exothermic?

Use Nina’s results to explain your answer.

[1]

Answer

(c)(ii)

What is the mass of ethanol burned in Nina’s experiment?

[1]

Answer

(c)(iii)

What is the temperature change of the water in Nina’s experiment?

[1]

Answer

(c)(iv)

Calculate the energy that was needed to change the temperature of the water in Nina’s experiment.

Use the equation: Energy change (J) = 4200 × mass of water (kg) × change in temperature (°C)

Give your answer in kJ.

[3]

Answer

Crude oil is a mixture of hydrocarbons.

(a)(i)

Hydrocarbons contain carbon and one other element.

What is the name of the other element?

$Question 7, shown as an image$

bromine chlorine hydrogen oxygen nitrogen

[1]

Answer

(a)(ii)

Most hydrocarbons in crude oil are in the alkanes homologous series.

Which properties of the members in a homologous series are true and which are false

Tick (✓) one box in each row.

[4]

Answer

(a)(iii)

Why is crude oil an important resource for the chemical industry?

Tick (✓) two boxes.

$Question 7, shown as an image$

[2]

Answer

(b)

* Crude oil is separated into fractions using fractional distillation.

The fractional distillation of crude oil is carried out in a fractionating tower.

The table shows some information about the fractions produced by fractional distillation of crude oil.

Fraction	Carbon chain length	Boiling point range (°C)	Height reached in tower
Petroleum gas	1–4	<40	top (lower temperature)
Petrol	5–8	40–110
Naphtha	8–10	110–180
Kerosene	10–16	180–260
Diesel oil	16–20	260–320
Heavy fuel oil	20–50	320–400
Bitumen	>50	>400	bottom (high temperature)

Describe and explain how fractional distillation separates crude oil.

Use data from the table to support your answer.

[6]

Answer

Sundip investigates the rate of reaction between calcium carbonate and hydrochloric acid.

This is the symbol equation for the reaction.

$Question 8, shown as an image$

She adds 50 cm³ of 1 mol / dm³ hydrochloric acid to a flask and puts the flask on a balance.

She adds 10 g of calcium carbonate pieces to the acid.

She measures the mass of the flask and its contents at the start, and again after 1 minute.

Results Mass of flask and contents at the start = 153.2 g Mass of flask and contents after 1 minute = 152.5 g

(a)(i)

Why does the mass of the flask and its contents decrease after 1 minute?

Tick (✓) one box.

$Question 8, shown as an image$

[1]

Answer

(a)(ii)

Calculate the rate of reaction for this experiment.

$Question 8, shown as an image$

Give your answer to 2 significant figures.

Rate of reaction =........ g / s

[3]

Answer

(b)

What can Sundip do to make the reaction faster?

Tick (✓) two boxes.

$Question 8, shown as an image$

[2]

Answer

(c)

Sundip also collects and measures the volume of gas given off during the reaction.

(c)(i)

[2]

Answer

(c)(ii)

[2]

Answer

Elements in the Periodic Table are arranged in order of atomic number.

(a)

The atomic number and relative atomic mass of an element can be used to work out the number of protons, electrons and neutrons in its atoms and ions.

Complete the table.

Use the Data Sheet.

Symbol	Na atom	F^– ion
Atomic number	........................	9
Number of protons	11	9
Number of electrons	........................	........................
Number of neutrons	........................	........................