Types of Substance (Edexcel GCSE Combined Science: Chemistry): Exam Questions

Why can graphite conduct electricity? 

In the 19th century, Mendeleev arranged the elements known at the time to form his periodic table. Mendeleev’s periodic table is different from the modern periodic table.

State one difference between Mendeleev’s periodic table and the modern periodic table.

Aluminium oxide reacts with hydrochloric acid to form a salt and water.

i) State the name of the salt formed.

(1)

ii) In this reaction aluminium oxide is a base. State the type of reaction that takes place when an acid reacts with a base.

(1)

Gallium, Ga, is in the same group of the modern periodic table as aluminium.

The formula of aluminium oxide is Al₂O₃.

i) Predict the formula of gallium oxide.

(1)

ii) Gallium oxide has a very high melting point. Gallium oxide does not conduct electricity when solid but does conduct electricity when molten.

What type of substance is gallium oxide?

(1)

Figure 5 shows the changes of state for gallium and the arrangement of particles in liquid gallium.

Figure 5

i) Complete the boxes for solid gallium and gaseous gallium by drawing the arrangement of the particles in each of these physical states.

(2)

ii) Give the name of the change of state labelled Y in Figure 5.

(1)

Gallium metal is a conductor of electricity.

Explain how metals conduct electricity.

Which statement about diamond is correct? 

An ion of element X can be represented as

^2–

This ion of element X has 54 electrons.

Calculate the number of protons and the number of neutrons in this ion.

number of protons ............................................................... number of neutrons ..............................................................

Higher Only

A sample of silicon contains isotopes.

i) State, in terms of subatomic particles, how atoms of these isotopes are the same.

(1)

ii) This sample of silicon contains three isotopes.

92% of the atoms are silicon-28

5% of the atoms are silicon-29

3% of the atoms are silicon-30

Calculate the relative atomic mass of silicon in this sample.

(2)

relative atomic mass = ...............................................................

Figure 6 shows some properties of three substances, A, B and C.

Figure 6

Deduce, using the information in Figure 6, the structure and bonding of substances A, B and C, explaining their properties in terms of their structure and bonding.

Fullerenes are molecules made of carbon.

Fullerenes are increasingly used as catalysts due to their large surface area.

Give one other use of fullerenes.  

Different substances have characteristic melting and boiling points, depending on the strength of the bonds or forces holding them together.

Which explains why methane has a lower melting point than sodium chloride? 

This question is about alkenes and polymers.

Ethene (C₂H₄) can be represented by different types of formula.

 Complete the table by giving the missing information. 

Ethene is used to make poly(ethene).

i) State the type of polymerisation used to form poly(ethene).

(1)

ii) Complete the equation for the polymerisation of ethene.

(2)

The diagram shows the repeat unit of another polymer.

Draw the displayed formula of the monomer used to make this polymer.

Poly(ethene) is used to make plastic bags.

Corn starch from plants can also be used to make polymers for plastic bags.

The table gives some information about poly(ethene) and polymers made from corn starch.

Use the information in the table and your knowledge to discuss the advantages and disadvantages of using poly(ethene) to make plastic bags.

Sodium chloride is often known as 'table salt'. 

Which compound represents sodium chloride? 

A student used the equipment in Figure 1 to investigate whether electricity can pass through solids and through solutions.

Figure 1

Suggest why a lamp is included in the circuit.

Copper wires are used to connect the circuit.

 i) Describe the structure and bonding in copper.

 (4)

ii) Explain how copper is able to conduct electricity.

 (1)

The student used graphite for the electrodes in this experiment.

Suggest two reasons why graphite is a suitable material to use as the electrodes.

The student tested 2 solids and their solutions. Figure 2 shows the results of the investigation.

Figure 2

Explain the results of the investigation.

Covalent molecules can be displayed using a variety of diagrams and written formulae.

Which of the following shows the number of non-bonding electrons present in a molecule?

Calcium has an atomic number of 20. A calcium atom has a mass number of 40.

i) Which row of the table shows the number of protons and number of neutrons in this atom of calcium?

(1)

ii) Figure 8 shows the arrangement of electrons in an atom of calcium.

Figure 8

Explain, using the information in Figure 8, in which period of the periodic table calcium can be found.

(2)

Calcium and potassium react with water in similar ways.

i) One similarity in the reactions is that hydrogen gas is produced.

State one other similarity in the products of the reactions of calcium and potassium with water.

(1)

ii) Potassium is higher in the reactivity series than calcium and reacts more vigorously with water than calcium reacts with water.

State why potassium is higher in the reactivity series and reacts more vigorously with water than calcium.

(1)

Calcium chloride can be prepared by the reaction of calcium with chlorine gas.

Figure 9 shows some properties of calcium, chlorine and calcium chloride.

Figure 9

Explain, in terms of bonding and structure, why the properties of the product, calcium chloride, are different from the properties of the reactants, calcium and chlorine.

A student carried out the electrolysis of copper chloride solution using graphite electrodes.

Figure 1 shows the apparatus they used.

Figure 1

Explain why copper chloride solution, rather than solid copper chloride was used.

Cu²⁺ and H⁺ ions are attracted to the cathode.

State the ions attracted to the anode.

Graphite electrodes are chosen because they are inert and can conduct electricity.

Explain why it is important inert electrodes are used.

Explain, in terms of its structure, how graphite can conduct electricity

Cobalt is a transition metal.

Cobalt has the atomic number 27.
State one thing this tells you about cobalt atoms.

 Describe the structure of cobalt.

Cobalt’s melting point is 1495°C.

Explain why cobalt has a high melting point, using its structure.

Alloys can be made by mixing other metals, such as chromium, with cobalt.

Figure 1 shows the difference in structure between pure cobalt and an alloy.

Figure 1

Use Figure 1 to explain why a cobalt and chromium alloy is less malleable than pure cobalt.

This question is about three substances: calcium, calcium chloride and calcium carbonate.

Calcium chloride and calcium carbonate contain ions: Ca²⁺, Cl^- and CO₃^2-;

i) Give the formula of calcium chloride

[1]

ii) Give the formula of calcium carbonate.

[1]

At room temperature, calcium can conduct electricity but calcium chloride cannot.

Use their structure to explain why.

Explain what you could do to prove that dissolving calcium chloride in water will allow it to conduct electricity.

Calcium carbonate is insoluble in water.

Describe what you would have to do to make calcium carbonate conduct electricity.

Explain why this would work.

Figure 1 shows some different ways used to represent the structure of an ammonia molecule.

    Dot and cross diagram               ball and stick diagram               space filling diagram

Figure 1

Draw the displayed formula of ammonia.

Give one advantage of the dot and cross diagram.

Discuss the limitations of the dot and cross and space filling diagrams.

Ammonia has a low boiling point (-33°C).

Explain why, using its structure.