1 Chapter 5Rocks and minerals 5.1Rocks 5.2Extraction of metals from their ores 5.3Limestone, chalk and marble 5.4Weathering and erosion of rocks 5.5Chemical changes involving calcium carbonate Summary Concept map 5.6Tests for calcium carbonate in a sample of limestone/chalk/marble Chapter 5 Rocks and minerals

2 5.1ROCKS WHAT ARE ROCKS AND MINERALS? 5.1 Rocks

3 A ROCK is a solid mass of a mineral or a mixture of minerals. A MINERAL is a naturally occurring solid with a definite crystalline structure and chemical composition. 5.1 Rocks

4 Figure 5.2 Quartz is a mineral. 5.1 Rocks

5 Figure 5.3 The rock granite contains 3 minerals: quartz, feldspar and mica. 5.1 Rocks

6 MetamorphicrocksMetamorphicrocks IgneousrocksIgneousrocks SedimentaryrocksSedimentaryrocks TYPES OF ROCKS Rocks are divided into three types according to their origin. 5.1 Rocks

7 USES OF MINERALS Figure 5.8 Some uses of minerals. Graphite is used to make ‘pencil lead’. Rock salt is used in cooking. 5.1 Rocks

8 Jade is a gemstone used in jewellery. Marble is used as floors in commercial buildings. Figure 5.8 Some uses of minerals. 5.1 Rocks

9 Gold is used in jewellery. Figure 5.8 Some uses of minerals. 5.1 Rocks

10 MINERALS AND ORES An ORE is a mineral from which a constituent (usually a metal) can be profitably extracted. Figure 5.9 Bauxite - the main ore of aluminium. It is mostly aluminium oxide. 5.1 Rocks

11 Figure 5.10 Copper pyrite - the main ore of copper. It is mostly copper iron sulphide. 5.1 Rocks

12 Figure 5.11 Haematite - the main ore of iron. It is mostly iron(III) oxide. 5.1 Rocks

13 Figure 5.12 Galena - the main ore of lead. It is mostly lead(II) sulphide. 5.1 Rocks

14 5.2EXTRACTION OF METALS FROM THEIR ORES EXTRACTING METALS Metal ore Compound of the metal MineralsImpurities Mixed with 5.2 Extraction of metals from their ores

15 1. Mining of the ore 2. Concentrating the ore 3. Extraction of the metal from the concentrated ore 4. Purification of the impure metal To obtain a pure metal from its ore 5.2 Extraction of metals from their ores

16 concentrate extract purify ore in the ground concentrated ore, with little waste pure metal impure metal ore mixed with waste rock etc. Figure 5.13 Extracting a metal from its ore. dig up 5.2 Extraction of metals from their ores

17 Extraction of iron from haematiteiron(III) oxide + carboniron + carbon dioxide heat (coke) Extraction of aluminium from bauxite aluminium oxidealuminium + oxygen electrolysis 5.2 Extraction of metals from their ores

18 LIMITED RESERVES OF NATURAL RESOURCES LimitedLimited Non-renewableNon-renewable WE MUST USE MATERIALS WISELY! 5.2 Extraction of metals from their ores

19 5.3LIMESTONE, CHALK AND MARBLE ROCKS CONTAINING CALCITE Figure 5.14 Limestone. 5.3 Limestone, chalk and marble

20 Figure 5.15 Chalk. 5.3 Limestone, chalk and marble

21 Figure 5.16 Marble. 5.3 Limestone, chalk and marble

22 In common Contain the same mineral calcite Appearance Hardness DifferentDifferent 5.3 Limestone, chalk and marble Limestone, chalk and marble are common rocks.

23 HOW WERE LIMESTONE, CHALK AND MARBLE FORMED? 5.3 Limestone, chalk and marble 1.Millions of years ago, oceans were filled with sea creatures having shells. 1.Millions of years ago, oceans were filled with sea creatures having shells. 2.When they died, the remains built up a thick deposit on ocean beds. 3.These deposits were under great pressure and turned into limestone or chalk. 3.These deposits were under great pressure and turned into limestone or chalk. 4.As the Earth’s crust moved, these mineral deposits were pushed upward and formed hills.

24 Movement of the Earth’s crust raised the limestone out of the sea floor to form this hill by the seashore. 5.3 Limestone, chalk and marble

25 Formation of limestone. 5.3 Limestone, chalk and marble

26 USES OF LIMESTONE Figure 5.19 A footpath made of limestone. 5.3 Limestone, chalk and marble

27 Figure 5.20 Limestone is a raw material for making cement. 5.3 Limestone, chalk and marble

28 Figure 5.21 The outside wall of this building is made of glass. Limestone is used in glass making. 5.3 Limestone, chalk and marble

29 limestone paper cement cement mortar steel glass buildings and roads concrete concrete slaked lime neutralizes acidic soil Figure 5.22 Uses of limestone. 5.3 Limestone, chalk and marble

