Types of Substance (Edexcel GCSE Chemistry)

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.

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

The formula of aluminium oxide is Al₂O₃.

(1)

(1)

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

Figure 5

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.

(1)

(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.  

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

Calcium and potassium react with water in similar ways.

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-;

[1]

[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.