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3/17/2018 Carbon Chemistry OCR Gateway W Richards
Compounds are formed when two or more elements are chemically combined. Some examples: Methane Sodium chloride (salt) Glucose
Some simple compounds… Methane, CH 4 Water, H 2 O Carbon dioxide, CO 2 Key Hydrogen Ethyne, C 2 H 2 Oxygen Sulphuric acid, H 2 SO 4 Carbon Sulphur
More simple compounds… Water SO 2 Carbon dioxide H 2 O Carbon monoxide Na. HCO 3 Sodium hydrogencarbonate Na 2 CO 3 Sulfur dioxide CO 2 Sodium carbonate CO
Chemical formulae The chemical formulae of a molecule or compound is simply a way of showing the ratio of atoms in it. For example… Na Cl = sodium chloride (Na. Cl) K I = potassium iodide (KI) O K N O O = potassium nitrate (KNO 3)
Chemical formulae Try drawing these: 1) Water H 2 O 2) Carbon dioxide CO 2 3) Calcium sulphate Ca. SO 4 4) Magnesium hydroxide Mg(OH)2
Simple chemical reactions H Mg O Cl H Cl Cl + H Cl Water Mg. Cl 2 2 HCl + + H 2 O O O Mg Cu O S O Cu Mg Mg + Copper sulphate Cu. SO 4 O S O O Magnesium + O H Magnesium chloride Magnesium + Hydrochloric oxide acid Mg. O Mg Copper + Magnesium sulphate Cu + Mg. SO 4 O
Naming compounds Rule 1– If two identical elements combine then the name doesn’t change This happens with the following elements: 1) H 2 4) F 2 2) N 2 5) Cl 2 3) O 2 6) Br 2 These elements always go around in pairs (diatomic molecules). For example, hydrogen looks like this:
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 1) Sodium + chlorine 6) KBr 2) Magnesium + fluorine 7) Li. Cl 3) Lithium + iodine 8) Ca. O 4) Chlorine + copper 9) Mg. S 5) Oxygen + iron 10) 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 1) Potassium + hydrogen + oxygen 2) Lithium + hydrogen + oxygen 3) Calcium + hydrogen + oxygen 4) 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 1) Calcium + carbon + oxygen 6) Ag. NO 3 2) Potassium + carbon + oxygen 7) H 2 SO 4 3) Calcium + sulphur + oxygen 8) K 2 CO 3 4) Magnesium + chlorine + oxygen 5) Calcium + oxygen + nitrogen
Balancing equations 3/17/2018 Consider the following reaction: Sodium + water Na + sodium hydroxide + hydrogen Na O H H O H + 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”) H
Balancing equations 3/17/2018 We need to balance the equation: Sodium + water sodium hydroxide + hydrogen Na O H Na + Na H O O H Na H O H + H H Now the equation is balanced, and we can write it as: 2 Na(s) + 2 H 2 O(l) 2 Na. OH(aq) + H 2(g) H
Some examples 2 Mg O 2 2 Mg. O Zn + 2 HCl Zn. Cl 2 2 Fe + 3 Cl 2 2 Fe. Cl 3 Na. OH CH 4 Ca + 3/17/2018 + HCl + 2 O 2 Na. Cl CO 2 + + H 2 O + 2 H 2 O + 2 H 2 O Ca(OH)2 + + H 2 SO 4 Na 2 SO 4 + 2 H 2 O 2 CH 3 OH + 3 O 2 2 Na. OH 2 CO 2 + 4 H 2 O H 2
The structure of the atom 3/17/2018 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 NEUTRON – neutral, same mass as proton (“ 1”) PROTON – positive, same mass as neutron (“ 1”) ELECTRON – negative, mass nearly nothing
Mass and atomic number 3/17/2018 Particle Relative Mass Relative Charge Proton 1 +1 Neutron 1 0 Electron Very small -1 MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON NUMBER = number of protons (obviously)
Mass and atomic number 3/17/2018 How many protons, neutrons and electrons?
Atoms, ions and molecules An “atom” is simply one particle on its own in its “normal” state, e. g. a helium atom: An “ion” is an atom that has lost or gained electrons, e. g. sodium: A “molecule” is a combination of atoms in a compound: + Na Na
Examples of ionic molecules Magnesium chloride: Mg 2+ Cl Cl Mg + - - Cl Cl Mg. Cl 2 Calcium oxide: Ca + 2+ O Ca 2 - O Ca. O
Bonding introduced 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? Cl 3/17/2018
Bonding Cl 3/17/2018 Here comes 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? Cl H Now we’re both really stable. We’ve formed a covalent bond. H
Bonding Here comes another friend, Sophie Sodium Cl Na 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 + Cl 3/17/2018 Na Now we’ve both got full outer shells and we’ve both gained a charge. We’re both called IONS and we’ve formed an IONIC bond.
