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© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 37 KS3 Chemistry 9H Using Chemistry.

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Presentation on theme: "© Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 37 KS3 Chemistry 9H Using Chemistry."— Presentation transcript:

1 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 1 of 37 KS3 Chemistry 9H Using Chemistry

2 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 2 of 37 Contents 9H Using Chemistry New materials – everyday reactions Summary activities New materials – industrial processes Chemical reactions Burning fuels

3 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 3 of 37 Chemical reactions everywhere! Chemical reactions take place around you and inside you all the time. How many reactions can you name? Burning, rusting, cooking and living all involve reactions. In a chemical reaction, reactants are changed into products and new materials are formed. Some chemical reactions are carried out to make new materials and some reactions are used to release energy. Are chemical reactions always useful?

4 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 4 of 37 Useful chemical reactions

5 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 5 of 37 Non-useful chemical reactions

6 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 6 of 37 What’s that reaction?

7 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 7 of 37 Contents 9H Using Chemistry New materials – everyday reactions Summary activities New materials – industrial processes Chemical reactions Burning fuels

8 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 8 of 37 Combustion is the chemical reaction that takes place when a substance burns. The substance reacts with oxygen and energy is released as heat and light. Combustion is an important reaction as more than 90% of the world’s energy comes from burning fossil fuels like coal, natural gas and petrol. Where do fossil fuels come from and what other fuels are there? Using combustion

9 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 9 of 37 Fire triangle

10 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 10 of 37 Formation of fossil fuels – coal

11 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 11 of 37 Formation of fossil fuels – oil and gas

12 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 12 of 37 What’s the best fuel?

13 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 13 of 37 Equations for combustion Combustion, as the reaction of substance with oxygen, is also called oxidation. The products of oxidation are oxides. Coal is mostly carbon. The product of burning coal is a gas which turns limewater cloudy. What is the equation for burning coal? carbon dioxide oxygen carbon Many fuels are hydrocarbons, which means they are made up of carbon and hydrogen. When hydrocarbons burn carbon dioxide and water (hydrogen oxide) are produced. What is the equation for burning the hydrocarbon methane? carbon dioxide oxygenmethanewater

14 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 14 of 37 Incomplete combustion A good supply of oxygen is needed for a fuel to burn completely and release as much energy as possible. When carbon reacts completely with oxygen, it is all turned into carbon dioxide. This is called complete combustion: carbon dioxide oxygen carbon If there is not enough oxygen, a fuel cannot burn completely and less energy is released. Some fuel is wasted. When carbon does not react completely with oxygen, the product is carbon monoxide, a colourless poisonous gas. This is called incomplete combustion: carbon monoxide oxygen carbon

15 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 15 of 37 Contents 9H Using Chemistry New materials – everyday reactions Summary activities New materials – industrial processes Chemical reactions Burning fuels

16 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 16 of 37 Rusting reaction Rusting is the reaction of iron with oxygen in the presence of water. Salt helps to speed up the rate of this reaction. Why does iron rust more quickly at the seaside?

17 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 17 of 37 Iron that is exposed to the weather is usually coated with a layer of paint. New products that contain iron are often boxed with a small packet of drying agent. iron oxide  oxygen+iron Preventing rusting Rusting is the reaction of iron with oxygen in the presence of water to form iron oxide (rust). Rusting is an ‘unhelpful’ chemical reaction. How do these measures help to prevent rusting? The paint prevents oxygen and water getting to the iron. The drying agent absorbs any water that may cause rusting.

18 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 18 of 37 Yeast uses oxygen from the air for aerobic respiration: The carbon dioxide gas produced in this reaction makes bread rise by filling it with bubbles. Making bread and alcohol Yeast is a living organism which carries out chemical reactions that are used for making bread and alcohol. Yeast can also carry out respiration without oxygen. This is anaerobic respiration, which is also called fermentation: Fermentation is used to produce alcohol in beer and wine. energy)water+ carbon dioxide  oxygen+glucose(+ energy)ethanol+ carbon dioxide  glucose(+

19 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 19 of 37 Ripening fruit Starch is broken down into sugars increasing sweetness. Acids are neutralized making the apples less sour. The ripening of fruit is a complex collection of chemical reactions. Take apples as an example: Chlorophyll (green) changes to anthocyanin (red). Pectin, a chemical which makes apples hard, is broken down and so makes the apples softer. Why do food producers and supermarkets need to know about the conditions and reactions involved in ripening fruit?

