True or False

1. True or False In a ‘reduction’ reaction Oxygen is added to a metal In electrolysis a positive ion is attracted to the positive electrode (anode) Organic chemicals found in the Biosphere are often formed around chains of CARBON atoms Photosynthesis adds carbon to the atmosphere Chemicals of the atmosphere have high boiling points and are made up of molecules containing lots of atoms Giant covalent structures such as Silicon Dioxide have high melting points

2. OCR Additional Science Chemicals of the Natural Environment

3. The Earth 1) The atmosphere 2) The hydrosphere 3) The biosphere 4) The lithosphere

4. The Carbon Cycle CO2 in air Respiration CO2 dissolves into the ocean Microbes respiring Photosynthesis Fossil fuels Respiration Carbon is eaten by animals Death of animals Death of plants Cement making Sediment pressurized

5. The Nitrogen Cycle N2 in air 1. Fertilisers Denitrifying bacteria Lightning Waste and dead animals Nitrates in the soil 4. Denitrifying bacteria convert nitrates and ammonium compounds into atmospheric nitrogen 1. Nitrogen-fixing bacteria convert N2 in the air into nitrates 5. Nitrifying bacteria convert ammonium compounds into nitrates 6. Nitrates taken in by plants 3. Decomposers break down waste products and dead animals and plants to form AMMONIUM COMPOUNDS 2. Plants are then eaten by animals – the nitrogen becomes PROTEIN

6. Chemicals in the Air

7. Forces Each line represents an electron being shared between the atoms 1) Forces between molecules: The forces between each molecule are very _____ so the molecules can _____ be pulled apart. 2) Forces within the molecule: Forces within the molecules are very ______ due to the _______ bond so its very difficult to pull apart each molecule

8. Chemicals of the hydrosphere - Water e- e- e- e-

9. Dissolving a crystal lattice + - + - + - + - + -

10. Chemicals of the lithosphere - Silicon Dioxide O Si O O O O Si Si O O O Silicon dioxide forms a giant ______ structure where each atom is covalently bonded, forming a very strong 3-D ______. This causes it to be _____, have high _____ and boiling points and a good electrical ________. O O Words – melting, covalent, insulator, hard, structure

11. Using Covalent Structures

12. Chemicals of the biosphere Glucose DNA

13. Balancing equations Sodium + water sodium hydroxide + hydrogen O Na Na H H H H H O Consider the following reaction: + + This equation doesn’t balance – there are 2 hydrogen atoms on the left hand side (the “reactants” and 3 on the right hand side (the “products”)

14. Balancing equations Sodium + water sodium hydroxide + hydrogen O O Na Na Na Na H H H H H H H H O O 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g) We need to balance the equation: + + Now the equation is balanced, and we can write it as:

15. Some examples Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2 Ca + H2O NaOH + H2SO4 CH3OH + O2 MgO ZnCl2 + H2 FeCl3 NaCl + H2O CO2 + H2O Ca(OH)2 + H2 Na2SO4 + H2O CO2 + H2O 2 2 2 3 2 2 2 2 3 2 2 2 2 2 4

16. Extracting Metals Oxide Iron Some definitions: A METAL ORE is a mineral or mixture of minerals from which it is “economically viable” to extract some metal. Most ores contain METAL OXIDES (e.g. rust = iron oxide). To “extract” a metal from a metal oxide we need to REDUCE the oxygen. This is called a REDUCTION reaction. To put it simply: Iron ore “Reduce” the oxygen to make iron

17. How do we do it? Metals ABOVE CARBON, because of their high reactivity, are extracted by ELECTROLYSIS Metals BELOW CARBON are extracted by heating them with carbon in a BLAST FURNACE. This is a “displacement reaction” Increasing reactivity These LOW REACTIVITY metals won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Copper Silver Gold Platinum Carbon Oxide Iron

