Yr 11 Masterclass! - Double. 1.Bonding 2.Acids 3. Metal extraction 4.Energy 5.Organics

Transcription

1 Yr 11 Masterclass! - Double 1.Bonding 2.Acids 3. Metal extraction 4.Energy 5.Organics

2 1 Metallic bonding Structure Properties Explanation Delocalised sea of electrons High boiling and melting points Conducts electricity/ Good thermal conductors Have to beak very strong electrostatic attractions between the metal ions and delocalised electrons. Delocalised electrons are free to move. Malleable and ductile Shiny, dense, hard, strong Metal ions are in layers which can slip over each other Regular, tightly packed arrangement of metal ions. H Metals with more electrons on their outer shells (higher groups) have higher melting and boiling points because they give more electrons to the sea and so their metal ions have a higher charge so greater electrostatic attraction to break.

3 Ionic Bonding Always a metal and a non metal!

4 What if the numbers don t match?

5 Ionic bonding Structure Properties Explanation Cannot conduct electricity when solid Can conduct electricity when molten or dissolved. Soluble in water. High melting and boiling points. Ions cannot move. Ions are free to move. The charged water molecules surround the ions, separating them from the lattice. Very strong electrostatic attractions to break so a lot of energy required H The more electrons lost and/or gained the stronger the electrostatic attraction so the higher the boiling points e.g Magnesium oxide (2 lost/2 gained) is higher than sodium chloride (1 lost one, 1 gained)

6 Covalent - Share a pair or two? Water Chlorine H H Oxygen Nitrogen

7 Simple molecular structures Structure Properties Explanation Does not conduct electricity. No free ions or electrons. Poor conductor of heat. Molecules are spread out. Low melting and boiling points (Gases at room temp) Low density/not shiny Have weak intermolecular forces so little energy is needed to break them. Random arrangement and spread out

8 Giant Covalent structures Graphite Diamond strong covalent bonds so.. Conducts electricity as free delocalised electrons. Hard Brittle Lubricant as layers can slip strong covalent bonds so.. Cannot conduct electricity no free charges. Very hard Not brittle -no layers Not a lubricant- no layers

9 Fullerenes 1. What are fullerenes? Cage structures made of carbon atoms 2. What is the name of the C60 ball? Buckminsterfullerene 3. What uses are there for buckyballs or nanotubes in medicine? Drug delivery to specific sites eg cancer drugs direct to tumor 4. How can they help in lubrication? Reduction of friction 5. What is a carbon nanotube? Layer of Graphene rolled into a tube 6. Why do nanotubes have potential for use with catalysts? Can help to increase the surface area of the catalyst 7. How big are nanotubes compared to a human hair fiber? 2000x smaller than carbon fibre (not to be confused with each other!) Approx. 4 nanometer diameter, twice a DNA strand 8. What are the properties of nanotubes/graphene? Strongest tested material, best electrical conductor free electrons, very low density. 9. What future uses do fullerenes have? Make flexible computer clothing, smaller more efficient fuel cells, lighter and stronger building materials etc

10 Nanotechnology Individual atoms do not have the same properties as bulk substances e.g. nanotubes, graphene vs diamond and graphite. Uses of silver nanoparticles antibacterial, antiviral, antifungal used in,antiseptic sprays, refrigerator linings, socks, deodorants etc Nano titanium dioxide Risks sun creams as transparent as absorb and reflect UV and self cleaning glass -cause water to spread out in a thin layer and catalyses the breakdown of dirt in the presence of UV current nanomaterials have been tested to check no damage to the environment or individuals long term effects are unknown. Concern that silver nanoparticles and titanium dioxide nanoparticles are applied to the skin so can be absorbed into the blood stream and get to the brain unknown damage need labels on product.

