C3

atoms, has orbiting electrons- have positively charged nucleus and negitively charged electrons. electrons move around nucleus in layers (shells). atoms form bonds to make molecules/compounds. electrons involved in making bonds. sometimes as atom loses or gains 1 or more electrons (becomes positive if loses atom, negative if gain).

displayed and molecular formulas- CH4 is a molecula formula. shows the number and type of atoms in a molecule. this is the displayed formula. it shows the atoms and covalent bonds in a molecule:  

CH3(CH2)2CH3, the 2 after the bracket means that there are 2 lots of CH2. so altogether there are 4 carbon atoms and 10 hydrogen atoms.

formulas to remember- carbon dioxide= CO2. hydrogen= H2. water= H2O. hydrochloric acid= HCl. calcium chloride= CaCl2. carbon monoxide= CO. magnesium chloride= MgCl2. calcium crbonate= CaCO3. sulfuric acid= H2SO4. magnesium sulfate= MgSO4.

chemical changes shown using equations- example: methane burns in oxygen giving carbon dioxide and water. word eq= methane + oxygen -- carbon dioxide + water. molecules on left are reactants. molecules on right called products.

symbol equations- show formulas of reactants and products. example: 2Mg (magnesium) + O2 (oxygen) -- 2MgO (magnesium oxide).

symbol equations balanced- have the same number of atoms both sides.

example: H2SO4 + NaOH -- Na2SO4 + H2O

method- 1) find element that doesn't balance and pencil in number. 2) may create imbalance if so, pencil in another number. 3) carry on until it's baalnced.

answer: H2SO4 + 2NaOH -- Na2SO4 + 2H2O

combustion is an exothermic reaction- best example is burning fuels. endothermic reactions are less common. one example is thermal decomposition, heat supplied to cause compound to decompose.

temperature change help decide if reaction's exo or endo- measure amount of energy released by  chemical reaction by taking temp of reactants, mixing them in a polystryrene cup and measuring temp of solution. adding acid to alkali is exo. meausure temp of alkali before you add acid and mixing- see increase in temp. dissolving ammonium nitrate in water is endo. adding couple of spatulas of ammonium nitrate to a polystyrene cup of water- drop of temp.

energy supplied to break bonds, energy released when bonds form- during chemical reaction, old bonds broken, new formed. energy supplied brek bonds is endo. energy released when new bonds form is exo. in exo, energy released in bond formation is greater than energy breaking old bonds. endo, energy required to break old bonds is greater than energy released when new bonds form.

"calorimetric" experiment- heating water by burning liquid fuel. measure how much fuel you've burnt, and temperature change of water, can work out how much energy supplied by each gram of fuel. water's specific heat capacity is 4.2 J/g/oC- 4.2J to riase temperature of 1g of water by 1oC. same experiment for different fuels, can compare energy transferred per gram. if fuel has higher energy content per gram, need less fuel to cause same temp rise.

calorimetric method- as much heat as possible go into heating up water. reducing draughts- use screen to act as draught excluder. put fuel into spirit burner and weigh burner full of fuel. measure out water into copper calorimeter, take temp of water- put under calorimeter and light wick. when heat from burner made water temp rise by 20-30oC, blow out spirit burner, make note of highest temp water reaches.

calculations- find mass of fuel by subtracting final mass of fuel/burner from initial mass. energy transferred (J) = mass of water (g) x specific heat capacity of water (J/g) x temp change (oC).  Energy given out per gram (J/g) = energy released (J) / mass of fuel burned (g).

fair test- same experiment several times, using different fuel. everything except fuel keep same. same amount of water, apparatus and water start/finish same temp.

different rates- 1 of slowest is rusting of iron. other slow reactions include chemical weathering (acid rain), moderate speed is metal reacting with dilute acid, produces stream on bubbles. burning is fast reaction, explosion is faster.

experiment to follow reaction- rate of reaction produces a gas can observed measuring how quickly gas is produced: measure change in mass- reaction on balance mass falls as gas released. measure volume of gas given off- gas syringe to measure volume of gas given off.

particles must collide with energy to react- rate of reaction depends on: collision frequency of reacting particles, more collisions= faster reaction. energy transferred during collision. particles have to collide with enough energy to be successful.

more reactant used, more product formed- amount of productr get from reaction depends on amount of reactant start with. more reactant means more particles. have more reactions, create more product. amount of product get id directly proportional to limiting reactant. limiting reactant used up, reaction can't continue, can't get more product. might be some of other reactant left (excess)

more collisions- reactions happen if particles collide. increase number of collisions, reaction happens quickly. factors lead to more collisions:

increasing temp- when temp increased particles move faster, have more collisions. also increases energy of collisions. higher temp more particles colliding with enough energy make reaction happen.

increasing concentration- more particles of reactant in same volume, makes collisions more likely. in gas increasing pressure, molecules more crowded, collisions increase.

smaller solid particles- if solid breaking it in pieces will increae surface area. particles around it will have more area to work on, frequency of collisions increase. fine powders of combustible materials disperse in air, burn fast, as have big surface area. if spark will explode.

