iGCSE chemistry Section 2 lesson 2

1. iGCSE chemistrySection 2 lesson 2

2. Content The iGCSE Chemistry course Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3 Organic Chemistry Section 4 Physical Chemistry Section 5 Chemistry in Society

3. Content Section 2 Chemistry of the Elements • The Periodic Table • Group 1 Elements • Group 7 Elements • Oxygen and Oxides • Hydrogen and Water • Reactivity Series • Tests for ions and gases

4. Content c) Group 7 elements — chlorine, bromine and iodine 2.9 recall the colours and physical states of the elements at room temperature 2.10 make predictions about the properties of other halogens in this group 2.11 understand the difference between hydrogen chloride gas and hydrochloric acid 2.12 explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in methylbenzene 2.13 describe the relative reactivities of the elements in Group 7 2.14 describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts 2.15 understand these displacement reactions as redox reactions. d) Oxygen and oxides 2.16 recall the gases present in air and their approximate percentage by volume 2.17 explain how experiments involving the reactions of elements such as copper, iron and phosphorus with air can be used to investigate the percentage by volume of oxygen in air 2.18 describe the laboratory preparation of oxygen from hydrogen peroxide,using manganese(IV) oxide as a catalyst 2.19 describe the reactions of magnesium, carbon and sulfur with oxygen in air, and the acid-base character of the oxides produced 2.20 describe the laboratory preparation of carbon dioxide from calcium carbonate and dilute hydrochloric acid 2.21 describe the formation of carbon dioxide from the thermal decomposition of metal carbonates such as copper(II) carbonate 2.22 describe the properties of carbon dioxide, limited to its solubility and density 2.23 explain the use of carbon dioxide in carbonating drinks and in fire extinguishers, in terms of its solubility and density 2.24 understand that carbon dioxide is a greenhouse gas and may contribute to climate change. • Lesson 2 • Group 7 elements • Oxygen and oxides

5. Group 7 elements – chlorine, bromine and iodine The HALOGENS

6. Group 7 elements – chlorine, bromine and iodine The HALOGENS All have seven electrons in their outer shell. To become stable they gain an electron and carry a charge of -1. eg. Br- I- Cl-

7. Group 7 elements – chlorine, bromine and iodine The HALOGENS Five non-metals

8. Group 7 elements – chlorine, bromine and iodine The HALOGENS Five non-metals Low melting and boiling points, increasing going down the group

9. Group 7 elements – chlorine, bromine and iodine Gas All have coloured vapours. Chlorine and bromine are extremely pungent (causing a sharp or irritating sensation) Gas Liquid Solid Solid

10. Group 7 elements – chlorine, bromine and iodine The HALOGENS are diatomic – this means that they go around as paired atoms.

11. Group 7 elements – chlorine, bromine and iodine The HALOGENS are diatomic – this means that they go around as paired atoms. Cl2 Br2

12. Group 7 elements – chlorine, bromine and iodine The HALOGENS are diatomic – this means that they go around as paired atoms. Cl2 Brittle and crumbly when solid. Br2

13. Group 7 elements – chlorine, bromine and iodine Poor conductors of heat and electricity, even when solid or liquid.

14. Group 7 elements – chlorine, bromine and iodine Going down the group, the halogens become less reactive. Poor conductors of heat and electricity, even when solid or liquid.

15. Group 7 elements – chlorine, bromine and iodine Halogens react with other non-metallic elements, such as hydrogen, to form molecular compounds: Eg. hydrogen + chlorine  hydrogen chloride H2(g) + Cl2(g)  2HCl(g)

16. What’s the difference between hydrogen chloride and hydrochloric acid (they both have the same chemical formula – HCl)

17. What’s the difference between hydrogen chloride and hydrochloric acid (they both have the same chemical formula – HCl) Hydrogen chloride is gaseous at room temperature. Hydrochloric acid is an aqueous solution of hydrogen chloride – i.e. dissolved in water.

18. Explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in methylbenzene

19. Explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in methylbenzene ?

20. Explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in methylbenzene ? “To separate, or split, into smaller particles or ions”

21. Hydrogen chloride?

22. Hydrogen chloride? Hydrogen chloride is a covalent compound. However, when dissolved in water it dissociates to the separate ions, H+ and CL-. The H+ ion gives it acidic properties.

23. Hydrogen chloride? When dissolved in an organic solvent, such as methylbenzene, hydrogen chloride does not dissociate into separate ions, so does not show acidic properties.

