C3 (Chemistry): Chemicals in our lives

This section shows links to revision materials Chemistry C3 - Chemicals in our lives - risks and benefits

Overview of Module

Thanks to its geological history, Britain is a country that has large deposits of valuable resources including salt and limestone as well as coal, gas and oil. These raw materials have been the basis of a chemical industry for over 200 years. At first many of the industrial processes were highly polluting. This led to new laws and the establishment of regulatory organisations to control the industry. Today the industry is under great pressure to operate processes that are efficient in their use of energy and which do minimal harm to health and the environment.

Salt is particularly important. Salt is necessary in the diet but is hazardous if eaten to excess.  Chemists have learnt to convert salt to alkalis and to chlorine, chemicals that are used to make many valuable products.

The use of manufactured chemicals has brought both benefits and risks. Society has become increasingly concerned that there are many chemicals that are used in large amounts, but which have never been thoroughly tested to evaluate their effects on people and the environment.

The data from Life Cycle Assessments shows that in selecting a product for a particular job we should assess not only its ‘fitness for purpose’ but also the total effects of using the materials that make up the product over its complete life cycle, from its production using raw materials to its disposal.

Chemistry

C3 - Chemistry in our lives (click on the links below for general headings or look below for more detail on what you may be tested on)

• Minerals in Britain,
• The importance of salt,
• Manufacture and use of chemicals,
• Safety and sustainability

C3.1 What were the origins of minerals in Britain that contribute to our economic wealth?

1. understand that geologists explain most of the past history of the surface of the Earth in terms of processes than can be observed today

2. understand that movements of tectonic plates mean that the parts of ancient continents that now make up Britain have moved over the surface of the Earth

3. understand how geologists use magnetic clues in rocks to track the very slow movement of the continents over the surface of the Earth

4. understand that the movements of continents means that different rocks in Britain formed in different climates

5. understand how processes such as mountain building, erosion, sedimentation, dissolving and evaporation have led to the formation of valuable resources found in England including coal, limestone and salt

6. understand how geologists study sedimentary rocks to find evidence of the conditions under which they were formed, to include:

• a. fossils
• b. shapes of water borne grains compared to air blown grains
• c. presence of shell fragments
• d. ripples from sea or river bottom

7. understand that chemical industries grow up where resources are available locally, e.g. salt, limestone and coal in north west England.

C3.2 Where does salt come from and why is it so important?

1. understand the importance of salt (sodium chloride) for the food industry, as a source of  chemicals and to treat roads in winter

2. recall that salt can be obtained from the sea or from underground salt deposits

3. understand how underground salt can be obtained by mining, or by solution in water

4. understand why the method used to obtain salt may depend on how the salt is to be used

5. understand how the methods of obtaining salt can have an impact on the environment

6. understand the advantages of adding salt to food as flavouring and as a preservative

7. recall the health implications of eating too much salt

8. be able to evaluate data related to the content of salt in food and health

9. recall that Government departments, such as the Department of Health and the Department for Environment, Food and Rural Affairs, have a role in:

• a. carrying out risk assessments in relation to chemicals in food
• b. advising the public in relation to the effect of food on health.

C3.3 Why do we need chemicals such as alkalis and chlorine and how do we make them?

1. recall that, even before industrialisation, alkalis were needed to neutralise acid soils, make chemicals that bind natural dyes to cloth, convert fats and oils into soap and to manufacture glass

2. recall that traditional sources of alkali included burnt wood or stale urine

3. understand that alkalis neutralise acids to make salts

4. recall that soluble hydroxides and carbonates are alkalis

5. predict the products of the reactions of soluble hydroxides and carbonates with acids

6. understand that increased industrialisation led to a shortage of alkali in the nineteenth century

7. understand that the first process for manufacturing alkali from salt and limestone using coal as a fuel caused pollution by releasing large volumes of an acid gas (hydrogen chloride) and creating great heaps of waste that slowly released a toxic and foul smelling gas (hydrogen 

sulfide)

8. understand that pollution problems can sometimes be solved by turning wastes into useful chemicals

9. understand that oxidation can convert hydrogen chloride to chlorine, and that the properties of a compound are completely different from the elements from which it is made

10. recall that chlorine is used to kill microorganisms in domestic water supplies and as a bleach

11. understand how the introduction of chlorination to treat drinking water made a major contribution to public health

12. interpret data about the effects of polluted water on health and the impact of water treatment with chlorine to control disease

13. understand that there may be disadvantages of chlorinating drinking water, including possible health problems from traces of chemicals formed by reaction of chlorine with organic materials in the water

14. understand that an electric current can be used to bring about chemical change and make new chemicals through a process called electrolysis

15. recall that chlorine is now obtained by the electrolysis of salt solution (brine). NOTE: Technical details and the ionic reactions are not required

16. recall examples of important uses by industry of the sodium hydroxide, chlorine and hydrogen produced by electrolysis of brine

17. interpret data about the environmental impact of the large scale electrolysis of brine.

C3.4 What can we do to make our use of chemicals safe and sustainable?

1. understand that there is a large number of industrial chemicals with many widespread uses, including consumer products, for which there is inadequate data to judge whether they are likely to present a risk to the environment and/or human health

2. understand that some toxic chemicals cause problems because they persist in the environment, can be carried over large distances, and may accumulate in food and human tissues

3. recall that PVC is a polymer that contains chlorine as well as carbon and hydrogen

4. understand that the plasticizers used to modify the properties of PVC can leach out from the plastic into the surroundings where they may have harmful effects

5. understand that a Life Cycle Assessment (LCA) involves consideration of the use of resources including water, the energy input or output, and the environmental impact, of each of these stages:

• a. making the material from natural raw materials
• b. making the product from the material
• c. using the product
• d. disposing of the product

6. when given appropriate information from a Life Cycle Assessment (LCA), compare and evaluate the use of different materials for the same purpose.