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Carbon Chemistry

Carbon Chemistry. (OCR Gateway). W Richards The Weald School. The structure of the atom. ELECTRON – negative, mass nearly nothing. NEUTRON – neutral, same mass as proton (“1”). PROTON – positive, same mass as neutron (“1”).

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Carbon Chemistry

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  1. Carbon Chemistry (OCR Gateway) W Richards The Weald School

  2. The structure of the atom ELECTRON – negative, mass nearly nothing NEUTRON – neutral, same mass as proton (“1”) PROTON – positive, same mass as neutron (“1”) The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS: Dalton

  3. Mass and atomic number MASS NUMBER = number of protons + number of neutrons 4 He SYMBOL 2 PROTON NUMBER = number of protons (obviously)

  4. Elements These atoms are ALL iron – there’s nothing else in here If a solid, liquid or gas is made up of only one type of atom we say it is an element. For example, consider a tripod made up of iron:

  5. Compounds Sodium chloride (salt) Methane Glucose Compounds are different to elements. They contain different atoms. Here are some examples:

  6. Some simple compounds… Methane, CH4 Key Hydrogen Oxygen Carbon Sulphur Sulphuric acid, H2SO4 Carbon dioxide, CO2 Water, H2O Ethyne, C2H2

  7. An Introduction to Bonding 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?

  8. Bonding Cl H Cl H Here comes one of my friends, Harry Hydrogen Hey Johnny. I’ve only got one electron. Fancy sharing? Now we’re sharing electrons. We’ve formed a covalent bond.

  9. Bonding Cl + - Cl Na Na Here comes another friend, 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 I’ve given my electron to Jonny. This is an ionic bond.

  10. 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

  11. 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

  12. Chemical formulae • Try drawing these: • Water H2O • Carbon dioxide CO2 • Calcium sulphate CaSO4 • Magnesium hydroxide Mg(OH)2

  13. Naming compounds • This happens with the following elements: • H2 • N2 • O2 • F2 • Cl2 • Br2 These elements always go around in pairs (diatomic molecules). For example, hydrogen looks like this: Rule 1– If two identical elements combine then the name doesn’t change

  14. 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

  15. 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

  16. 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

  17. 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”)

  18. 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:

  19. 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

  20. Periodic Table Introduction

  21. Periodic table The periodic table arranges all the elements in groups according to their properties. Vertical columns are called GROUPS Mendeleev Horizontal rows are called PERIODS

  22. The Periodic Table Noble gases Alkali metals Halogens These elements are metals This line divides metals from non-metals These elements are non-metals

  23. The Chemistry of Cooking The process of cooking food causes some chemicals to turn into others (i.e. a chemical change) and these are irreversible. For example, consider a protein molecule: “Denatured”

  24. The Chemistry of Cooking Now consider a potato cell: Cooking a potato causes the cell wall to break and release starch grains

  25. Baking Powder Gas Sodium hydrogen carbonate sodium carbonate + water + carbon dioxide NaHCO3(s) Na2CO3(s) + H20(g) + CO2(g) Limewater Limewater turns milky/cloudy Baking powder is used to make bread rise: 2 Testing for carbon dioxide:

  26. Artificial Additives Why do we use additives? Some examples:

  27. E numbers If artificial additives are “approved” they are given an E number: E100–E199 (colours) E200–E299 (preservatives) E300–E399 (antioxidants, acidity regulators) E400–E499 (thickeners, stabilizers, emulsifiers) E500–E599 (acidity regulators, anti-caking agents) E600–E699 (flavour enhancers) E900–E999 (miscellaneous) E1000–E1999 (additional chemicals)

  28. Emulsions Butterfat Watery liquid Milk Cream Butter What’s an emulsion? It’s a mixture of oil and water, like in salad dressing… Paint is an emulsion. Other examples:

