Types of Substance (Edexcel GCSE Chemistry)

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?

Carbon dioxide, diamond and graphite all have covalent structures.

Figure 1 shows their structure.

Figure 1

Carbon dioxide has a melting point of -57°C.

Diamond has a melting point of around 4500°C.

Explain this difference in terms of bonding.

Predict if the melting point of graphite is closer to that of diamond or carbon dioxide.

Give a reason for your answer.

Graphite is used as a lubricant.

Explain how its structure makes it good at this job.

A single layer of graphite is called graphene.

Explain why graphene is a good conductor of electricity.

Table 1 shows information about two different substances, A and B.

Table 1

One of these substances is ionic and one is giant covalent.

Deduce, using the information in Table 1, which substance is which.

Explain the properties of A and B in terms of their structure.

Metals have a metallic structure.

Give two properties of a typical metal.

All metals are malleable.

i) Define malleable.

[1]

ii) Use the structure of metals to explain why they are malleable.

[1]

Figure 1 shows two different fullerenes.

                Buckminsterfullerene                 Carbon nanotube

Figure 1

Describe what a fullerene is.

Fullerenes have many uses. Explain how their structure makes them suitable for each job:

i) Drug delivery

[1]

ii) Increasing the efficiency of a catalyst

[1]

Buckminsterfullerene has a low melting point.

Suggest why, in terms of its structure.

Carbon nanotubes are used to make tennis racket frames.

Suggest why, using structure and bonding.

This question is about polymers.

Figure 1 shows the reaction used to make the polymer poly(ethene).

Figure 1

Complete Figure 1 to show the structure of poly(ethene).

Name this reaction.

Poly(ethene) is a solid at room temperature.

Suggest why in terms of its structure and bonding.

There are two types of poly(ethene). These are shown in Figure 2.

                                      Type A                                                                                                Type B

Figure 2

Identify which type of poly(ethene) has the highest density.

Give a reason for your answer.

 Figure 1 shows two different models, X and Y, that represent an ionic structure.

                                                           X                                                                   Y

Figure 1

What do the different colour spheres represent in the models?

Evaluate model X.

You should mention the advantages and limitations.

Table 1 shows the melting points for two different ionic substances.

 Table 1

Suggest a reason for the difference in melting points.

The melting point of sodium fluoride (NaF) is 992°C.

Predict if the melting point of rubidium fluoride (RbF) is higher or lower.

Give a reason for your answer.