24. Hydrogen chloride? When dissolved in an organic solvent, such as methylbenzene, hydrogen chloride does not dissociate into separate ions, so does not show acidic properties.

25. Reactions of the halogens Halogens react with metals to produce ionic salts The halogen atom gains one electron to form the halide ion which carries a charge of -1 eg. Lithium + chlorine  lithium chloride 2Li(s) + Cl2(g)  2LiCl(s)

26. Reactions of the halogens Halogens react with metals to produce ionic salts The halogen atom gains one electron to form the halide ion which carries a charge of -1 eg. Lithium + chlorine  lithium chloride 2Li(s) + Cl2(g)  2LiCl(s) YouTube video: comparing the four halogens

27. Reactions of the halogens Summary: Halogens + Hydrogen  hydrogen halides HF, HCl, HBr, HI All four are gases and very soluble in water Halogens + Aluminium  Aluminium trihalides AlF3, AlCl3, AlBr3, AlI3 All four are white solids

28. Describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts

29. Describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts ?

30. Describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts “In a displacement reaction a more reactive element will displace a less reactive element from a compound.” ?

31. Halogen displacement reactions Remember that the reactivity of the halogens decreases as we go down the group, so Fluorine is the most reactive halogen, and Astatine is the least reactive – can you explain this trend in terms of the number of electron shells? (hint – think back to the Alkali metals)

32. Halogen displacement reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt. e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2

33. Halogen displacement reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt. e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 Cl2 KI solution Displaced iodine

34. Halogen displacement reactions A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt. e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 Cl2 KI solution Displaced iodine

35. Understand these displacement reactions as redox reactions

36. Understand these displacement reactions as redox reactions ?

37. Understand these displacement reactions as redox reactions “A redox reaction is where both oxidation and reduction occur.” ?

38. Redox reaction?

39. Hydrogen chloride? The loss of electrons from an atom is known as oxidation. The gain of electrons is known as reduction.

40. Hydrogen chloride? Remember OILRIG Oxidation Is Loss = OIL Reduction Is Gain = RIG

41. Hydrogen chloride? Remember OILRIG Oxidation Is Loss = OIL Reduction Is Gain = RIG

42. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl-

43. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- iodine loses 2e- (2I-  I2)

44. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- iodine loses 2e- (2I-  I2)

45. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- iodine loses 2e- (2I-  I2) iodine has been oxidised

46. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- chlorine gains 2e- (Cl2  2Cl-)

47. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- chlorine gains 2e- (Cl2  2Cl-)

48. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- chlorine gains 2e- (Cl2  2Cl-) chlorine has been reduced

49. Halogen displacement reactions e.g. potassium iodide + chlorine  potassium chloride + iodine 2KI + Cl2  2KCl + I2 2K+ 2I- 2K+ 2Cl- chlorine gains 2e- (Cl2  2Cl-) chlorine has been reduced In a REDOX reaction there is simultaneous oxidation and reduction. In this reaction, iodine has been oxidised, chlorine has been reduced.

50. Content c) Group 7 elements — chlorine, bromine and iodine 2.9 recall the colours and physical states of the elements at room temperature 2.10 make predictions about the properties of other halogens in this group 2.11 understand the difference between hydrogen chloride gas and hydrochloric acid 2.12 explain, in terms of dissociation, why hydrogen chloride is acidic in water but not in methylbenzene 2.13 describe the relative reactivities of the elements in Group 7 2.14 describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts 2.15 understand these displacement reactions as redox reactions. d) Oxygen and oxides 2.16 recall the gases present in air and their approximate percentage by volume 2.17 explain how experiments involving the reactions of elements such as copper, iron and phosphorus with air can be used to investigate the percentage by volume of oxygen in air 2.18 describe the laboratory preparation of oxygen from hydrogen peroxide,using manganese(IV) oxide as a catalyst 2.19 describe the reactions of magnesium, carbon and sulfur with oxygen in air, and the acid-base character of the oxides produced 2.20 describe the laboratory preparation of carbon dioxide from calcium carbonate and dilute hydrochloric acid 2.21 describe the formation of carbon dioxide from the thermal decomposition of metal carbonates such as copper(II) carbonate 2.22 describe the properties of carbon dioxide, limited to its solubility and density 2.23 explain the use of carbon dioxide in carbonating drinks and in fire extinguishers, in terms of its solubility and density 2.24 understand that carbon dioxide is a greenhouse gas and may contribute to climate change. • Lesson 2 • Group 7 elements • Oxygen and oxides