C2 Chemical Resources OCR Gateway Additional Science W Richards The Weald School
Chemical formulae Na Cl K I O O O The chemical formulae of a molecule or compound is simply a way of showing the ratio of atoms in it. For example… = sodium chloride (NaCl) = potassium iodide (KI) = potassium nitrate (KNO3) K N
Chemical formulae • Try drawing these: • Water H2O • Carbon dioxide CO2 • Calcium sulphate CaSO4 • Magnesium hydroxide Mg(OH)2
Naming compounds • This happens with the following elements: • H2 • N2 • O2 • F2 • Cl2 • Br2 Rule 1– If two identical elements combine then the name doesn’t change
Naming compounds Rule 2 – When two elements join and one is a halogen, oxygen or sulphur the name ends with ____ide e.g. Magnesium + oxygen magnesium oxide • Sodium + chlorine • Magnesium + fluorine • Lithium + iodine • Chlorine + copper • Oxygen + iron • KBr • LiCl • CaO • MgS • KF
Naming compounds Rule 3 – When three or more elements combine and two of them are hydrogen and oxygen the name ends with hydroxide e.g. Sodium + hydrogen + oxygen Sodium hydroxide • Potassium + hydrogen + oxygen • Lithium + hydrogen + oxygen • Calcium + hydrogen + oxygen • Mg(OH)2
Naming compounds Rule 4 – When three or more elements combine and one of them is oxygen the ending is _____ate e.g. Copper + sulphur + oxygen Copper sulphate • Calcium + carbon + oxygen • Potassium + carbon + oxygen • Calcium + sulphur + oxygen • Magnesium + chlorine + oxygen • Calcium + oxygen + nitrogen • AgNO3 • H2SO4 • K2CO3
Simple formulae to learn NaCl CaCl2 MgO HCl NaOH Ca(OH)2 CaCO3 HNO3 H2SO4 Mg(OH)2 Na2CO3 MgCl2 Sodium chloride Calcium chloride Magnesium oxide Hydrochloric acid Sodium hydroxide Calcium hydroxide Calcium carbonate Nitric acid Sulphuric acid Magnesium hydroxide Sodium carbonate Magnesium chloride H2O CO2 NH3 H2 O2 N2 K2SO4 Cl2 KCl CuO (NH4)2SO4 Water Carbon dioxide Ammonia Hydrogen Oxygen Nitrogen Potassium sulfate Chlorine Potassium chloride Copper oxide Ammonium sulfate
Simple chemical reactions O O O O O O O H Cl H Cl Mg Mg Cl H H Cl Mg Mg + Magnesium oxide + Hydrochloric acid Magnesium chloride Cu Cu + Mg MgO + + CuSO4 2HCl S S MgCl2 O O O + Magnesium + Copper sulphate Copper + Cu Water H2O Magnesium sulphate MgSO4 Notice that the number of atoms on each side of the equation is the same!
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”)
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:
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
Bonding Introduction Cl Cl Hi. My name’s Johnny Chlorine. I’m in Group 7, so I have 7 electrons in my outer shell I’d quite like to have a full outer shell. To do this I need to GAIN an electron. Who can help me?
Ionic Bonding 16/11/2014 Cl + - Cl Na Na Here comes my friend again, Sophie Sodium Hey Johnny. I’m in Group 1 so I have one electron in my outer shell. Unlike Harry, this electron is far away from the nucleus so I’m quite happy to get rid of it. Do you want it? Okay Now we’ve both got full outer shells and we’ve both gained a charge. We’ve formed an IONIC bond, which is basically caused by the attraction between our charges.
Covalent Bonding 16/11/2014 Cl H Cl H Here comes another one of my friends, Harry Hydrogen Hey Johnny. I’ve only got one electron but it’s really close to my nucleus so I don’t want to lose it. Fancy sharing? Now we’re both really stable. We’ve formed a covalent bond.
Balancing ions 16/11/2014 Some common ions: Sodium – Na+ Potassium – K+ Magnesium – Mg2+ Ammonium – NH4+ Chloride – Cl- Bromide – Br- Oxide – O2- Sulphate – SO42- • Determine the formula of the following compounds: • Sodium chloride • Magnesium oxide • Magnesium chloride • Ammonium chloride • Sodium sulphate • Sodium oxide
Atom, molecule or ion? Are the following things atoms, molecules or ions? • H2 • NH3 • Cl- • K2SO4 • Au • CO32- • Na • CO2 • H+ • H2O • Molecule • Molecule • Ion • Molecule • Atom • Ion • Atom • Molecule • Ion • Molecule
The Structure of the Earth A thin, relatively cold crust - 10-100km thick and not very dense A mantle – has the properties of a solid but the lower parts can also flow A core – made of molten nickel and iron. Outer part is liquid and inner part is solid Scientists have learnt this by studying seismic waves (earthquakes) as the crust is too think to drill through.