C 1 a – Making Crude Oil useful
Fuels A “fuel” is something that can be burned to release heat and light energy. The main examples are: Coal, oil and gas are called “fossil fuels”. In other words, they were made from fossils.
Hydrocarbons and crude oil 3/17/2018 Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: C C H H H Ethane H H H C C H H Butane H Increasing length H Longer chains mean… 1. Less ability to flow 2. Less flammable 3. Less volatile 4. Higher boiling
Distillation revision 3/17/2018 This apparatus can be used to separate water and ethanol because they have different ______. The ______ will evaporate first, turn back into a _______ in the condenser and collect in the _______. The water remains in the round flask, as long as the _______ does not exceed water’s boiling point. This method can be used to separate crude oil. Words – temperature, boiling points, ethanol, beaker, liquid
Forces between molecules Weak force of interaction here Longer molecules = stronger force of attraction
Fractional distillation 3/17/2018 Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures due to the different intermolecular forces between each molecule: Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom
Crude Oil 3/17/2018
Using Crude Oil Benefits Drawbacks Getting oil from unstable countries? Cheap to extract Wide range of uses as fuel Used to make plastics 3/17/2018 Crude Oil It’s going to run out Burning fossil fuels causes pollution It takes millions of years to form
Cracking 3/17/2018 Shorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”: Butane Ethane For example, this bond can be “cracked” to give these: Ethene
Cracking Gaseous hydrocarbon Long chain hydrocarbon Heated catalyst 3/17/2018 Liquid hydrocarbon This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst Cracking is used to produce plastics such as polymers and polyethanes. The waste products from this reaction include carbon dioxide, sulfur dioxide and water vapour. There are three main environmental problems here: 1) Carbon dioxide causes the _____ effect 2) Sulfur dioxide causes _____ 3) Plastics are not _______
C 1 b – Using Carbon Fuels
Choosing a fuel Does it create pollution? How much energy does it release? Which fuel should you use? How much does it cost? Is it toxic? Is it easy to use, store and transport?
Burning Fuels – “Combustion” Lots of oxygen: H H H O C O H Methane + O O Oxygen C H O Carbon dioxide + O O H H Water What would a balanced symbol equation for this reaction look like?
Incomplete Combustion Incomplete combustion is when a fuel is burned without having a plentiful supply of oxygen, e. g. when the Bunsen’s air hole is closed: H Some oxygen: H O C H H O H H Methane Little oxygen: H H O C + H H Methane + H C O O O Oxygen Carbon monoxide + Balanced symbol equations? O O H H H O H + H Water H C Carbon O H O Oxygen O C H O Water H H
Incomplete Combustion As well as producing carbon monoxide, incomplete combustion can also produce soot: Little oxygen: H H O C H Methane + O Oxygen H C Carbon “Soot” + O O Water H H
C 1 c – Clean Air
The Earth’s Atmosphere 3/17/2018 For the last 200 million years the atmosphere has remained roughly the same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0. 03% CO 2 Carbon dioxide, water vapour Oxygen Nitrogen Noble gases
The Carbon Cycle 5. Burning fossil fuels also releases CO 2 in air 4. Animals release CO 2 through respiration 3/17/2018 2. Plants and algae release CO 2 through respiration 1. CO 2 is taken in by plants and algae for photosynthesis and turned into carbohydrates, fats and proteins 3. The carbon taken in by plants is then eaten by animals and the animals that eat them
3/17/2018 Evolution of the Earth’s Atmosphere Carbon dioxide 4 Billion years Methane Ammonia Oxygen Nitrogen Others Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0. 03% CO 2 3 Billion years 2 Billion years 1 Billion years Present day
3/17/2018 Evolution of the Earth’s Atmosphere Volcanic activity releases CO 2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans. 4 Billion years 3 Billion years Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life. 2 Billion years 1 Billion years Green plants evolve which take in CO 2 and give out oxygen. Carbon from CO 2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released. Present day
Population and Pollution The human population is growing Population exponentially, particularly in countries like China and India: Time This has a number of effects on the environment: Farming – less land available for crops Waste – more waste needs to be disposed of Bigger population means… Resources – more resources needed, e. g. deforestation Pollution – More phosphates, nitrates, CO 2 and SO 2
