Chemistry in Action W Richards The Weald School Edexcel module 4 27/11/2018 Chemistry in Action Edexcel module 4 W Richards The Weald School

Formation of oil and gas 27/11/2018 1) Layers of dead sea _____ settle on the seabed. 2) Layers of __________ rock build up on top. 3) The heat and ________ from these rocks, along with the absence of ______, mean that oil and gas are formed over ______ of years. Words – sedimentary, millions, oxygen, creatures, pressure

Hydrocarbons and crude oil 27/11/2018 Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples: Increasing length Longer chains mean… Less ability to flow Less flammable Less volatile Higher boiling point C H Ethane Butane C H

Fractional distillation 27/11/2018 Crude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures: Fractions with low boiling points condense at the top Fractions with high boiling points condense at the bottom

Fuels 27/11/2018 A “fuel” is something that can be burned to release heat and light energy. The main examples are: Although these fuels look different, they all contain CARBON and HYDROGEN – they’re called HYDROCARBONS

Burning Fuels Lots of oxygen: Some oxygen: Little oxygen: Methane 27/11/2018 C H O O H C O Lots of oxygen: Methane Oxygen + Carbon dioxide Water + Water + O H Methane C H Oxygen + O C O Some oxygen: Carbon monoxide O H Water + C H Methane Little oxygen: O Oxygen + C Carbon

Pollutants from burning fuels 27/11/2018 C O Carbon dioxide is a _______ gas and helps cause global _______. Carbon monoxide combines with ___________ in the _____ and reduces the ability for red blood cells to carry _______. Words – haemoglobin, warming, oxygen, greenhouse, blood C O

Alkanes Alkanes are SATURATED HYDROCARBONS. What does this mean? 27/11/2018 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 bonds, for example: Ethane Butane Alkanes are fairly unreactive (but they do burn well).

Alkenes ALKANES ALKENES 27/11/2018 Alkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example: Ethane Ethene ALKANES ALKENES Butane Butene This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. We can test for alkenes because they turn bromine water colourless.

For example, this bond can be “cracked” to give two of these: Cracking 27/11/2018 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 two of these: Ethane

Cracking Gaseous hydrocarbon Long chain hydrocarbon Heated catalyst 27/11/2018 Gaseous hydrocarbon Long chain hydrocarbon Heated catalyst 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, sulphur dioxide and water vapour. There are three main environmental problems here: Carbon dioxide causes the _________ effect Sulphur dioxide causes _____ _____ Plastics are not _____________

Monomers and Polymers 27/11/2018 Ethene 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: This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION

Another way of drawing it… 27/11/2018 Instead of circles, let’s use letters… Ethene C H H C Poly(e)thene General formula for addition polymerisation: C n C n e.g. C n H CH3 C n H CH3

Uses of addition polymers 27/11/2018 Poly(ethene) Poly(propene) Poly(styrene) Poly(chloroethene), PVC

Words – recycling, greenhouse, decompose, biodegradable, poisonous Disposal of plastics 27/11/2018 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

Enzymes In previous lessons we looked at enzymes and said: 27/11/2018 In previous lessons we looked at enzymes and said: Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. Enzymes work best in certain conditions: Enzymes are denatured beyond 40OC Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzyme activity Temp pH 400C

Uses of enzymes 27/11/2018 Daz 1) Enzymes are used in washing powders to help digest food stains. Biological washing powders will only work on 400C or lower. 2) Yeast is used to help a process called fermentation: Sugar Alcohol + carbon dioxide The alcohol from this process is used in making drinks and the carbon dioxide can be used to make bread rise. 3) Yoghurt making – an enzyme is used to convert lactose (a sugar found in milk) into lactic acid. 4) Cheese making – enzymes in rennet are used to make cheese