11 Smart materials These materials have properties that can change when a change occurs in their environment This change is reversible. Thermochromic pigments change colour with changing temperature Photochromic pigments change colour with changing light intensity Polymer gels e.g. hydrogels absorb/expel water and swell/shrink (up to 1000 times their volume) due to changes in ph or temperature Shape memory alloys regain original shape when heated Shape memory polymers regain original shape when heated

12 2 Acids An alkali is a soluble base! 1 Acid + Alkali salt + water H 2 SO 4 + 2NaOH Na 2 SO 4 + 2H 2 O 2 Acid + Base salt + water 2HNO 3 + CuO Cu(NO 3 ) 2 + H 2 O 3 Acid + Metal salt + hydrogen 2HCl + Mg MgCl 2 + H 2 4 Acid + Carbonate salt + water + Carbon dioxide Bubbles 2HCl + CaCO 3 CaCl 2 + H 2 O + CO 2

13 All metals above hydrogen will react with acids Metal + acid Squeaky pop with a lit spill metal salt + hydrogen Excess Metal/oxide/ Warm to Filter Evaporate Carbonate evaporate to 1/3 (Longer = bigger) Reactivity series Peter Potassium (K) Simon Sodium (Na) Caught Calcium (Ca) Mice Magnesium (Mg) And Aluminium (Al) Coloured Carbon Zebras Zinc (Zn) In Iron (Fe) The Tin (Sn) Loo, Lead (Pb) He Hydrogen couldn t Copper (Cu) Save Silver (Ag) golden Gold (Au) Platypus Platinum (Pt)

14 Neutralisation by titration. NaOH + HCl NaCl + H 2 O 1. Place acid/alkali in burette. 2. Take initial reading. 3. Pipette known volume of acid/alkali into flask on a white tile. 4. Add indicator to flask 5. Add acid/alkali from burette drop wise and swirl. 6. Stop when a permanent colour change and record final reading. 7. Repeat and calculate average. 8. Ensure readings are from the bottom of the meniscus. Acids all release H + ions in water. HCl H + + Cl - Alkalis all release OH - ions in water. KOH K + + OH - Neutralisation = H + + OH - H 2 O Exothermic Gives out heat! To get the salt Add the mean value of acid to the same volume of alkali without adding indicator and evaporate. If 20cm 3 of NaOH was in the flask and 30cm 3 of acid was added, the acid must be weaker.

15 Testing for sulfates Add barium chloride (or barium nitrate) White precipitate forms Salt all nitrates all salts of sodium & potassium silver chloride silver bromide silver iodide barium sulfate calcium carbonate hydroxides of metals not in Group 1 Solubility soluble soluble insoluble insoluble insoluble insoluble insoluble insoluble Equations: sodium + barium barium + sodium sulfate chloride sulfate chloride Na 2 SO 4 (aq) + BaCl 2 (aq) BaSO 4 (s) + 2NaCl(aq) SO 4 2- (aq) + Ba 2+ (aq) BaSO 4 (s) Ionic equation

16 3 Extracting metals 1 Competitive metals A more reactive metal will displace a less reactive metal. E.g. Thermite Fe 2 O 3 + 2Al 2 Fe + Al 2 O 3 2 Reduction -REDOX Any metal less reactive than carbon can be extracted using carbon 2CuO + C 2Cu + CO 2 Reduced Oxidised 3 Electrolysis Any metal more reactive than carbon is extracted using electrolysis Reactivity series Peter Potassium (K) Simon Sodium (Na) Caught Calcium (Ca) Mice Magnesium (Mg) And Aluminium (Al) Coloured Carbon Zebras Zinc (Zn) In Iron (Fe) The Tin (Sn) Loo, Lead (Pb) He Hydrogen couldn t Copper (Cu) Save Silver (Ag) golden Gold (Au) Platypus Platinum (Pt)

17 Blast Furnace carbon + oxygen carbon dioxide C(s) + O 2 (g) CO 2 (g) Carbon dioxide + carbon carbon monoxide CO 2 (g) + C(s) 2CO(g) Carbon monoxide + iron oxide iron + carbon dioxide 3CO(g) + Fe 2 O 3 (s) 2Fe(s) + 3CO 2 (g) Decomposition Calcium carbonate calcium oxide + carbon dioxide Neutralisation Continuous process (cost of getting up to temperature) CaCO 3 (s) CaO(s) + CO 2 (g) Calcium oxide + silicon dioxide calcium silicate CaO(s) + SiO 2 (s) CaSiO 3 (s) Slag! Iron ore = source of iron Coke = Fuel and to produce carbon monoxide Hot air = Supplies oxygen for coke to burn Limestone = remove impurities- sand