catalyst- tend to be fussy about what reactions they catalyse. works by giving reacting particles a surface to stick to where can bump into each other- reduces energy needed by particles before react. overall number of collisons not increased, number of successful collisions are.

relative atomic mass, Ar- elements have 2 numbers bigger one is atomic mass.

relative formula mass, Mr- compound like MgCl2 then it is just all relative atomic masses added together. Mg + (2 x Cl) = 24 + (2 x 35.5) = 95

compound with brackets- like Ca(OH)2. small number 2 after bracket means there is 2 of everything in the brackets. Ca + (O + H) x 2 = 40 + (16 + 1) x 2 = 40 + 34 = 74.

chemical reaction, mass is conserved- during chemical reaction, no atoms are destroyed or created. same number and types of atoms on each side of reaction equation. no mass is lost or gained- mass is conserved. example: 2Li + F2 -- 2LiF. adding up relative formula masses on each side of equation, see that mass is conserved. method: (2 x 7) + (2 x 19) -- 2 x 26. 14 + 38 = 52. 52 -- 52 mass is conserved. only product formed is lithium fluoride, 14 + 38 = 52g produced. masses for this reaction will be in same proportion as this. multiplying or dividing masses by same number gives you other sets of reacting masses.

steps:

1) write out balanced equation

2) work out Mr- for two bits you want

3) apply the rule: divide one, then multiply to get all (apply to substance they give information about then the other one)

atom economy- lot of reactions make more than one product. some are useful, otrhers waste. atom economy of reaction tells you how much of the mass of reactants is wasted when manufacturing a chemical. atom economy = total Mr of desired products / total Mr of all products x 100. 100% atom economy means all atoms in reactants have been turned into useful products. the higher the atom econmy, greener the process.

high atom econmy better for profits and enviroment- reactants with low atom economy use up resources quickly, and make waste to be disposed of. makes reactions unsustainable- raw materials will run out and waste go somewhere. low atom economy reactions aren't profitable. raw materials expensive to buy, waste products expensive to remove/dispose of responsibly. find use for waste products, come up with reaction that gives useful "by-products". reactions with highest atom economy are ones that have one product. have atom economy of 100%. 

percentage yeild- more reactants strat with, higher actual yield. percentage yield doesn't depend on amount of reactants, but percenatge. percentage yeild = actual yeild (g) / predicted yield (g) x 100. is always between 0 and 100%. 100% yied, got all products expected to get. 0% yield, no recatants converted into product. industrial process want high percentage yield to reduce waste ad costs.

yileds less than 100%, reasons- evaporation: liquids evaporate- even more when heated. not all reactants react to make product: reversible reactions, products turn back into reactants. filtration: when filter liquid to remove solid particles, always lose a bit of liquid. if want to keep liquid, lose the bit that remains with the solid and filter paper. if want to keep solid, some gets left behind when scraped off filter paper. transferring liquids: lose liquid when transferred from one container to the other. some left behind on inside surface of old container.

manufacturing process depends on product- batch production: pharmaceutical drugs are complicated to make, low demand. batch production most cost-effective way to produce small quantities because: flexable- different products amde using same equipment. start-up costs are low- small-scale, multi-purpose equipment bought off shelf. disadvantges: labour-intensive- equipment set up manually controlled and cleaned. hard to keep same quality from batches. continuous production- large-scale industrial manufacture of popular chemicals. production never stops, dont waste time emptying reactor/setting up. runs automatically. quality consistant. but start-up costs to build plant is huge, isn't cost effective to run at less than full capacity.

pharmaceutical drugs cost alot for- research and development- finding suitable compound, testing, modifying until ready. trailing- no drug can be sold until gone through tests. manufacturer has to prove drug meets legal requirments. manufacture- multi-step batch production is labour-intensive, can't be automated. other costs include energy and raw materials. raw materials often rare, sometimes extracted from plants. to extract from plant: crushed, boiled  and disolved in a suitable solvent, then extract substance by chromatography- spots of different chemicals move up paper at different speeds, cut out right blob and dissolve it off paper, discard impurities.

diamond- lustrous and colourless. ideal for jewellery. each carbon atom forms 4 covalent bonds in rigid giant structure, makes diamond hard. ideal for cutting tools. strong cobalent bonds take a lot of energy to break and give diamond high melting point. doesn't conduct electricity; has no free electrons or ions.

graphite- black, opaque and shiny. each carbon atom only forms 3 covalent bonds, creating sheets of carbon atoms, free to slide over to each other. layers lead together weakly, slipery and can be rubbed off- good for lubricating material. high melting point- covalent bonds need energy to break.only 3/4 of carbons out electrons are used in bonds, lots of delocalised electrons that can move. conducts electricity.

diamond and graphite- carbon can form lots of covalent bonds with itself, can form giant molecular structures, because of this they are strong, have high melting points, don't dissolve in water. don't conduct electricity; no free electrons.

fullerenes- used to cage otther molecules. structure forms around another atom or molecule, which trapped inside, could be new way of delivering drug. joined together to form nanotubes- huge surface area, so help make industrial catalysts- individual catalyst molecules could be attached.