Universal Indicator and the pH scale 27/11/2018 Universal Indicator is a mixture of liquids that will produce a range of colours to show how strong the acid or alkali is: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Stomach acid Lemon juice Water Soap Baking powder Oven cleaner Strong alkali Strong acid Neutral An acid contains hydrogen ions, H+ An alkali contains hydroxide ions, OH-

Neutralisation reactions 27/11/2018 When acids and alkalis react together they will NEUTRALISE each other: OH Na Sodium hydroxide Cl H Hydrochloric acid The sodium replaces the hydrogen from HCl Cl Na Sodium chloride H2O Water

Neutralisation experiment 27/11/2018 In this experiment we mixed sodium hydroxide (an _____) and hydrochloric acid together and they ________ each other. The equation for this reaction is… Sodium hydroxide + hydrochloric acid sodium chloride + water A ____ was formed during the reaction, and we could have separated this by __________ the solution. The salt that we formed depended on the acid: Hydrochloric acid will make a CHLORIDE Nitric acid will make a _________ Sulphuric acid will make a _________ Words to use – nitrate, neutralised, alkali, sulphate, salt, evaporating

Making salts 27/11/2018 Whenever an acid and alkali neutralise each other we are left with a salt, like a chloride or a sulphate. Complete the following table: Hydrochloric acid Sulphuric acid Nitric acid Sodium hydroxide Sodium chloride + water Potassium hydroxide Potassium sulphate + water Calcium hydroxide Calcium nitrate + water

Production of Fertilisers 27/11/2018 Some salts made by neutralisation reactions can be used as fertilisers. For example: Ammonia + sulphuric acid ammonium ______ Ammonia + nitric acid ammonium ______

Limestone 27/11/2018 Limestone is a __________ rock made up of mainly calcium carbonate. It’s cheap and easy to obtain. Some uses: 1) Building materials – limestone can be quarried and cut into blocks to be used in _______. However, it is badly affected by ____ ____. 2) Glass making – glass is made by mixing limestone with _____ and soda: Limestone + sand + soda glass 3) Cement making – limestone can be “roasted” in a rotary kiln to produce dry cement. It’s then mixed with sand and gravel to make _______. Words – sand, building, sedimentary, concrete, acid rain

Limestone 27/11/2018 If soil is too _____ crops will fail. Limestone can also be used as a neutralising agent. There are two reactions to know: 1) Firstly, a THERMAL _________________ reaction is used to break the calcium carbonate down into calcium oxide (quicklime) and _______ __________: 2) This is then “slaked” with water to produce calcium hydroxide (“_________ lime”): Calcium hydroxide is alkaline and is used to ______ acidic soil. Calcium carbonate calcium oxide + carbon dioxide HEAT Calcium oxide calcium hydroxide WATER Words – slaked, acidic, neutralise, decomposition, carbon dioxide

Thermal decomposition 27/11/2018 Thermal Decomposition is when a substance breaks down into a simpler substance through the action of heat. For example, consider copper carbonate: Copper carbonate (green) turns into copper oxide (black) Limewater Limewater goes cloudy due to carbon dioxide being made Copper carbonate copper oxide + carbon dioxide

The “Limestone Cycle” CO2 Calcium Carbonate (limestone) CO2 27/11/2018 CO2 Calcium Carbonate (limestone) CO2 Step 4: add CO2 Step 1: heat Calcium Hydroxide solution (limewater) Calcium Oxide (lime or quicklime) Step 3: add more water and filter Step 2: add a little water H2O Calcium Hydroxide (slaked lime) H2O H2O H2O

Limewater: the reactions 27/11/2018 Step 1: Thermal decomposition Calcium carbonate calcium oxide + carbon dioxide CaCO3(s) CaO(s) + CO2(g) Step 2: Adding water Calcium oxide + water calcium hydroxide CaO(s) + H20(l) Ca(OH)2(aq) Step 3: Blowing into the limewater Calcium hydroxide + carbon dioxide calcium carbonate + water Ca(OH)2(aq) + CO2(g) CaCO3(s) + H20(l)