We are covering. 1 of 27 Boardworks Ltd From C1 Limestone Extracting Metals Crude Oil Alkanes Alkenes

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1 We are covering 1 of 27 Boardworks Ltd 2006 From C1 Limestone Extracting Metals Crude Oil Alkanes Alkenes

2 Where do building materials come from? 2 of 27 Boardworks Ltd 2006 Buildings are constructed using materials from the Earth. Some cut rocks, including granite, marble and limestone, make excellent building materials. Changing or combining rocks from the Earth provides other useful materials: glass is made from sand and limestone bricks are made from clay cement is made from limestone or clay.

3 What is limestone? 3 of 27 Boardworks Ltd 2006 Limestone is an attractive pale yellow or grey stone. Blocks of cut limestone are used as a material for buildings and statues. Limestone is used during the production of other building materials including: cement glass mortar concrete It is also used to extract impurities from iron in a blast furnace, which produces a useable metal from iron ore.

4 What is cement? 4 of 27 Boardworks Ltd 2006 Cement is used as a binder in concrete and mortar. It is made by heating limestone or clay and adding gypsum (a compound from limestone). This mixture is then ground into a powder. After the powder is mixed with water, it will harden to form a strong glue. Mortar is made from cement, water and sand. It is used in bricklaying and stonework. An even layer of mortar is spread between the bricks or stones to hold them firmly together.

5 What is reinforced concrete? 5 of 27 Boardworks Ltd 2006 Although concrete is a very hard material, it is not very flexible. This means that when it is stretched it can break. Concrete has a low resistance to tension forces. Steel rods are used to increase the strength and flexibility of concrete. This is called reinforced concrete. This material can support 300 to 500 times the combined mass of steel and concrete it is made from. Reinforced concrete has many uses, including lamp-posts, railways and as a structural material to support buildings.

6 How is concrete made? 6 of 27 Boardworks Ltd 2006 Concrete is harder than mortar. It is sometimes described as an artificial rock. Concrete is made from sand, cement and water but it is harder than mortar because it also contains gravel. It is used for the foundations of buildings and for large structures, such as car parks. What is the word equation for making concrete? cement sand gravel water concrete

7 What is thermal decomposition? 7 of 27 Boardworks Ltd 2006 Limestone is a valuable material because it can be used as the starting point for many other materials. When limestone is heated strongly, a chemical reaction takes place. Calcium carbonate breaks down and forms calcium oxide and carbon dioxide. This type of reaction is called thermal decomposition. A lime kiln is often used for this reaction. The limestone is heated to 900 C. This method has been used for centuries. What is the word equation for this reaction? calcium carbonate calcium oxide + carbon dioxide

8 What about other metal carbonates? 8 of 27 Boardworks Ltd 2006 Other metal carbonates can decompose in a similar way to calcium carbonate, when they are heated. For example, when magnesium carbonate is heated it breaks down to form magnesium oxide and carbon dioxide. magnesium carbonate magnesium oxide + carbon dioxide The general equation for the thermal decomposition of a metal carbonate is: metal carbonate metal oxide + carbon dioxide What products are formed when copper carbonate decomposes on heating?

9 How is slaked lime made? 9 of 27 Boardworks Ltd 2006 Calcium oxide, a product of the thermal decomposition of limestone, is also called quicklime. Quicklime is used as an industrial drying agent and to make slaked lime. Uses of slaked lime include glass manufacture and neutralization of the effects of acid rain. Slaked lime is made by adding water to quicklime. The chemical name for slaked lime is calcium hydroxide. What is the word equation for this reaction? calcium oxide + water calcium hydroxide

10 10 of 27 Boardworks Ltd 2006 Why does carbon dioxide turn limewater cloudy? Fully dissolving calcium hydroxide in water forms limewater. Limewater is used to test for carbon dioxide. When carbon dioxide gas is bubbled through limewater, the limewater becomes cloudy. The carbon dioxide reacts with calcium hydroxide to form calcium carbonate and water. The solid calcium carbonate is held in suspension, which gives the limewater a cloudy appearance. What is the word equation for this reaction? calcium hydroxide (aq) carbon calcium + dioxide carbonate + water

11 Summary of uses of limestone products 11 of 27 Boardworks Ltd 2006 The products of limestone have many uses. Quicklime, calcium oxide, is used in making steel and as an industrial drying agent. It can be mixed with water to form slaked lime. Slaked lime, calcium hydroxide, is used to make the building materials mortar and glass. Slaked lime is alkaline. It can be sprayed on agricultural fields to reduce soil acidity and on lakes to neutralize the effects of acid rain. Limewater is made by fully dissolving slaked lime in water. It is often used to test for carbon dioxide. This is because limewater turns cloudy in the presence of carbon dioxide.