30 5.4WEATHERING AND EROSION OF ROCKS WEATHERING AND EROSION WEATHERING of rocks is the slow process (usually over thousands of years) in which exposed rocks are broken down into smaller pieces. Weathering occurs through the actions of water, wind, air and changes in temperature. 5.4 Weathering and erosion of rocks

31 EROSION of rocks is the slow process in which weathered rock pieces are transported away by gravity, wind and water. Erosion also refer to the process which involves weathering of rocks and transportation of weathered rock pieces to another place. 5.4 Weathering and erosion of rocks

32 Figure 5.23 The Great Wall of China has been continuously weathered during the past 2200 years. 5.4 Weathering and erosion of rocks

33 Figure 5.24 Wind erosion caused this unusual limestone formation. 5.4 Weathering and erosion of rocks

34 Figure 5.24 This gorge was formed by eroding action of the river. 5.4 Weathering and erosion of rocks

35 TYPES OF WEATHERING Physicalweathering Chemicalweathering 5.4 Weathering and erosion of rocks

36 PHYSICAL WEATHERING 2. Cool down and contract quickly at night 2. Cool down and contract quickly at night ROCKSBREAK!ROCKSBREAK! Weathering by temperature changes 5.4 Weathering and erosion of rocks 1. Rocks get hot and expand and expand in daytime 1. Rocks get hot and expand and expand in daytime

37 Figure 5.25 Rocks in deserts are badly weathered, partly due to big day-and-night temperature changes. 5.4 Weathering and erosion of rocks

38 Weathering by frost action Figure 5.26 Expanding ice breaks rocks. Rainwater gathers in crack Rock The crack gets bigger Ice Eventually a piece of rock breaks off Temperature falls below 0 C 。 5.4 Weathering and erosion of rocks

39 Weathering by abrasion Breaking down and grinding away of rocks Breaking down and grinding away of rocks WINDWIND WAVESWAVES FASTMOVINGSTREAMSFASTMOVINGSTREAMS 5.4 Weathering and erosion of rocks

40 Figure 5.27 A fast-moving stream acts like sandpaper to grind rocks. 5.4 Weathering and erosion of rocks

41 CHEMICAL WEATHERING Attack by acid water calcium carbonate calciumhydrogencarbonate carbon dioxide carbonic acid Weathering and erosion of rocks

42 Calcium hydrogencarbonate is soluble in water and thus the limestone is slowly worn away. 5.4 Weathering and erosion of rocks

43 Figure 5.28 A sinkhole in limestone area. 5.4 Weathering and erosion of rocks

44 Figure 5.29 This limestone statue has been chemically weathered by rain. 5.4 Weathering and erosion of rocks

45 Attack by oxygen Oxygen in air can attack some rocks, especially those containing iron. This causes the rock to wear away slowly. Figure 5.30 Air can oxidize rocks containing iron, causing a brown colour. 5.4 Weathering and erosion of rocks

46 SOIL RocksRocks SmallerparticlesSmallerparticles SoilSoil break down into and become 5.4 Weathering and erosion of rocks

47 Figure 5.32 Soil is a mixture of small rock particles, air, water and humus. 5.4 Weathering and erosion of rocks

48 5.5CHEMICAL CHANGES INVOLVING CALCIUM CARBONATE THERMAL DECOMPOSITION OF CALCIUM CARBONATE Carbondioxide Calciumoxide Calciumcarbonate No visible change change strong heating gentle heating 5.5 Chemical changes involving calcium carbonate

49 Figure 5.33 Heating calcium carbonate strongly. test tube holder calcium carbonate Bunsen burner roaring non- luminous flame 5.5 Chemical changes involving calcium carbonate

50 Calcium oxide is commonly known as quicklime. CalciumoxideCalciumoxide + HeatHeat CalciumhydroxideCalciumhydroxide (Slaked lime) Chemical changes involving calcium carbonate

51 CalciumhydroxideCalciumhydroxide Whitesuspension is formed Whitesuspension filter Limewater is formed Limewater is formed Chemical changes involving calcium carbonate

52 LIMEWATER TEST FOR CARBON DIOXIDE Limewater is a saturated solution of calcium hydroxide in water. It is a clear colourless solution, which turns milky when carbon dioxide is passed through it for a few seconds. 5.5 Chemical changes involving calcium carbonate

53 CalciumhydroxideCalciumhydroxide CarbondioxideCarbondioxide CalciumcarbonateCalciumcarbonate (colourless solution) (white solid) Carbon dioxide is a colourless gas. It turns limewater milky Chemical changes involving calcium carbonate

Chemical changes involving calcium carbonate Figure 5.34 Carbon dioxide turns limewater milky. (a)(b) limewater (colourless solution) limewater turned milky

55 Figure 5.35 How some chemical changes involving calcium carbonate are related. Calciumcarbonate limestone strong heat Calcium hydroxide solution limewater add more water, stir well and then filter add a little water pass in carbon dioxide (limewater test) Calcium oxide quicklime carbon dioxide given off step1 step2 step4 step3 5.5 Chemical changes involving calcium carbonate Calciumhydroxide slaked lime