20 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 20 of 37 Ripening fruit The ripening of all fruit and vegetables involves similar chemical reactions. The speed of ripening is affected by the temperature and by the presence of a chemical called ethene. Food producers and supermarkets know the best conditions for slowing down or speeding up the ripening process so that fruit and vegetables do not go off too soon.

21 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 21 of 37 Cooking eggs Cooking involves chemical reactions – changes colour, taste and texture due to atoms in food joining together in new ways. Cooking an egg changes it texture from runny to firm: Eggs contain a protein called albumen. The protein molecules are long chains of amino acids folded into a ball shape. When eggs are heated, some of the protein atoms break apart and the molecules unfold. These molecules then join to other nearby protein molecules until they are all linked in a network.

22 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 22 of 37 Knowing what causes this reaction can help to slow it down: Placing sliced apples in water prevents browning because the apples are no longer exposed to air. The chemical ascorbic acid (vitamin C), found in lemon juice, is also known to prevent the browning reaction. Food spoilage Chemical reactions are not always useful. The changes that take place as food “spoils” are caused by chemical reactions. Apples turn brown when exposed to the air because they react with oxygen in the air.

23 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 23 of 37 Contents 9H Using Chemistry New materials – everyday reactions Summary activities New materials – industrial processes Chemical reactions Burning fuels

24 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 24 of 37 Making plastics from oil Plastics are very useful materials that are made by chemical reactions in factories. The starting materials for making plastics come from crude oil, which is found in the Earth’s crust. When crude oil is pumped out of the ground (or sea bed) it is a mixture of chemicals called hydrocarbons. Crude oil is separated into different hydrocarbons at an oil refinery using a process called fractional distillation.

25 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 25 of 37 Fractional distillation separates crude oil based on the different boiling points of the hydrocarbon molecules. Small molecules boil at lower temperatures than bigger ones. Crude oil and fractional distillation boils at a higher temperature boils at a lower temperature The crude oil is heated and molecules of different sizes boil at different temperatures. These gases are collected separately and cooled, condensing to form different fractions. Some of the fractions obtained from crude oil, listed in order of increasing boiling point, are: fuel gas, petrol, naphtha, kerosine, diesel and bitumen. Which of these fractions has the biggest molecules?

26 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 26 of 37 Fractional distillation animation

27 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 27 of 37 Fractional distillation activity

28 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 28 of 37 Making plastics by polymerization The separated hydrocarbons obtained from the fractional distillation of crude oil have many uses. One of the main uses of the smaller hydrocarbon molecules obtained is to make plastics. Plastics consist of very long chains called polymers. The chemical reaction in which small molecules join together to make these very long polymer molecules is called polymerization.

29 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 29 of 37 Making plastics

30 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 30 of 37 iron oxide +carbon  iron+carbon dioxide This process is the reverse of oxidation as the oxygen is taken away from the metal. It is called a reduction. In the reaction above, the iron oxide is reduced to iron. Making metals by smelting Metals are very useful materials but many metals are found in rocks as compounds called ores. Iron, which is used to make steel, is found in the earth as iron ore. By heating the iron ore (mainly iron oxide) with carbon, the iron can be extracted. The carbon displaces the metal in a process called smelting.

31 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 31 of 37 Blast furnace animation

32 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 32 of 37 oxygen + aluminium  aluminium oxide During electrolysis, the metal is always formed as a coating on the electrode that is connected to the negative electrode (the cathode.) Electrolysis Electrolysis is a chemical reaction that uses electricity to break up a compound and is another method for extracting a metal from its ore. For example, aluminium cannot be extracted by smelting and so electrolysis is used to aluminium metal from aluminium oxide. This is why electrolysis is also used for the purification of copper and for electroplating other metals.

33 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 33 of 37 Electrolysis animation

34 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 34 of 37 Contents 9H Using Chemistry New materials – everyday reactions Summary activities New materials – industrial processes Chemical reactions Burning fuels

35 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 35 of 37 Glossary combustion – The reaction of a substance with oxygen which releases heat and light energy. electrolysis – A reaction that uses electricity to break up a compound and can be used for extracting metal. fuel – A substance that is burnt to provide energy. fractional distillation – The process used to separate a mixture, such as crude oil, into its components which have different boiling points. hydrocarbons – Compounds that are made up of the elements carbon and hydrogen only. polymers – Materials, such as plastics, that are made up of very long molecules. smelting – Heating a metal ore with carbon to extract the pure metal.

36 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 36 of 37 Anagrams

37 © Boardworks Ltd 2004 1 of 20 © Boardworks Ltd 2005 37 of 37 Multiple-choice quiz


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