18 Facts Transition metals Found in the middle of the periodic table. Show properties of typical metals e.g. malleable Often used as catalysts e.g. platinum in catalytic convertors Can form more than one ion. Compounds are often coloured. Fe 2+ = pale green Fe 3+ = brown Cu 2+ = blue Aluminum Strong, low density, good conductor of heat and electricity, resistant to corrosion. - Planes/Electric wires between pylons Titanium Hard, Strong, low density, resistant to corrosion, high melting point. -Limb replacements Copper Very good conductor of heat and electricity, malleable, ductile, attractive colour and luster -Jewelry/ Electrical wiring Iron and steel Hard and strong. Construction bridges - Trains

19 of molten liquids Anode Molten liquid Cathode Electrolyte is molten so ions are free to move Cathode - all metals will form gaining electrons Cu e - Cu Cu 2+ cation is reduced Anode all non metals will form loosing electrons 2Cl - 2e - + Cl 2 Cl - anion is oxidised P ositive A node N egative I s C athode O xidation I nvolves L oss r eduction I nvolves g ain

20 Electrolysis of alumina aluminum oxide The oxygen produced reacts with the graphite anodes producing CO 2 so they have to be continually replaced. It is an expensive process as it requires a lot of energy. Cathode ---- Al 3+ reduced Al e - Al Anode ---- O 2- oxidised 2O 2- O 2 + 4e -

21 Factors affecting economic viability and sustainability of extraction processes. 1. Why are plants near the coasts? IMPORT raw materials 2. What other factors must be considered when siting a plant? Away from built up areas.within commuting distance of a town..good transport links to move the products Direct electric supply. 3.Why did the Anglesey Aluminum plant close? Energy costs too high (10-15% of all electricity used in Wales). Wylfa Powerstation got decommissioned so it was not sustainable to continue with the aluminum plant. Needed direct supply of electricity. 4. Although the raw materials for iron extraction can be found in Wales, why are they imported at Port Talbot? It is not sustainable on an economic or environmental basis to use those from Wales 5. Why is recycling metals more sustainable than extracting them? Conserves raw materials Uses less energy recycling aluminum requires 5%of the energy to extract it from bauxite Less electricity so smaller greenhouse emissions. Steel is an alloy harder and stronger than ion. Made by mixing molten metals. Changing the compositions changes properties eg % carbon in steel. Smart alloys return to their original shape when heated.

22 Energy 4 Energy Profiles An exothermic reaction is a reaction which gives out energy to its surroundings. Temperature goes up! Reactants Ea Ea activation energy minimum energy needed to start the reaction Energy given to surroundings H Products The energy change is negative as the arrow goes down. Combustion and neutralisation

23 Energy Energy Profiles An endothermic reaction is a reaction which takes in energy from its surroundings. Temperature goes down Ea Products Endothermic: In this reaction the energy of the products is higher than the energy of the reactants. Energy has been gained from the surroundings. Reactants H In this reaction the energy change is positive as the arrow goes up.

24 Energy of reaction = Breaking bonds Making bonds Hydrogen + Oxygen Water 2H 2 + O 2 2H 2 O H-H H-H Bond Energy (kj/mol) O=O 498 H-H 436 O-H 464 Energy = Breaking - Making Breaking = (2x 436) + (1 x 498) = 1370 KJ/mol Making = (4x464) = 1856 KJ/mol Energy = Breaking Making = = KJ/mol The energy put in to break the bonds is less than the energy given out in making bonds so the reaction would is exothermic and has a negative value.

25 More difficult? Hydrogen reacts with chlorine to form hydrogen chloride. Calculate the bond energy for Cl-Cl given that the energy for reaction is -185 KJ/mol and that the bond energy for H-H is 436KJ/mol and H-Cl is 432 KJ/mol. H 2 + Cl 2 2HCl H-H Cl-Cl H-Cl H-Cl Energy = Breaking - Making Breaking = (1x436) + (1 x Cl-Cl) = 436 +? KJ/mol Making = (2x432) = 864 KJ/mol Energy = Breaking Making -185 = Cl-Cl = Cl-Cl Cl-Cl = 243 KJ/mol

26 Decrease 5 The Fractional Distillation of Crude Oil 40 o C Gas Petrol Crude oil is a mixture of hydrocarbons containing carbon and hydrogen. Fractional distillation separates mixtures of liquids according to their boiling points. Naphtha (Chemicals) Paraffin Diesel Fuel oil Different fractions contain hydrocarbons of similar chain length. Crude oil is vapourised and cools as it goes up the column. As the fractions reach their boiling points, they condense. Heated Crude Oil 350 o C Lubricating oil Bitumen (roads) Fraction Boiling pt. and chain length The shorter the chain length the weaker the intermolecular forces between the chains and so the boiling points are lower they condense at the top of the column. The longer chains fractions are darker, harder to ignite (less volatile), burn less cleanly and are more viscous.