  29. Emulsifiers - the details Water Oil - + Emulsifier - - - - + -

  30. Active Packaging Active packaging is when a product is packaged with something that improves it, e.g. Silica gel, to absorb water A “widget”, to improve appearence and flavour

  31. Perfumes Ethanol + ethanoic acid ethyl ethanoate + water C2H5OH + CH3COOH C2H5OOCCH3 + H2O Here are some facts about perfumes. Why are these things important? • Perfumes are non-toxic • They are non-irritants • They evaporate easily • They do not dissolve in water • They don’t react with water A typical perfume reaction:

  32. Solutions revision If a substance CAN be dissolved it is called __________ If a substance CANNOT be dissolved it is called _________ Words – soluble, solute, solvent, solution, insoluble

  33. Making a solution • A solution forms because there are: • Weak forces of attraction between solute molecules • Strong forces of attraction between solute and solvent molecule For example, nail varnish remover works because the nail varnish remover molecules are attracted to the nail varnish molecules with a stronger attraction than water molecules are.

  34. Fuels Wood Oil Gas Coal These fuels are called “fossil fuels” and are described as being “non-renewable”. Fuels are substances that can be used to release useful amounts of energy when they burn, e.g.

  35. Crude Oil

  36. Hydrocarbons and crude oil H H C C H H H H Ethane Increasing length H H H H C C C C H H H H H H Butane Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: Longer chains mean… Less ability to flow Less flammable Less volatile Higher boiling point

  37. Fractional distillation Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:

  38. Forces between molecules Weak force of interaction here Longer molecules = stronger force of attraction

  39. Cracking Ethene Butane Ethane For example, this bond can be “cracked” to give these: Shorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:

  40. Cracking Gaseous hydrocarbon Long chain hydrocarbon Heated catalyst Liquid hydrocarbon This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst Cracking can be used (as well as fractional distillation) to extract petrol from crude oil.

  41. Alkanes H H C C H H H H Ethane H H H H C C C C H H H H H H Butane • Alkanes are SATURATED HYDROCARBONS. What does this mean? • HYDROCARBONS are molecules that are made up of hydrogen and carbon atoms • SATURATED means that all of these atoms are held together by single bonds, for example: Alkanes are fairly unreactive (but they do burn well).

  42. General Formulae for Alkanes H H H H H H H C C C C C C C H H H H H H H H H H H H H Methane (n=1) Ethane (n=2) H H H C C C H H H H H Propane (n=3) Butane (n=4) Instead of circles, let’s use letters… General formula for alkanes = CnH2n+2

  43. Alkenes ALKANES ALKENES Ethene Ethane Butane Butene Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example: This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE.

  44. General Formulae for Alkenes H H C C H H Ethene (n=2) H H H H H H H C C C C C C C H H H H H H H Propene (n=3) Butene (n=4) General formula for alkenes = CnH2n

  45. Monomers and Polymers H H C C H H Ethene This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics… Step 1: Break the double bond Step 2: Add the molecules together:

  46. Another way of drawing it… H H H H C C C C H H H H Ethene Ethene Poly(e)thene H H H H C C C C H H H H n C C n C C C C CH3 CH3 H H e.g. n C C n H H H H Instead of circles, let’s use letters… General formula for addition polymerisation:

  47. Some examples H H H H n C C n H H H H H H H H n C C n H H Cl Cl Cl Cl H H C C C C C C n C C n H H Br Br

  48. Uses of addition polymers Poly(ethene) Poly(propene) Poly(styrene) Poly(chloroethene), PVC

  49. Man made fibres Nylon – lightweight, tough, waterproof, blocks UV Gore-tex – nylon coated with PTFE – this means that it can allow perspiration to escape but rain cannot get in (it can “breathe”)

  50. Structure of Plastics 1) Some plastics have ____ intermolecular forces between each molecule – these have __ melting points and can be ________ easily 2) Some plastics have _____ forces between each molecule. These have ____ melting points and are ____. Words – high, low, strong, weak, stretched, rigid

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