Edexcel GCSE Combined Science Paper 3: Chemistry 1 Foundation November 2021 question paper 1SC0/1CF

If liquid water is cooled below 0 °C it turns into the solid, ice.

Give the name for the change of state from liquid to solid.

Here are five statements about ice and water.

Place ticks in boxes by the two statements that are correct.

Figure 1 shows a label from a bottle of drinking water.

Explain why this drinking water should not be described as pure water.

State the information from Figure 1 that shows that the drinking water is neutral.

Calculate the mass of calcium ions in 250 cm³ of this drinking water.

mass =_........ mg

State how you know that calcium is a metal from its position in the periodic table.

When chromium reacts with oxygen, chromium oxide is formed.

Write the word equation for this reaction.

What type of reaction occurs when chromium reacts with oxygen?

Calculate the relative formula mass of chromium oxide, Cr₂O₃.

(relative atomic masses: O = 16, Cr = 52)

relative formula mass =_........

Three different metals are added to separate test tubes of acid.

The observations are shown in Figure 2.

Place the metals in order of reactivity from most to least reactive.

most reactive_........

Hydrogen is given off when magnesium reacts with acid. The hydrogen is tested by collecting the gas in a test tube and igniting it.

What is the safest way to ignite the gas?

State the observation made in this test that shows that the gas is hydrogen.

Iron is extracted by heating iron oxide with carbon. Electrolysis of molten iron oxide is not used to extract iron.

State why iron can be extracted by heating iron oxide with carbon.

State why electrolysis is not used to extract iron.

Ammonia is made by reacting nitrogen with hydrogen.

The nitrogen and hydrogen are obtained from raw materials.

Draw one straight line from each gas to the raw material it is obtained from.

When nitrogen and hydrogen are reacted together, the reaction can reach a dynamic equilibrium.

Use words from the box to complete the sentences about dynamic equilibrium.

In a dynamic equilibrium two reactions occur at the same time.

These are the forward reaction and the_........ reaction.

The rates of the two reactions are_........ .

The reaction between nitrogen and hydrogen happens at a pressure of 200 atmospheres.

Another unit of pressure is Pascals, Pa (1 atmosphere = 101 325 Pa).

Calculate the value of 200 atmospheres in Pascals.

pressure =_........ Pa

Figure 3 shows molecules of nitrogen, hydrogen and ammonia before the reaction and at equilibrium.

Complete the table showing

• the number of hydrogen molecules before reaction

• the number of hydrogen molecules at equilibrium

• the change in the number of hydrogen molecules.

Hydrochloric acid reacts with solid B. Solid B is an alkali.

A student carries out an experiment to see how the pH changes when different masses of solid B are added to dilute hydrochloric acid.

The student uses the following method.

step 1 use a measuring cylinder to measure out 100cm³ of dilute hydrochloric acid

step 2 pour the acid into a beaker

step 3 measure the pH with a pH probe

step 4 add half a spatula of solid B and stir

step 5 repeat steps 3 and 4 until the pH stops changing.

Give a safety precaution that should be taken during the experiment.

Give an improvement to step 4 that would produce more accurate results.

What is the most likely change in pH during the experiment?

If some methyl orange indicator is added to the acid in step 2, the mixture changes colour during the experiment.

State the colour change.

colour at start in acid_........ colour at end_........

Concentrated hydrochloric acid can be broken down using electricity. The apparatus that can be used is shown in Figure 4.

Give the name of the piece of apparatus labelled X.

The rod labelled Y in Figure 4 is made of graphite.

What is the name of this piece of apparatus?

Give one reason why graphite is a suitable material to make Y.

Complete the balanced equation for the reaction that occurs.

_........ HCl H₂ + Cl₂

The scientist John Dalton lived over 200 years ago.

John Dalton suggested an early model of atoms.

When Dalton first described atoms he said that

• all elements are made of atoms

• atoms are not formed of any smaller particles

• all atoms of the same element are identical.

Give two differences between Dalton’s model of atoms and today’s model of atoms.

Dalton also investigated different gases.

One of the gases that Dalton investigated was ethene.

The structure of one molecule of ethene is shown in Figure 5.

Give the molecular formula and the empirical formula of ethene.

molecular formula_........

empirical formula_........

Another gas that Dalton investigated was chlorine.

Chlorine gas reacts with water. The two products are a solution of hydrogen chloride and the substance HC l O.

Complete the balanced equation for this reaction, including the three missing state symbols.

Hydrogen chloride solution is acidic.

The formulae of four ions are shown in Figure 6.

Give the formula of the ion in Figure 6 that causes the hydrogen chloride solution to be acidic.

formula_........

An acid reacts with an alkali.

Give the name of this type of reaction.

Describe what you would see when some copper carbonate powder is added to a beaker of dilute sulfuric acid.

A sample of potable water contains impurities.

Why is this sample of water potable even though it contains impurities?

Waste water can be used to produce drinking water. The processes used include sedimentation, filtration and chlorination.

What is sedimentation?

State why the waste water is filtered.

State the reason for chlorination.

Some salts can be added to waste water to remove impurities. In an experiment, different masses of salt A were added to 1000cm³ samples of waste water. The experiment was repeated with salt B. The percentages of impurities removed from the waste water are shown in Figure 7.

mass of salt in mg per 1000cm³ water

Figure 7

It was concluded that the best way to purify 1000cm³ of the waste water is to add 100 mg of salt B.

Use the information about salt A and salt B in Figure 7 to evaluate this conclusion.

*(d) A sample of water was contaminated with a dissolved solid.

Devise a plan to separate pure water from this mixture, including a test to show that the water obtained is neutral.

You may use some or all of the apparatus shown in Figure 8 and any other laboratory apparatus.