56 Q5.1 Write word equations for steps in 5.5 Chemical changes involving calcium carbonate Figure 5.35.

57 A5.1 Step 1: calcium carbonatecalcium oxide + carbon dioxide heat Step 2: calcium oxide + watercalcium hydroxide Step 3: calcium hydroxide + water calcium hydroxide solution (limewater) Step 4: calcium hydroxide solution (limewater) + carbon dioxide calcium carbonate + water 5.5 Chemical changes involving calcium carbonate

58 5.6TESTS FOR CALCIUM CARBONATE IN A SAMPLE OF LIMESTONE/CHALK/MARBLE TEST FOR CALCIUM IONS Figure 5.36 Calcium compounds give off a brick red flame in the flame test. 5.6 Tests for calcium carbonate in a sample of limestone/ chalk/marble

59 TEST FOR CARBONATE IONS Figure 5.37 Test for a carbonate by limewater test. Delivery tube 2. Carbon dioxide 2. Carbon dioxide turns limewater milky 1. Add dilute hydrochloric acid 5.6 Tests for calcium carbonate in a sample of limestone/ chalk/marble Solid sample under test

60 Q5.2 Write a word equation for the reaction between chalk and dilute nitric acid. A5.2 calcium carbonate + nitric acid calcium nitrate + carbon dioxide + water 5.6 Tests for calcium carbonate in a sample of limestone/ chalk/marble

61 Summary 1.The Earth's crust is composed mainly of a layer of rocks about 5 to 70 km thick. 2.A rock is a solid mass of a mineral or a mixture of minerals. 3.A mineral is a naturally occurring solid with a definite crystalline structure and chemical composition. 4.There are three main types of rocks: sedimentary rocks, igneous rocks and metamorphic rocks. Summary Rocks and Minerals

62 5.An ore is a mineral from which a constituent (usually a metal) can be profitably extracted. Some common ores include bauxite, copper pyrite, haematite and galena. 6.Two examples of extracting metals from ores: (a)Iron can be extracted from iron ores by heating haematite with carbon: iron(III) oxide + carbon iron + carbon dioxide (b)Aluminium can be extracted from bauxite by electrolysis: aluminium oxide aluminium + oxygen electrolysis heat Summary Extraction of metals from their ores

63 7.As reserves of minerals are limited, we need to conserve them. 8.Limestone, chalk and marble are different natural forms of the same compound, calcium carbonate. 9.Minerals are very useful. An example is limestone. See p. 88 for some of its uses. 10.Weathering of rocks refers to the slow process (usually over thousands of years) in which exposed rocks are broken down into smaller pieces. Summary Weathering and Erosion

64 11.Erosion of rocks refers to the slow process in which weathered rock pieces are transported away by gravity, wind and water. 12.Rocks are weathered in two ways: *Physical weathering (e.g. by temperature changes, frost action, abrasion) *Chemical weathering (e.g. attack by acid, attack by oxygen in air) Summary

65 14.On strong heating, limestone (mainly calcium carbonate) releases carbon dioxide and is changed into calcium oxide (quicklime). heat calcium carbonate calcium oxide + carbon dioxide 15.When calcium oxide (quicklime) is treated with water, it turns into calcium hydroxide (slaked lime). Summary 13.Rainwater attacks rocks, especially those containing calcium carbonate: calcium carbonate + carbonic acid calcium hydrogencarbonate Chemical changes involving calcium carbonate

66 16.Limewater is a saturated solution of calcium hydroxide in water. It is a colourless solution, which turns milky when carbon dioxide is passed through it for a few seconds. This limewater test can test for carbon dioxide gas. calcium hydroxide + carbon dioxide calcium carbonate + water (colourless solution) (white solid) 17.Calcium compounds give a brick red colour in the flame test. Summary Test for the presence of calcium and carbonate

67 18.On treatment with dilute hydrochloric acid, calcium carbonate dissolves and releases carbon dioxide. calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water Summary

68 Concept map Crust Rocks broken down into small pieces transported away by gravity, wind and water __________ rocks __________ rocks Igneous rocks contains Complete the following concept maps. MINERALS SedimentaryMetamorphic Ores ErosionWeathering

69 HaematiteBauxite heating with carbon examples ________ Concept map IronAluminium electrolysis

70 Rocks containing ___________ Marble Calcium carbonate _________ flame colour Carbonate ions Calcium oxide (_________) _________ (slaked lime) flame testadd hydrochloric acid add carbon dioxide strong heating add water Concept map calcite LimestoneChalk quicklime Brick red Carbon dioxide Calcium hydroxide Calcium ions

71 ENDEND Chapter 5 Rocks and minerals

72 BACK TO Q5.1 BACK TO Q5.1 Figure 5.35 How some chemical changes involving calcium carbonate are related. Calciumcarbonate limestone strong heat Calcium hydroxide solution limewater add more water, stir well and then filter add a little water pass in carbon dioxide (limewater test) Calcium oxide quicklimecarbon dioxide given off step1 step2 step4 step3 Calciumhydroxide slaked lime