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Periodic Table Development Dalton’s Periodic Table Arranged in order of atomic mass; Symbols are shown for every element Different names were given(old fashioned) Newlands Octaves 8 octaves-similar property Arranged in order of atomic mass; Periodic pattern of properties but this pattern eventually broke down Mendeleev’s Table Combined both of atomic number and octaves Similar to what we use today Arranged them so that groups with similar properties fell into vertical columms in the table Properties of group 0 Helium:protons:2 neutrons:2 electrons:2 Noble gas are stable with a general equivalence of numbers of protons and electrons. They have a full outer shell which makes them stable and generally unreactive They were the last elements to be discovered because they are generally unreactive and they are gases. Colourless and monatomic. Their boiling point and density increases from top to down. Helium is used to fill airships Element Number of Density Boiling point Uses electrons He 2 4 Intermolecular Party balloons Ne 10 20 Forces Car light Ar 18 40 Increases Double-blazing Kr 36 84 When Anesthetic Xe 54 131 Going Car light Rn 86 222 Downwards Radiotherapy Group 1 Alkali metals Coated in oil to stop them from reacting 1 electron in the outer shell Lithium 3 protons 4 neutrons and 3 electrons Sodium 11 protons 12 neutrons and 11 electrons Potassium 19 protons 20 neutrons and 19 electrons More reactive as you go down the group as the nucleus is positive, electron is further away This is the same for all elements in groups. Hydrogen: lit splint and squeaky pop Less attraction between outer shell and electron The melting and boiling points decrease as there is less energy needed to boil the electron Group 7-halogens Sodium+chloride-sodium chloride Fluorine Chlorine Proton 9 17 Neutron 10 18.5 Electron 9 17 Electronic confirmation 2,7 2,8,7 Elements Electrons Density Reactivity Melting point, boiling point Fluorine(gas) 9 Increases Decreases Increases Iodine(gas) 53 As As As Chlorine(g) 17 You You You Bromine(aqueous) 35 Go Go Go Astatine(solid) 85 Down Down Down Reactivity down the group decreases; harder to gain electrons as the atom gets bigger. More outer shells Fluorine isn’t used a lot; too reactive Chlorine-used in swimming pools kill bacteria When group 1 reacts with group 7, a metal halide is formed Transition metals Name of compound Formula Description Nickel sulphate NiSO4 Green, toxic, aqueous Copper chloride CuCl2 Blue Cobalt chloride CoCl2 Pink/red toxic Chromium chloride CrCl Black/dark Iron chloride FeCl2 Yellow Fe3+ Cl- Name of metal Can it be bent? Can it float on Description water? Copper Yes No Zinc Yes No Iron Yes No Conclusion: most of the transition metal compounds have colour. Dense metals,strong,good conductor, high boiling points Structure of metals: metallic bonding +-+-+-+-+-+-+-+-+-+ Strong electrostatic forces of attraction More neutrons, more protons between oppositely charged ions Dull grey The electrons on the outer shell all go through the same energy level, for example:3D HARD water Hard water contains ions that exchange ions that can damage the pipes and applicances Rainwater is naturally weak acidic Therefore it can dissolve minerals from rocks. Carbonic acid+ calcium carbonate=calcium hydrogen carbonate H2CO3(aq)+CaCO3(s)=Ca(HCO3)2 (aq) The presence of calcium ion and magnesium ions in the water makes it hard. The type of rock will determine whether it is hard or soft water Soft water readily forms lather with soap, but it is more difficult to form lather with hard water. Soft water exists in Cornwall, Wales and Lake District, it has low levels of dissolved calcium and magnesium compounds, while the water in other parts of the country have hard water because it has higher levels of dissolved calcium and magnesium compounds. Soft water will make appliances last longer Hard water: water that contains magnesium and calcium ions and does not readily form lather with soap. Soft water: water that readily forms lather with soap Scum;insoluble precipitate that forms with soap and hard water Removing hard water Temporary and permanent hard water Formation of limescale on the inside of the kettle softens the water( removes Mg, Ca ions) Permanent hard water softens from sulphate cannot be removed by heating. But we can soften it by adding sodium Temporary:Ca2+ + 2HCO3=CaCO3+ H2O+CO2 1. Boiling the hard water containing hydrogencarbonate ions 2. Carbonate io0ns react with Ca/Mg Therefore removing using washing soda adding sodium carbonate This is the same reaction as formation of limescale but this time it happens where and when we want it to. Hard water ions are swapping places with soft water such as Sodium and potassium Most hard water makes it difficult to wash ourselves. As well as this, it also makes it difficult to clear the bath/sink when we have finished. This is because hard water contains dissolved compounds that react with