12 Summary of limestone chemistry 12 of 27 Boardworks Ltd 2006 Limestone and its products can be involved in various useful chemical reactions: thermal decomposition of limestone calcium carbonate calcium oxide + carbon dioxide production of slaked lime calcium oxide + water calcium hydroxide using limewater to test for carbon dioxide. calcium hydroxide (aq) carbon calcium + dioxide carbonate + water

13 13 of 27 Boardworks Ltd 2006 How does quarrying affect the environment? Limestone is an essential building material. Millions of kilograms of limestone are extracted every year for use in construction and industry. However, quarrying limestone can cause environmental damage. Limestone is often found in areas of outstanding natural beauty. Quarrying can leave scars on the landscape. Explosives used in quarrying produce noise and dust. Air and noise pollution is caused by lorries transporting limestone from the quarry.

14 Impacts of limestone quarrying 14 of 27 Boardworks Ltd 2006

15 15 of 27 Boardworks Ltd 2006 What methods are used to extract metals? Extraction methods vary for different metals. Gold and other unreactive metals occur native. Metals that are found in the ground as uncombined elements do not require further extraction. Most metals are found combined with other elements, as compounds in ores. These metals need to be separated from the other elements that they are combined with using chemical reactions. There are two main ways of extracting metals from their ores: burning ores with carbon (reduction) electrolysis How do mining companies decide which method to use?

16 What is reduction? 16 of 27 Boardworks Ltd 2006 Metals are often found combined with oxygen as oxides. To obtain the metal, the oxygen must be removed. The removal of oxygen from a substance is called reduction. metal oxide (in ore) Carbon can be used to extract metals by reduction. lead oxide + carbon reduction lead metal carbon monoxide PbO C Pb CO In this reaction, the carbon removes oxygen from lead oxide. This occurs because carbon is more reactive than lead. The addition of oxygen to a substance is called oxidation.

17 Reactions of metal oxides and carbon 17 of 27 Boardworks Ltd 2006

18 Extracting iron in industry 18 of 27 Boardworks Ltd 2006

19 Which metals does carbon reduce? 19 of 27 Boardworks Ltd 2006 potassium sodium calcium magnesium aluminium (carbon) zinc iron lead (hydrogen) copper silver gold platinum A metal can be reduced by carbon if it is less reactive than carbon and so appears below carbon in the reactivity series. Certain metals, such as iron, can be only be reduced using carbon if they are heated to very high temperatures. If a metal is more reactive than carbon, other chemical reactions and processes must be used in its extraction. Using the reactivity series, can you name a metal that cannot be extracted from its ore using carbon?

20 20 of 27 Boardworks Ltd 2006 How can the impacts of extraction be reduced? New mining techniques can decrease the effects of metal extraction on the environment. Leaching uses less electricity than traditional mining and does not produce waste gases. Copper ores are treated with and dissolved in dilute sulfuric acid, producing copper sulfate. Electrolysis is then used to extract the copper. Certain bacteria can also be used to dissolve ores and form copper sulfate. Phytomining uses plants to absorb metals from the soil. The process can be used to clean contaminated land. Treating the plants with certain chemicals increases their ability to accumulate minerals in their cells.

21 How can recycling help? 21 of 27 Boardworks Ltd 2006 Metals are easier to recycle than plastic and they retain their original properties, such as conductivity and hardness. Recycling uses up to 95% less electricity than producing metals from ores. Recycling costs less than extracting metals and can be profitable. Recycling creates less waste and reduces the number of sites that have to be mined. One problem is that metallic materials in recycled objects are often mixtures of different metals. This can mean that obtaining pure metals from recycling is more expensive, as it may use more electricity than extracting metals from ores.

22 What is crude oil? 22 of 27 Boardworks Ltd 2006 Crude oil is a fossil fuel and one of the most important substances in the world. It is a mixture of hundreds of different compounds. Crude oil is used to make fuels for transport, heating and generating electricity. It is also used to make plastics and hundreds of different types of chemicals. Every day, the world uses over 70 million barrels of oil. If you filled bath tubs with this amount of oil and put them end-toend, they would stretch round the Earth 7.5 times!

23 How was crude oil made? 23 of 27 Boardworks Ltd 2006 Crude oil is thought to have been made from the remains of marine plants and animals that died millions of years ago. These remains sank to the bottom of the sea, where they were buried in layers of sand and mud, preventing them from rotting. These layers gradually became sedimentary rock. Over millions of years the layers of rock built up, increasing the heat and pressure. This caused the remains to be broken down into the molecules that form crude oil and natural gas.

24 Hydrocarbons in crude oil 24 of 27 Boardworks Ltd 2006 Many compounds in crude oil only contain the elements carbon and hydrogen. They are called hydrocarbons. Most hydrocarbons in crude oil are compounds called alkanes. Alkanes contain a single chain of carbon atoms with hydrogen atoms bonded along the side.

25 What are alkanes? 25 of 27 Boardworks Ltd 2006 Alkanes are a family of hydrocarbon compounds with the general formula C n H 2n+2. The simplest alkane is methane. It has the formula CH 4. The second simplest alkane is ethane. It has the formula C 2 H 6. The third simplest alkane is propane. It has the formula C 3 H 8.

26 Finding crude oil at sea 26 of 27 Boardworks Ltd 2006 Crude oil is often found trapped in rocks of the sea bed. Oil rigs or drilling platforms are used to drill through the sea bed to obtain the oil. Once the oil has been removed from the sea bed, it is pumped in long pipelines to an oil tanker terminal or an oil refinery on land.