Movement of the Lithosphere These plates are moving apart from each other a few centimetres every _______ due to the ________ currents in the mantle caused by the ________ decay of rocks inside the core. The Earth’s LITHOSPHERE (i.e. the _______) is split up into different sections called ________ plates: Words – radioactive, crust, convection, tectonic, year
Plate Movements Earthquakes and volcanic eruptions can be common here Igneous Rock Oceanic Crust Mantle Convection Currents Magma
More on Plate Movements Subduction Convection Currents Thick, less dense continental plate Thin, dense oceanic plate
Tectonic Plate movements Look at the coastlines of South America and Africa. I wonder of they used to fit together… Alfred Wegener I’m going to call this my Theory of Continental Drift
Tectonic theory • What’s my evidence for this? Three things: • The “jigsaw fit” • Each continent has similar rocks and fossils • Each continent has similar animal species
Tectonic theory 16/11/2014 • The Evidence: • Some continents look like they used to “fit” together • Similar rock patterns and fossil records The Problems: Wegener couldn't explain how continental drift happened so nobody believed him • The Answer: • Scientists discovered 50 years later that the Earth generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move • We also now know that the sea floor is spreading outwards from plate boundaries Conclusion – scientists now believe Wegener’s Tectonic Theory
Another Example of Continental Drift This is where India is now This is where India was millions of years ago The formation of mountain ranges can be explained by tectonic theory. Consider the Himalayas at the top of India:
Magnetic Patterns in Sea Floor Spreading 16/11/2014 The Earth’s magnetic field swaps poles every million years. The above picture shows those changes recorded over time in rocks on the sea floor and provides evidence for long-term sea floor spreading.
Igneous Rock Granite – a slow cooling rock with big crystals and rich in silica Rhyolite – a fast cooling rock with small crystals and rich in silica Gabbro – a slow cooling rock with big crystals and rich in iron Basalt – a fast cooling rock with small crystals and rich in iron
Volcanoes Picture: EPA What do you think of the following photo? Geologists study volcanoes to get better at forecasting future ones and to reveal more information about the structure of the Earth.
Building Materials Bricks are made from clay Iron and aluminium come from ores. Glass is made from sand Many of our common building materials are found in the Earth:
Building Materials Limestone – a sedimentary rock so fairly soft Granite – an igneous rock and very hard Marble (made from chalk or limestone under high pressure and heat) and fairly hard Here are some common rocks used in buildings:
Limestone HEAT Calcium carbonate calcium oxide + carbon dioxide HEAT CaCO3 CaO + CO2 Limestone is a __________ rock made up of mainly calcium _______. It’s cheap and easy to obtain. Some facts: 1) Building materials – limestone can be quarried and cut into blocks to be used in buildings. However, it is badly affected by ____ ____. 2) Limestone ________ when heated to form calcium oxide and carbon dioxide: 3) Cement making – limestone can be “roasted” in a rotary kiln to produce dry cement. It’s then mixed with sand and aggregate to make _______. Words – concrete, acid rain, carbonate, sedimentary, decomposes
Pros and Cons of quarrying limestone 16/11/2014
Concrete Concrete is a strong building material and can be made even stronger with reinforcements: Reinforcing concrete is better than plain concrete because it is both stronger and the steel is more flexible.
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
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 Copper
Reducation and Oxidation heat Aluminium + iron oxide aluminium oxide + iron 2Al(s) + Fe2O3(s) Al2O3(s) + 2Fe(s) heat heat Magnesium + oxygen magnesium oxide Mg(s) + O2(s) 2MgO(s) heat OIL RIG Oxidation is Loss of Electrons Reduction is Gain of Electrons An example of reduction: An example of oxidation:
Purifying Copper ++++ ---- Impure copper Pure copper Cu2+ Cu2+ Cu2+ At the anode: Cu(s) Cu2+(aq) + 2e- At the cathode: Cu2+(aq) + 2e- Cu(s) Solution containing copper ions “Oxidation” “Reduction”
Recycling metals Reasons why recycling is good Reasons why recycling is bad Still requires energy Reduces demand for raw materials Recycling Requires money to sort and recycle Saves energy
Alloys Gold mixed with copper Aluminium mixed with magnesium and copper Aluminiun mixed with chromium Steel is an “alloy” – i.e. a mixture of metals. Here are other alloys:
Alloys and their uses Brass – copper and zinc Amalgam - mercury Solder – lead and tin Here are some common alloys and their main uses and metals:
Smart Alloys A “smart alloy” is one that can “remember” its original state after being bent or stretched. These glasses are made from a “smart” material – if they are bent they will return to their original shape
Gold alloys 24-Carat gold 9-Carat gold “Pure gold” – 99.99% of the atoms in this bar are gold atoms (fineness off 999.9). Pure and malleable but soft. “9 carat gold” – around 9/24ths of the atoms in these earrings are gold atoms. Harder than pure gold but less malleable. Gold can be mixed with other metals to make alloys with different properties. For example:
Materials in a Car Copper wires Glass windscreen Nylon seatbelts Alloy wheels Steel body Plastic trim
Rusting Tube 1 – drying agent Tube 2 – boiled water Tube 3 – water + air Tube 4 – water + air + salt Task: To investigate what causes rusting
Rusting Iron + oxygen + water hydrated iron oxide “Rusting” is the adding of oxygen to iron to form iron oxide (this is called “oxidation”) No rust No rust Rust Lots of rust Salt water and acid rain can also increase the rate of rusting.