|How do geologists track the movement of tectonic plates?
|They use magnetic clues in the rocks. When magnetite in lava is fixed into a position when the rock has cooled enough. The magnetisation lines up in the direction of the Earth's magnetic field at the time. By measuring the angle at which the crystals are magnetised in rocks, they can work out the latitude at which the rock was originally formed.
|How was coal formed?
|River deltas created swamp land. Tree ferns grew in the swamps. As the plants dies, they formed a layer of peat, which was covered by sediment, compressed, heated, and turned to coal. Mountain building then pushed the rocks up to the surface.
|How was limestone formed?
|As plants and animals died in the clear seas, they sank to the bottom and formed fossils in the limestone.
|How was salt formed?
|Seawater moved inland and created shallow salt marshes. Deposits of rock salts formed as the water evaporated.
|How do geologists study sedimentary rocks to find evidence of the conditions under which they were formed?
|Fossils: Give a time scale to the formation of the rock. Shapes of grains: The shape of sand rains in the rocks varies depending on whether the rock was water borne or air blown. Ripples: Show that the rock was formed in the sea or a river.
|Where do chemical industries grow up?
|In areas where resources are available locally. Eg, salt, limestone, and coal in North West England.
|What is salt (sodium chloride) used for?
|- It preserves food, and adds flavour. - It is a source of chemicals (such as chlorine). - It is used to treat icy roads in winter.
|Where can salt be obtained from?
|The sea, or from underground salt deposits.
|How can underground salt be obtained by mining?
|Miners use giant machines to extract rock salt. The rock is 90% sodium chloride. However, the salt does not need to be pure.
|How can salt be obtained by solution mining?
|Water is pumped down into the rock. the salt dissolves and is carried to the surface in solution. The impurities do not dissolve and stay underground. The water is evaporated to extract the salt from the brine.
|How can the methods of obtaining salt have an impact on the environment?
|Uncontrolled solution mining crates very large underground holes. This leads to subsistence and flooding land. From time to time, the land collapses.
|What are the advantages of adding salt to food?
|It is used to add flavour, as well as preserve and process food. Also, salt is an essential part of a healthy diet.
|What are the health implications of eating too much salt?
|- Raises blood pressure - Increases risk of heart disease
|What are the roles of Government departments, such as the Department of Health?
|a) They carry out risk assessments in relation to chemicals in foods. b) They advise the public in relation to the effect of food on health.
|What were alkalis used for before industrialisation?
|- Neuturalising acidic soils - Making chemicals that bind natural dyes to cloth - Converting fats and oils into soap - Manufacturing glass
|What are some traditional sources of alkali?
|- Burnt Wood - Stale Urine
|What do alkalis make when they neutralise acids?
|What are soluble hydroxides and carbonates?
|What are the products when an alkaline hydroxide reacts with acid?
|Salt + Water
|What are the products when an alkaline carbonate reacts with acid?
|Salt + Carbon Dioxide + Water
|What happened in the 19th Century?
|Increased industrialisation lead to a shortage of alkali.
|What were the harmful effects of the Leblanc process?
|It used reacted salt and limestone to make alkali, using coal as a fuel. For every tonne of sodium carbonate produced, it created two tonnes of solid waste, and a tonne of hydrogen chloride gas (acidic). The solid waste slowly released a toxic and foul smelling gas, hydrogen sulfide.
|How can pollution products sometimes be solved?
|By turning the waste products into useful chemicals. For example, The hydrogen chloride produced in the Leblanc process is oxidised to form chlorine.
|The properties of a _________ are completely different from the __________ from which it is made.
|What is chlorine used for?
|Killing microorganisms in domestic water supplies, and as a bleach.
|How did the introduction of chlorine to treat drinking water make a difference to public health?
|There was a steep decline in deaths from typhoid.
|What may the disadvantages of chlorinating water be?
|Chlorination can lead to the formation of THMs. THMs could be absorbed by people, and lead to some forms of cancer.
|What is electrolysis?
|A chemical change, forming new chemicals, bought about by an electric current.
|How is chlorine now obtained?
|By the electrolysis of salt solution (brine).
|What are the uses of the chlorine, sodium hydroxide, and hydrogen produced by electrolysis of brine?
|Chlorine: Treats drinking water, makes bleach, makes hydrochloric acid, makes plastics, makes solvents. Sodium Hydroxide: Makes bleach, makes soap, makes paper, processes food products, removes pollutants from water, makes fibres. Hydrogen: Makes hydrochloric acid, used as a fuel to produce steam.
|Why do some toxic chemicals cause problems?
|They persist in the environment, can be carried over large distances, and may accumulate in food and human tissues.
|What is PVC?
|A polymer that contains chlorine as well as carbon and hydrogen.
|What are the risks of using plasticisers?
|They can leach out from the plastic into the surroundings where they may have harmful effects. Eg. leaching out of a toy into the saliva of the child who chews it.
|What is a Life Cycle Assessment?
|A measure of the use of resources including water, energy input or output, and environmental impact, of a product's life.
|What are the four stages of a Life Cycle Assessment?
|1) Making the material from natural raw materials 2) Making the product from the material 3) Using the product 4) Disposing of the product