27 Problems with crude oil 27 of 27 Boardworks Ltd 2006 Crude oil is extremely useful but it has several drawbacks: Burning the products of crude oil as fuel produces gases and particles that contribute to global warming and air pollution. Removing oil from the ground, as well as oil spillages and slicks, can be very damaging to wildlife and the environment. The high value of oil means it is sometimes the cause of military conflict, especially because a large amount of oil comes from countries that are politically unstable.

28 How can crude oil be made useful? 28 of 27 Boardworks Ltd 2006 Crude oil itself has no uses it must first be processed or refined. This is done in an oil refinery. The first step is to separate compounds in the oil into groups called fractions. Each fraction contains a mix of compounds with a similar number of carbon atoms.

29 Molecule size and boiling point 29 of 27 Boardworks Ltd 2006 Molecules in crude oil can contain anything from just 1 carbon atom to well over 50. The more carbon atoms in a hydrocarbon molecule, the larger the molecule. How does this affect its boiling point? Generally, the larger a hydrocarbon, the higher its boiling point. This is because the intermolecular forces between large molecules are stronger than the intermolecular forces between small molecules. More energy is needed to break the forces between large molecules, and so the boiling point is higher.

30 What is fractional distillation? 30 of 27 Boardworks Ltd 2006 Fractional distillation is a process used to separate a mixture of liquids that have different boiling points. When the mixture is heated, liquids with a low boiling point evaporate and turn to vapour. Liquids with a higher boiling point remain as liquid. The vapour can then be separated from the liquid. Fractional distillation is used to separate crude oil into fractions with different boiling points. It can be done industrially and in the laboratory.

31 Fractional distillation of crude oil 31 of 27 Boardworks Ltd 2006 Crude oil is separated into fractions by fractional distillation. 1. Oil is heated to about 450 C and pumped into the bottom of a tall tower called a fractionating column, where it vaporizes. 2. The column is very hot at the bottom but much cooler at the top. As the vaporized oil rises, it cools and condenses. 3. Heavy fractions (containing large molecules) have a high boiling point and condense near the bottom of the column. 4. Lighter fractions (containing small molecules) have a lower boiling point and condense further up the column.

32 How does fractional distillation work? 32 of 27 Boardworks Ltd 2006

33 Order of fractions 33 of 27 Boardworks Ltd 2006

34 Supply and demand 34 of 27 Boardworks Ltd 2006 The amount of each type of fraction obtained by fractional distillation does not usually match the amount of each fraction that is needed. The large hydrocarbon molecules in the heavier fractions can be broken down into smaller, more useful, molecules to meet demand for raw materials for fuels and plastics. Crude oil often contains more heavier fractions than lighter fractions. Lighter fractions are more useful and therefore more desirable.

35 Catalytic cracking 35 of 27 Boardworks Ltd 2006 Large hydrocarbon molecules can be broken down into smaller molecules using a catalyst. This is called catalytic cracking, and is an example of a thermal decomposition reaction. The hydrocarbon molecules are heated until they turn into vapour, and then mixed with a catalyst. The molecules break apart, forming smaller alkanes and alkenes. Alkenes are reactive molecules that are used to make plastics and other chemicals.

36 What are alkenes? 36 of 27 Boardworks Ltd 2006 Alkenes are a family of hydrocarbon compounds with the general formula C n H 2n. Alkenes are very similar to alkanes, but they have one important difference: they contain at least one double covalent bond between carbon atoms. The simplest alkene is ethene. It has the formula C 2 H 4. The second simplest alkene is propene. It has the formula C 3 H 6.

37 Cracking decane 37 of 27 Boardworks Ltd 2006 Decane from the naphtha fraction can be cracked to form pentane (for use in petrol), propene and ethene. decane (C 10 H 22 ) + + pentane (C 5 H 12 ) propene (C 3 H 6 ) ethene (C 2 H 4 )

38 Saturated vs. unsaturated 38 of 27 Boardworks Ltd 2006 Alkanes are examples of saturated compounds. A saturated compound only contains single covalent bonds between carbon atoms. Alkenes are examples of unsaturated compounds. An unsaturated compound contains at least one double covalent bond between carbon atoms. A test to distinguish between saturated and unsaturated compounds is to add red bromine water. In the presence of unsaturated compounds, the red colour disappears.

39 How does catalytic cracking work? 39 of 27 Boardworks Ltd 2006

40 Catalytic cracking in the lab 40 of 27 Boardworks Ltd 2006 Catalytic cracking can be done in the laboratory by heating mineral wool soaked in oil with a catalyst, producing a gas. aluminium oxide catalyst gaseous product mineral wool soaked in oil What might this gas be?

41 The stages of fractional distillation 41 of 27 Boardworks Ltd 2006

42 What you need to do at home 42 of 27 Boardworks Ltd 2006 Metals their properties and what they are used for Aluminium Copper Titanium Iron and Steel What an alloy is What each is used for What the differences are

43 43 of 27 Boardworks Ltd 2006