the soap to form scum. The scum floats on the water and sticks to the bath. Calcium carbonate reacts with the weakly acidic solution. The calcium hydrogencarbonate formed is soluble in water, therefore calcium ions, Ca2+(aq) get into the water, making it hard. This equation describes what happens: CaCO3(S)+H2O(AQ)+CO2(AQ)=Ca2+(aq)+2HCO3(AQ) Calcium ions in drinking water helps in the development in strong bones and teeth. There is also evidence that hard water helps to reduce heart disease Sodium stearate(soap)+Ca2+ ions (calcium)= calcium stearate precipitate (scum)+Na+ions soluble in water Hard water contains calcium and for magnesium ions. These react with soap to form scum. Hard water can also produce scale when it is heated. This is a poor conductor of energy and makes kettle and water heaters less efficient. Hard water is better for teeth and bones than soft water. This helps reduce heart disease. Calcium is dissolved from rocks which are washed into the river, into the sea and evaporated into the clouds which will rain, this could contain hard water. 2HCO3(AQ)+CO3-(AQ)=H2O(L)+CO2(G) Purification of water Clean water is water without harmful bacteria debris or sediment in it. 1. The screen take out the large debris to make the water clean of big rocks. 2. The settlement tank produces sedimentation and the water gets to take out from the top to get away. 3. Al2(SO4)2+ lime will coagulate small particles in order for them to be filtered through the fine filter 4. Chlorine is added and Ph is then checked for the safety of home water Calorimetry Q=m*Ct Energy change=mass*specific heat capacity*temperature change Exothermic VS Endothermic Breaking a bond requires energy. Making a bond releases energy. To measure the amount of energy released when a fuel is burnt, you can simply burn the fuel and use the flame to heat up some water, this is called calorimetry 1. Put 50g of water in a copper can and record its temperature(copper is used because it conducts heat so well) 2. Weigh a spirit burner containing methylated spirits, along with its lid. 3. Put the spirit burner underneath the can, and light the wick. Heat the water, stirring constantly, until the temperature reaches about 50oc 4. Use the lid of the spirit burner to put out the flame and measure the final temperature of the water 5. Weigh the spirit burner and lid again Calorimetry of solutions Minimise flame disturbance Ensure complete combustion Calorimeter- put a lid on it Polystyrene cup lets no energy out Have the same specific heat capacity as water Stir to make sure chemicals are mixed properly (assuming polystyrene cup does not leak out heat) Effect of catalysts Bond breaking=energy in endothermic Bond making=energy out, exothermic For a reaction to happen particles need to collide with each other with enough energy to break bonds Catalysts are specific for each reaction-provide a lower activation energy-lower energy requirements Catalysts help to control reactions, they are very expensive, often precious metals. During the reaction catalysts aren’t used up Hydrogen as a fuel Burning fossil fuels release carbon dioxide which cause global warming, increasing the temperatures causing destruction of habitats and causing early migration. Burning fossil fuel releases sulfur dioxide which cause acid rain. This also makes nitrogen dioxide which cause smog, blocks out sunlight and damage lungs. 2H2+O2=2H2O Advantages: Environmentally friendly More efficient than petrol and diesel Only exhumes water Disadvantages: Very flammable; may explode Expensive fuel of hydrogen Can’t drive it for long distances Can’t find hydrogen taps in petrol stations; The car is quite expensive The advantages of using hydrogen are that it is environmentally friendly, a renewable energy source and has many ways to extract it, no global warming because there is no carbon dioxide released. Less energy is produced, the gas is explosive; the volume of storage is big, uses electrolysis to produce hydrogen All metal ions are positive Metal ions Colour of flame Li+ Crimson K+ Lilac Na+ Yellow Ca2+ Red Ba2+ Green Method for flame tests 1. Dip the nichrome wire into the concentrated HCl, then dip it into the metal you want to test 2. Burn the nichrome wire on a Bunsen burner, then identify the colour Get equipment 1. Dip in HCl to clean nichrome wire 2. Place in flame to dry HCl 3. Place in HCl/ water to ensure powder sticks 4. Place in flame, observe colour 5. Use colour to identify + ions Test for negative ions Test for halides Dilute nitric acid(HNO3) followed by silver nitrate(AgNO3) Name of compound Effect of adding HNO3+AgNO3 KI Yellow silver iodide KB Cream silver bromide KCl White silver chloride Titrations Burette Rinse through acid first Fill at a safe height Shut tap when filling Make sure tap is full Watch for air bubbles Precision: read to 2 decimal places, for example 10.05 can be 0/5 Pipette Rinse with alkali first Fill to line meniscus Do not hold the bulb Watch for air