C2 (Chemistry): Material Choices

This section shows links to revision materials Chemistry C2 - Air Quality.

Overview of Module

Our way of life depends on a wide range of materials produced from natural resources. The Earth’s crust provides us with crude oil, which is a source of fuel and raw material for producing synthetic polymers. Natural polymers can also be useful and can be obtained from living things. This module considers how measurements of the properties of materials can inform the choice of material for a particular purpose. By taking their own measurements, candidates can explore some of the issues that arise when trying to establish accurate and meaningful data.

Key ideas in this module are illustrated through polymers. Candidates learn how the molecules that make up a polymer fit together and how strongly they are bonded to each other, providing an explanation of the properties of materials. This provides an example of a scientific explanation that makes sense of a wide range of observations.

Candidates also learn how polymers can be modified to give them more desirable properties by the introduction of nanoparticles, which have different properties when compared with larger particles of the same material.

Chemistry

C2 - Material Choices (click on the links below for general headings or look below for more detail on what you may be tested on) 

• Measuring properties of materials,
• Crude oil and its uses,
• Structure of materials,
• Nanotechnology

C2.1 How do we measure the properties of materials and why are the results useful?

1. interpret information about how solid materials can differ with respect to properties such as  melting point, strength (in tension or compression), stiffness, hardness and density

2. relate properties to the uses of materials such as plastics, rubbers and fibres

3. relate the effectiveness and durability of a product to the materials used to make it

4. interpret information about the properties of materials such as plastics, rubbers and fibres to assess the suitability of these materials for particular purposes.

C2.2 Why is crude oil important as a source of new materials such as plastics and fibres?

1. recall that the materials we use are chemicals or mixtures of chemicals, and include metals, ceramics and polymers

2. recall that materials can be obtained or made from living things, and give examples such as cotton, paper, silk and wool

3. recall that there are synthetic materials that are alternatives to materials from living things

4. recall that raw materials from the Earth’s crust can be used to make synthetic materials

5. interpret representations of rearrangements of atoms during a chemical reaction

6. understand that in a chemical reaction the numbers of atoms of each element must be the same in the products as in the reactants

7. recall that crude oil consists mainly of hydrocarbons, which are chain molecules of varying lengths made from carbon and hydrogen atoms only

8. recall that only a small percentage of crude oil is used for chemical synthesis and that most is used as fuels

9. understand that the petrochemical industry refines crude oil by fractional distillation; hydrocarbons are separated into fractions of different boiling points, to produce fuels, lubricants and the raw materials for chemical synthesis

10. relate the size of the forces between hydrocarbon molecules to the size of the molecules

11. relate the strength of the forces between hydrocarbon molecules in crude oil to the amount of energy needed for them to break out of a liquid and form a gas, and to the temperature at which the liquid boils

12. understand that some small molecules called monomers can join together to make very long molecules called polymers, and that the process is called polymerisation

13. recall two examples of materials that, because of their superior properties, have replaced materials used in the past.

C2.3 Why does it help to know about the molecular structure of materials such as plastics and fibres?

1. understand that it is possible to produce a wide range of different polymers with properties that make them each suited to a particular use

2. understand how the properties of polymers depend on how their molecules are arranged and held together

3. relate the strength of the forces between the molecules in a polymer to the amount of energy needed to separate them from each other, and therefore to the strength, stiffness, hardness and melting point of the solid

4. understand how modifications in polymers produce changes to their properties (see C2.1), to include modifications such as:

• a. increased chain length
• b. cross-linking
• c. the use of plasticizers
• d. increased crystallinity.

C2.4 What is nanotechnology and why is it important?

1. recall that nanotechnology involves structures that are about the same size as some molecules

2. understand that nanotechnology is the use and control of structures that are very small (1 to100 nanometres in size)

3. understand that nanoparticles can occur naturally (for example in seaspray), by accident (for example as the smallest particulates from combustion of fuels), and by design

4. understand that nanoparticles of a material show different properties compared to larger particles of the same material, and that one of the reasons for this is the much larger surface area of the nanoparticles compared to their volume

5. understand that nanoparticles can be used to modify the properties of materials, and give examples including:

• a. the use of silver nanoparticles to give fibres antibacterial properties
• b. adding nanoparticles to plastics for sports equipment to make them stronger

6. understand that some nanoparticles may have harmful effects on health, and that there is concern that products with nanoparticles are being introduced before these effects have been fully investigated.