Pollution What causes pollution? Carbon monoxide is a poisonous gas formed by incomplete combustion. Sulfur dioxide causes acid rain that kills aquatic life and damages buildings and metals. It’s caused when fuels containing sulfur are burned. Oxides of nitrogen cause photochemical smog and acid rain, and are formed in internal combustion engines
Reducing Pollution from vehicles A number of suggestions: 1) Buy a new, smaller, cleaner car 2) Buy a “hybrid” car 3) Convert your car to run on biodiesel 4) Make sure your car has a catalytic converter: Carbon monoxide + oxygen 2 CO + 2 NO 5) Use the train or a bus! carbon dioxide N 2 + 2 CO 2
C 1 d – Making Polymers
Hydrocarbons revision 3/17/2018 Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: C C H H H Ethane H H H C C H H Butane H Increasing length H Longer chains mean… 1. Less ability to flow 2. Less flammable 3. Less volatile 4. Higher boiling
Alkanes 3/17/2018 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 COVALENT bonds, for example: H C C H H Ethane H H H C C H H H Butane Alkanes are fairly unreactive (but they do burn well). The general formula for an alkane is Cn. H 2 n+2
General Formulae for Alkanes 3/17/2018 Instead of circles, let’s use letters… H H C H H H Methane (n=1) H H H C C H H H Propane (n=3) C C H H Ethane (n=2) H H C H H H H C C H H Butane (n=4) General formula for alkanes = Cn. H 2 n+2 H
Alkenes 3/17/2018 Ethane Ethene Butane ALKENES ALKANES Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds (a bond that has two shared electrons). For example: Butene This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. Alkenes turn bromine water colourless.
Testing for alkenes Bromine water Oil Bromine goes colourless 3/17/2018 This is an “addition” reaction where the colour change is caused by the formation of a colourless dibromo compound.
General Formulae for Alkenes 3/17/2018 H H H C C H Ethene (n=2) H H C C C H H H Propene (n=3) Butene (n=4) General formula for alkenes = Cn. H 2 n H
Monomers and Polymers H H C C H H Ethene 3/17/2018 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 (this often requires high pressure and a catalyst) Step 2: Add the molecules together: This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION
Another way of drawing it… 3/17/2018 Instead of circles, let’s use letters… H H C C H Ethene H H C C C H H H C C H Ethene H H H Poly(e)thene General formula for addition polymerisation: n C C n e. g. H n CH 3 H CH 3 C C H H n
Some examples C C H n H H C H C H H H C C Cl H Ethene – polyethene n H n 3/17/2018 Vinylchloride – n Polyvinylchloride (PVC) Cl H C C H H C C Polypropene n H n CH CH 3 3 HPropene –
C 1 e – Designer Polymers
Uses of addition polymers 3/17/2018 Poly(ethene) Poly(propene) What properties would these polymers have? Poly(styrene) Poly(chloroethene), PVC
Structure of Plastics 1) Some plastics have ____ intermolecular forces between each molecule – these have __ melting points and can be ______ easily as the molecules _____ over each other. 2) Some plastics have _____ forces between each molecule. These have ____ melting points and are ____. Words – high, low, strong, weak, stretched, rigid, slide
Outdoor Clothing I love doing outdoor sports. I’d like to wear clothing that is tough but also lets my sweat out. What should I wear?
Nylon and Gore-Tex 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”)
Gore-Tex Gore-tex is a material made from nylon laminated with the polymer PTFE and its invention has been of great use in the world of outdoor sports. Here’s how it works: Outer fabric Gore-tex Inner fabric Sweat Basically, the holes in the material are too small for water drops to pass through but big enough for sweat vapour. On its own, the membrane is too fragile so it is combined with nylon.
Disposal of plastics 1) Landfill sites - most plastics do not _____ which means that landfill sites are quickly filled up. Research is being carried out on _____ plastics. 2) Burning – this releases carbon dioxide which causes the ____ effect, as well as other ____ gases. 3) _______ – the best option, but difficult because of the different types of plastic Words – recycling, greenhouse, decompose, biodegradable, poisonous
Biodegradable carrier bags 3/17/2018 This carrier bag has been made with flax fibre from industrial waste.
C 1 f – Cooking and Food Additives
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”
The Chemistry of Cooking Now consider a potato cell: Cooking a potato causes the cell wall to break, leading to a softer texture. Starch grains also swell up and spread out.
