True or False 20/04/2017 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

OCR Additional Science 20/04/2017 OCR Additional Science Chemicals of the Natural Environment

The Earth 1) The atmosphere 2) The hydrosphere 3) The biosphere 20/04/2017 1) The atmosphere 2) The hydrosphere 3) The biosphere 4) The lithosphere

The Carbon Cycle CO2 in air 20/04/2017 Respiration CO2 dissolves into the ocean CO2 in air Microbes respiring Photosynthesis Fossil fuels Respiration Carbon is eaten by animals Death of animals Death of plants Cement making Sediment pressurized

The Nitrogen Cycle N2 in air 20/04/2017 4. Denitrifying bacteria convert nitrates and ammonium compounds into atmospheric nitrogen N2 in air 1. Nitrogen-fixing bacteria convert N2 in the air into nitrates 1. Fertilisers Denitrifying bacteria Lightning Waste and dead animals 5. Nitrifying bacteria convert ammonium compounds into nitrates 6. Nitrates taken in by plants Nitrates in the soil 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

Chemicals in the Air Chemical Structure Diagram Boiling point/OC 20/04/2017 Chemical Structure Diagram Boiling point/OC Melting point/OC Oxygen, O2 O=O -183 -218 Nitrogen, N2 N=N -196 -210 Carbon dioxide, CO2 O=C=O -78 No liquid state Water vapour, H2O H-O-H 100 Argon. Ar Ar -186 -189

Forces 1) Forces between molecules: 20/04/2017 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 Each line represents an electron being shared between the atoms

Chemicals of the hydrosphere - Water 20/04/2017 e-

Dissolving a crystal lattice 20/04/2017 + - + - + - + - + -

Chemicals of the lithosphere - Silicon Dioxide 20/04/2017 Chemicals of the lithosphere - Silicon Dioxide 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 ________. Words – melting, covalent, insulator, hard, structure

Using Covalent Structures 20/04/2017 Element/ compound Property Uses Why? Carbon – diamond Very hard Drill tips Extremely strong covalent structure Silicon dioxide High melting point (1610OC) Furnace linings Very difficult to melt Silica glass Doesn’t conduct electricity Electrical insulators No free electrons to carry charge

Chemicals of the biosphere 20/04/2017 DNA Glucose

Sodium + water sodium hydroxide + hydrogen Balancing equations 20/04/2017 Consider the following reaction: Sodium + water sodium hydroxide + hydrogen Na O H O H Na + H + 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”)

Balancing equations We need to balance the equation: 20/04/2017 We need to balance the equation: Sodium + water sodium hydroxide + hydrogen Na O H O H Na O H Na O H + H + Na Now the equation is balanced, and we can write it as: 2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

Some examples 2 2 3 2 3 Mg + O2 Zn + HCl Fe + Cl2 NaOH + HCl CH4 + O2 20/04/2017 2 2 3 2 3 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 2 2 4

“Reduce” the oxygen to make iron Extracting Metals 20/04/2017 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: Oxide Iron Iron ore “Reduce” the oxygen to make iron

Increasing reactivity How do we do it? 20/04/2017 Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Copper Silver Gold Platinum Increasing reactivity 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” Carbon Oxide Iron 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

Calculating percentage mass 20/04/2017 Percentage mass (%) = Mass of element Ar Relative formula mass Mr x100% 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

Calculating the mass of metal 20/04/2017 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

Life Cycle Assessments (LCAs) 20/04/2017 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?

Solution containing copper and chloride ions Electrolysis 20/04/2017 ++++ ---- Positive electrode Negative electrode Cu2+ Cl- Solution containing copper and chloride ions Cu2+ Cl- Cu2+ Cl-

Electrolysis 20/04/2017 Electrolysis is used to separate a metal from its compound. = chloride ion = copper ion When we electrolysed copper chloride the _____ chloride ions moved to the ______ electrode and the ______ copper ions moved to the ______ electrode – OPPOSITES ATTRACT!!!

Electrolysis equations 20/04/2017 We need to be able to write “half equations” to show what happens during electrolysis (e.g. for copper chloride): At the negative electrode the positive ions GAIN electrons to become neutral copper ATOMS. The half equation is: Cu2+ + e- Cu 2 At the positive electrode the negative ions LOSE electrons to become neutral chlorine MOLECULES. The half equation is: Cl- - e- Cl2 2 2

Words – melting point, replaced, negative, bauxite, reactive, move Extracting Aluminium 20/04/2017 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

Electrolysis of Aluminium Oxide 20/04/2017 Overall: 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)

Using Iron 20/04/2017 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.

Copper, Aluminium and Titanium 20/04/2017 Metal Uses and why Extraction method Problems Copper Electrical wires – good conductor Electrolysis Limited supply Aluminium and titanium Planes – light and corrosion resistant Complicated and expensive Expensive and difficult to extract

Metals 20/04/2017 Metal atoms are very closely packed together in a regular arrangement. The atoms are held together by metallic bonds.

Properties of metals 20/04/2017 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

Words – slip, electrons, melting, electricity, strong, ions A closer look at metals 20/04/2017 + 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 + + + + + + + + + + +