bubbles A titration is used to measure accurately how much acid is needed to react completely with a known amount of alkali-this is used to work out the concentration HCl+NaOH=H2O+NaCl Hydrochloric acid+ sodium hydroxide=water+ sodium chloride Method: Rinse burette with water and then rinse with acid/alkali Fill the burette with the acid until it reaches 0. Use pipette to measure out 25ml of the unknown alkaline and put it into a conical flask Add indicators to the flask Use burette to fill flask with acid until indicator becomes neutral Equilibrium and reversible reactions a reversible reaction is a reaction that goes in both directions dynamic equilibrium is a balance between continuous chemical processes Closed systems: reactant and products remain in one reaction We can change equilibrium by changing temperature and pressures Changing temperatures A+B=C+D Reversible reactions are always exothermic in one direction and endothermic in the other direction If you raise the temperature favours the endothermic direction So that it uses up extra heat and keep equilibrium in the same direction Decrease temperature favours exothermic We can alter the position of the equilibrium if we continue to decrease or increase the temperature or pressure The Haber Process Ammonia is an important compound in the manufacturing of fertilizer and other chemicals such as cleaning fluids and floor waxes It is made industrially by reacting nitrogen in the Haber process. It is a reversible reaction as it never goes into completion Nitrogen+Hydrogen=Ammonia N2+ 3H2 =2NH3 Steam is reacted with methane to make hydrogen Hydrogen is mixed with nitrogen, obtained from air. The gases are compressed to 200 atmospheres, heated to 450oc The gases are passed over an iron catalyst Ammonia gas is produced, then cooled into a liquid Liquid ammonia is pumped off to be sold Unreacted nitrogen and hydrogen are recycled. Compromise due to the cost of machinery Includes pressure favour forward reaction due to fewer molecules Adding heat favours the endothermic reaction(backwards) But if we cooled the reaction down, the rate of reaction would be too slow so we increase temperature to increase rate of reaction Compromise between maximum yield and rate of reaction Iron catalyst: speeds up rate of reaction by creating an alternative pathway with lower activation energy, makes it cheaper We do not lower the temperature because we do not lower the rate of reaction. We do not increase the pressure because it is too expensive Alcohols CH4 Methane C2H6 Ethane C3H8 Propane More carbons, the longer chain length, longer intermolecular force. Length of carbon chain and boiling points. As we increase chain length, the stronger intermolecular force. Length of carbon chain and boiling point Alkanes and alkenes C2H5OH Ethanol -OH: functional group for alcohols Alcohol could heighten aggression Lack of coordination causes dehydration, irreversibly kills liver Homologus series: group of compounds which contain same things For example: propanol, ethanol and methanol Homologous: general formula of alcohol Alkane CnH2n+2 Alkene CnH2n Alcohol CnH2n+1OH Alcohols -take 2 Alcohols are fuels Methanol+ oxygen=carbon dioxide+ water 2CH3OH+3O2=2CO2+4H2O Ethanol+ oxygen= carbon dioxide+ water 2CH3OH+ 3O2= 2CO2+ 4H2O Ethene+ Steam= ethanol C2H4+H2O=C2H5OH Methanol and ethanol can dissolve everything water can and more! They can dissolve fats which water can’t therefore are very useful in industry Ethanol is used in perfumes(mixes oils smell and water) Meths-used for cleaning paint, very poisonous to drink so a purply dye is added The first four alcohols are soluble in water and form neutral solutions At the hydrocarbon chains get longer the alcohols become less soluble and very long hydrocarbon chains tend to be insoluble as they are hydrophobic 2Na+ 2C2H5OH= 2C2H5Ona+ H2 Sodium+ ethanol= sodium ethoxies+ hydrogen Metal+ alcohol= metal ehoxide+ hydrogen Carboxylic acid Ethanoic acid CH3COOH Homologus series All acids ionize to give H+ Dissociate less- weaker acids Carboxylic acid do not fully dissociate Ionization Strong red (HCl) Reactions with carbonates Acid+ carbonates=salt+ water+ carbon dioxide Ethanoic acid+ sodium carbonate=sodium ethanoate+ water+ CO2 CH3COOH(aq)+Na2CO3=2CH3COONa+ H2O+ CO2 Ethanoic acid has less hydrogen in the reaction so hydrogen doesn’t fully ionize Acid+ base=salt+ water Ethanoic acid is used for flavouring and preservative Ethanol+ oxygen=ethanoic acid+water C2H5OH+O2=CH3COOH+H2O Esters are homologus series of carbon compounds made from carboxylic acids and alcohols Alcohol+”-oc-“ acid= ester+ water Ethanol+ ethanoic acid= ethyl ethanoate and water Extremely volatile and flammable, so esters are dangerous Non-toxic=don’t react or dissolve in water They do dissolve into alcohols and other soluble solvents A solvent is a liquid that dissolves substances Some are toxic in large quantities Flammable and heavier than air Make long chain esters being polymers.