27 Global economic, political, social and environmental importance of the oil industry Global warming Climate change -crop yields etc Melting ice caps - Floods etc Acid rain ( from sulfur in fuel) Tree damage Affect on water systems kills fish etc. China s and India s economy growing greater energy supply! Increase in prices for oil Increase in living cost heating, transport, goods = inflation Non renewable source running out used to make plastics and medicines shall we burn it all?

28 Equations for combustion Combustion of any fuel requires oxygen and is an exothermic reaction giving out heat. CH 4 methane + 2 O 2 CO H 2 O oxygen carbon dioxide water C 2 H O 2 2 CO 2 + 2H 2 O Liquid would be seen = water Turns milky in presence of CO 2

29 Determining the amount of energy per gram released by burning fuel Key points: Same volume of water (100cm 3 ). Thermometer not to touch bottom of flask Record initial temp of water Record mass of fuel and burner Ignite Stop at set temp rise (40 0 c) Extinguish and reweigh burner and remaining fuel Caluculate: Temperature rise Mass of fuel used Energy from given equation. Mass of water = volume of water!

30 Hydrogen as an alternative energy source? Hydrogen is used as rocket fuel and in hydrogen fuel cells for cars. 1. What is the equation for the combustion of hydrogen? H 2 + O 2 H 2 O 2. Why is hydrogen better for the environment? -Made from water so renewable -Produces only water so no acid rain or global warming 3. It is produced by electrolysis, what is the main disadvantage of this process? -Large energy use/cost it is not carbon neutral! 4. What are the problems with storing it? - Bulky, pressurized containers - hazardous as forms explosive mixture with air.

31 Crude oil is a mixture of hydrocarbons called alkanes Alkanes Methane Ethane Propane CH 4 C 2 H 6 C 3 H 8 They have a general formula C n H 2n+2 Butane and pentane come next! These hydrocarbons are said to be saturated as they have single bonds between carbon atoms.

32 Cracking --Making more useful substances! Long chain alkanes cannot be used as fuels but using CRACKING the products are smaller alkanes and monomers called alkenes (Used for plastics!)

33 C n H 2n Alkenes Carbon can only form 4 bonds! Ethene C 2 H 4 Propene C 3 H 6 Alkenes are said to be unsaturated as they have a double carbon carbon bond. Number of carbons Alkane C n H 2n+2 Alkene C n H 2n 4 C 4 H 10 C 4 H 8 6 C 6 H 14 C 6 H 12

34 H Draw all the isomers of C 4 H 8 But-1-ene But-2-ene 2-methyl-prop-1-ene

35 H Draw all the isomers of C 5 H 12

36 Reactions of alkenes Making an alkene into an alkane using a nickel catalyst Bromine is toxic so bromine water is used as it is safer and easier to handle! Adding bromine to an alkene The test for alkenes. It starts orange/brown and goes colourless if an alkene is added. (Not if an alkane is used) A Bromoalkane

37 Polymerisation Vinyl chloride polyvinylchloride (PVC) -drain pipes Monomers are small reactive molecules that have a double bond. One of the bond breaks to allow molecules to join to form polymers. Plastics Ethene Polyethene bags, plastic bottles Flexible Strong Good insulators Resistant to corrosion Low density n Polypropene is used for ropes and crates Tetrafluoroethene Polytetrafluoroethene - Teflon non stick pans

38 Environmental concerns Burning Releases CO 2 Global Warming Releases toxic gases Landfill Filling up Some take hundreds of years to decompose Recycling Reduces burning and landfill Conserves crude oil supplies finite resource Uses less energy than production reducing fossil fuel use finite resource.