18. Calculating percentage mass Mass of element Ar x100% Percentage mass (%) = Relative formula mass Mr Calculate the percentage mass of magnesium in magnesium oxide, MgO: Ar for magnesium = 24 Ar for oxygen = 16 Mr for magnesium oxide = 24 + 16 = 40 Therefore percentage mass = 24/40 x 100% = 60% Calculate the percentage mass of the following: • Hydrogen in hydrochloric acid, HCl • Potassium in potassium chloride, KCl • Calcium in calcium chloride, CaCl2 • Oxygen in water, H2O

19. Calculating the mass of metal After you’ve calculated the percentage mass you can work out the actual mass of a metal: Mass of metal = % mass of metal x mass of substance Calculate the mass of metal in the following: • Potassium in 10g of potassium chloride, KCl • Sodium in 20g of sodium chloride, NaCl • Calcium in 50g of calcium chloride, CaCl2 • Magnesium in 100g of magnesium chloride, MgCl2

20. Life Cycle Assessments (LCAs) Step 1: Manufacture What resources are needed? What effect will this have on the environment? Step 2: Use How much energy will be needed? What is the effect on the environment? Step 3: Disposal How is the product disposed of? What is the effect on the environment?

21. Electrolysis ++++ ---- Positive electrode Negative electrode Solution containing copper and chloride ions Cl- Cl- Cl- Cu2+ Cu2+ Cu2+

22. Electrolysis = chloride ion = copper ion Electrolysis is used to separate a metal from its compound. When we electrolysed copper chloride the _____ chloride ions moved to the ______ electrode and the ______ copper ions moved to the ______ electrode – OPPOSITES ATTRACT!!!

23. Electrolysis equations At the negative electrode the positive ions GAIN electrons to become neutral copper ATOMS. The half equation is: Cu2+ + e- Cu At the positive electrode the negative ions LOSE electrons to become neutral chlorine MOLECULES. The half equation is: Cl- - e- Cl2 We need to be able to write “half equations” to show what happens during electrolysis (e.g. for copper chloride): 2 2 2

24. Extracting Aluminium Aluminium has to be extracted from its ore (called ________) by electrolysis. This is because aluminium is very ___________. The ore is mixed with cryolite to lower its ________ ________. The ore is then melted so that the ions can ______. The positively charged aluminium ions gather at the ___________ electrode. Oxygen forms at the positive electrode and causes it to wear away, which means that they have to be __________ frequently. Words – melting point, replaced, negative, bauxite, reactive, move

25. Electrolysis of Aluminium Oxide Aluminium oxide aluminium + oxygen 2Al2O3(l) 4Al(l) + 3O2(g) At the cathode: At the anode: Al3+(l) + 3e- Al(l) 2O2-(l) - 4e- O2(g) Overall:

26. Using Iron Iron produced by the blast furnace (“cast iron”) contains about 96% iron and 4% impurities. These impurities make it very brittle and easy to break. Ironbridge, Shropshire – made out of cast iron and safe for horses and carts but not modern vehicles.

27. Copper, Aluminium and Titanium

28. Metals Metal atoms are very closely packed together in a regular arrangement. The atoms are held together by metallic bonds.

29. Properties of metals Metals have very high melting points (which means that they are usually _____) whereas non-metals will melt at lower ___________ All metals conduct heat and __________ very well, whereas non-metals don’t (usually) Metals are strong and ______ but bendable. Non-metals are usually _____ or they will snap. Metals will _____ when freshly cut or scratched, whereas non-metals are usually dull. Metals have higher _______ than non-metals (i.e. they weigh more) Metals can be used to make ______ (a mixture of different metals) Words - alloys, electricity, solids, weak, densities, temperatures, tough, shine

30. A closer look at metals + + + + + Metals are defined as elements that readily lose ______ to form positive ____. The ions are closely packed (hence the metal is ______) and they have strong bonds holding them together (hence the high _______ points). The presence of free electrons means that metals can conduct ______. Metals can bend because the layers can “____” over each other: + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Words – slip, electrons, melting, electricity, strong, ions + + + + + + + + + +