Artificial Additives Why do we use additives? Some examples: Additive Interesting information Flavour enhancers Can include traditional ingredients like salt, vinegar etc. Monosodium glutamate is often used in Chinese foods (its found in soy sauce) Colour enhancers Processing food often results in colour loss so colour enhancers are used. Could be natural like carotenes or artificial like tartrazine Preservatives Can include vinegar and sugar. Artificial preservatives are used to stop microbes growing and antioxidants stop fats going off Vitamins and minerals Can be used to replace those lost during cooking
E numbers If artificial additives are “approved” they are given an E number: E 100–E 199 (colours) E 200–E 299 (preservatives) E 300–E 399 (antioxidants, acidity regulators) E 400–E 499 (thickeners, stabilizers, emulsifiers) E 500–E 599 (acidity regulators, anti-caking agents) E 600–E 699 (flavour enhancers) E 900–E 999 (miscellaneous) E 1000–E 1999 (additional chemicals)
Emulsions 3/17/2018 What’s an emulsion? It’s a mixture of oil and water, like in salad dressing… Paint is an emulsion. Other examples: Milk Cream Butterfat Watery liquid Butter
Why use emulsions? 3/17/2018 Emulsions can have varying textures and this makes them useful. Some examples: Different thicknesses of cream Paint and mayonnaise
Emulsifiers 3/17/2018 An emulsifier is an additive that will stop oil and water from seperating, like in mayonnaise. How they work: I don’t want to mix with you! Water I’m an emulsifier – I’ll sort this out with my hydrophobic end and my hydrophilic end! Oil The water and oil drops become “coated” and insulated from one another, which prevents them from seperating.
Uses of emulsifiers in food 3/17/2018 Emulsifiers are used: 1) In bread, to stop large _____ developing when it bakes 2) In low fat spreads, to allow the oil and water to be _____ 3) In ice cream and spray cream, to ______ the foam 4) In sponge cakes, to make tiny pockets of ____ 5) In chocolate, to stop melted chocolate forming _______ Words – crystals, air, holes, mixed, stabilise
Baking Powder Baking powder is used to make bread rise: Sodium hydrogen carbonate 2 Na. HCO 3(s) sodium carbonate + water + carbon dioxide Na 2 CO 3(s) + H 20(g) + CO 2(g) Gas Testing for carbon dioxide: Limewater turns milky/cloudy
C 1 g – Smells
Perfumes are synthetically made from chemicals called “esters”. Here are some facts about perfumes. Why are these things important? 1) Perfumes are non-toxic 2) They are non-irritants 3) They evaporate easily 4) They do not dissolve in water 5) They don’t react with water A typical perfume reaction: Ethanol + ethanoic acid C 2 H 5 OH + CH 3 COOH ethyl ethanoate + water C 2 H 5 OOCCH 3 + H 2 O
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
Solubility words Something that CAN dissolve is described as being… Solute How much of something that can be dissolved is called… Solution Something that CANNOT be dissolved is described as being… Solvent A solution that CAN’T dissolve anything else is… Soluble The solid that will be dissolved is the… Insoluble The mixture of solute and solvent is called the… The liquid that the solute will be dissolved into is the… Saturated Solubility
Making a solution A solution forms because there are: 1) Weak forces of attraction between solute molecules 2) 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. Esters can be used as solvents.
Cosmetics I think that the testing of cosmetics should be allowed. No way! I totally disagree. The testing of cosmetics on animals is currently banned in the EU. Who do you agree with and why?
C 1 h – Paints and Pigments
Paint is an example of a “colloid” – a mixture of one or more substances in a liquid but which are not dissolved. The molecules have a large surface area: volume ratio and, as such, they have a large surface tension and are difficult to separate. “Ingredients” in paint Function Solvent Gives the paint its colour Pigment Sticks the pigment to the surface Binding medium Thins the paint, making it easier to spread
Water based vs Oil based “Water-based paints” “Oil-based paints” In water-based paints the paint dries when the _______ evaporates, causing them to dry in around one ______. In oilbased paints the solvent has to ____ and then the oil is _______ by oxygen in the air, which takes longer and paint brushes have to be cleaned with ____ rather than water. Words – white spirit, evaporate, water, hour, oxidised
Thermochromic Paint Thermochromic paint is paint that changes colour when heated. Some uses: Acrylic paints can be added to thermochromic paint to give it an even wider range of colours. Here’s a strange use of this paint:
Phosphorescent Paint Phosphorescent paint is paint that contains pigments that can glow in the dark. They do this by “storing” energy and then release it over time: The original “glow-in-the-dark” paint contained radioactive materials so this paint is much safer!