2. 4.1 Rocks Rocks containing calcite (CaCO 3 ) (CaCO 3 ) limestone

3. 4.1 Rocks chalk

4. 4.1 Rocks marble

5. 4.1 Rocks P. 4 / 12 (limestone)(chalk) (marble) Calcite CaCO 3 contains Formed by skeletons and shells of sea animals sank to the bottom of the sea, covered by mud under heat and pressure for millions of years

6. 4.1 Rocks Limestone It is the most common form of calcium carbonate. It is hard and strong, yet inexpensive. It is widely used in the building industry.

7. 4.1 Rocks P. 6 / 12 Fig. 4.9 Spectacular limestone pinnacles rise along both sides of the Li River in Guilin, China.

8. 4.1 Rocks P. 7 / 12 Uses of limestone 1. To make footpath.

9. 4.1 Rocks P. 8 / 12 2. A raw material for making cement.

10. 4.1 Rocks P. 9 / 12 Chalk Fig. 4.10 Chalk cliffs in Sussex, England. Chalk is slightly softer and is also used in buildings.

11. 4.1 Rocks P. 10 / 12 Marble Marble is a crystalline solid and is very hard. It can be smoothly polished to give a beautiful appearance. It is often used for building statues, monuments, and as floors and walls in some buildings.

12. 4.1 Rocks P. 11 / 12 (limestone)(chalk) (marble)

13. 4.1 Rocks P. 12 / 17 Weathering and erosion Fig. 4.15 The Great Wall of China has been continuously weathered during the past 2200 years. All rocks exposed on the Earth’s surface are slowly worn away by weathering and erosion.

14. 4.1 Rocks P. 13 / 17 Fig. 4.16(a) Wind erosion caused this unusual limestone formation.

15. 4.1 Rocks P. 14 / 17 Fig. 4.16(b) A sea cliff in Hong Kong — a result of water erosion.

16. 4.1 Rocks P. 15 / 17 Types of weathering Rocks can be weathered in two ways: Physical weathering Chemical weathering

17. 4.1 Rocks P. 16 / 17 Rocks break! 2. Rocks cool down quickly at night 1. Rocks get hot in the daytime Physical weathering

18. 4.1 Rocks P. 17 / 17 Fig. 4.17 Rocks in deserts are badly weathered, partly due to big day- and-night temperature change.

19. 4.1 Rocks Chemical weathering CaCO 3 (s) + H 2 CO 3  Ca(HCO 3 ) 2 (aq) CO 2 + H 2 O  H 2 CO 3 Carbon dioxide in air dissolves slightly in rainwater, forming an acidic solution: The carbonic acid formed reacts with calcium carbonate: Attack by acid Calcium hydrogencarbonate is soluble in water and thus the limestone is slowly worn away. (acidic)‏

20. 4.1 Rocks P. 19 / 2 Earth’s crust Rocks containing ________ Marble calcite broken down into small pieces transported away by gravity, wind and water WeatheringErosion LimestoneChalk Physical Chemical Attacked by carbonic acid

21. 4.1 Rocks Thermal decomposition of calcium carbonate CaCO 3 gently warmed No visible change CaO CO 2 heated strongly

22. 4.1 Rocks calcium carbonate roaring non- luminous flame Bunsen burner test tube holder Fig. 4.23 Heating calcium carbonate strongly to make quicklime (calcium oxide).

23. 4.1 Rocks P. 22 / 8 H 2 O heat CaO (s) (quicklime) Ca(OH) 2 (S) (slaked lime)

24. 4.1 Rocks water Ca(OH) 2 (S) (slaked lime) Limewater Ca(OH) 2 (aq) filtered white suspension

25. 4.1 Rocks Limewater test for carbon dioxide limewater (colourless solution) Limewater is a saturated solution of calcium hydroxide in water. It is a clear colourless solution.

26. 4.1 Rocks When carbon dioxide is passed through limewater for a few seconds… limewater turned milky

27. 4.1 Rocks P. 26 / 8 Carbon dioxide Calcium hydroxide (colourless solution) water Carbon dioxide is a colourless gas. It turns limewater milky. (white solid) Calcium carbonate

28. 4.1 Rocks P. 27 / 8 Carbon dioxide Calcium hydrogencarbonate (colourless solution) water (white solid) Calcium carbonate

29. 4.1 Rocks Some chemical changes involving calcium carbonate are related. CaCO 3 Ca(OH) 2 (aq) CaO Ca(OH) 2 (s) pass in CO 2 (limewater test) ‏ add more H 2 O, stir well and then filter strong heat add a little H2O step 1 step 2 step 3 step 4 (limewater) (limestone) (slaked lime) (quicklime) CO 2 given off

30. 4.1 Rocks How can we show that limestone, chalk and marble all contain calcium ions and carbonate ions? ??

31. 4.1 Rocks P. 30 / 5 Test for calcium ions Calcium compounds give a brick-red flame in a flame test.

32. 4.1 Rocks Test for carbonate ions Fig. 4.27 Test for a carbonate ions by limewater test. dilute hydrochloric acid solid sample under test limewater delivery tube

33. 4.1 Rocks P. 32 / 5 hydrochloric acid Calcium carbonate Calcium chloride Carbon dioxide water

34. 4.1 Rocks Limestone, chalk and marble all give a positive limewater test.

35. 4.1 Rocks P. 34 / 2 Calcium carbonate Carbonate ions ________ flame colour Brick-red flame test add hydrochloric acid Carbon dioxide Calcium ions

36. 4.1 Rocks Some chemical changes involving calcium carbonate are related. CaCO 3 Ca(OH) 2 (aq) CaO Ca(OH) 2 (s) pass in CO 2 (limewater test) ‏ add more H 2 O, stir well and then filter strong heat add a little H2Or step 1 step 2 step 3 step 4 (limewater) (limestone) (slaked lime) (quicklime) CO 2 given off

37. 4.1 Rocks P. 36 / 2 Earth’s crust Rocks containing ________ Marble calcite broken down into small pieces transported away by gravity, wind and water WeatheringErosion LimestoneChalk Physical Chemical Attacked by carbonic acid

38. 4.1 Rocks P. 37 / 2 Calcium carbonate Carbonate ions ________ flame colour Brick-red flame test add hydrochloric acid Carbon dioxide Calcium ions