Chemistry

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  • Chemistry
    • Combining Elements
      • Ionic Bonds
        • Between a Metal and a Non Metal
        • The Metal gives up electrons to gain a full outer shell whereas the non metal gains the electrons to get a full outer shell
        • The Metal becomes + and the non metal - (the charge number is the number of electrons gained or lost)
        • The opposite charges between the Metal and Non Metal hold the two atoms together and this is what holds the ionic bond
      • Atoms become stable (more happy) when they have a full outer shell, this also makes them unreactive
      • Covalent bonds
        • Between two Non Metals
        • The two elements share their electrons in the outer shells
        • the elements bond together in pairs of groups, these are called mollecules
    • Allotropes of Carbon
      • Diamond
        • Each carbon atom is covalently bonded to four other carbon atoms meaning each outer shell becomes full and stable
        • The covalent bonds are extremely strong and hard to break through making it a really solid material
        • Does not conduct electricity
        • It is good for cutting materials and drills as it is extremely resistant and has a high melting point
      • Graphite
        • only three electrons are covalently bonded therefore there's one electron is delocalised
        • The carbon atoms are arranged in layers but the delcoalised eletros flow between the layers therefore the intermollecularforces arent as strong as Diamonds
        • The layers of graphite slide over each other easily
        • Graphite can be used as a lubricant as it allows layers to slide, it can also be used to make electrodes for electrolysis as it is a good condutor
      • Fullerenes
        • groups of mollecules made from different amounts of atoms
        • cage like or tube structures
        • used as lubricants, methods of getting drugs into the body and to reinforce materials
    • Metals
      • mertallic bonding
        • loses the outer shell electrons but only to the space surrounding
        • a sea of metallic ions surrounded by delocalised electrons
        • the intermollecular forces between the ions and electrons hold the metal together
        • Most metals are relatively soft on their own as the layers an slide over eachother, therefore they must be turned into alloys to become harder
      • good conductors of electricity because delocalised electrons are free to move thus can carry the current through the structure
      • malleable because the ions although have an attraction and are held together, they arent in fixed positions therefore the layers can slide and move whilst the ions stilll hold their bonds
      • They also have high melting and boiling points because its hard to break their bonds
    • giant and simple covalent structures
      • giant
        • diamond, graphite and silicon dioxide
        • strong intermollecular forces
        • made from thousands of atoms
        • do not conduct electricity apart from graphite
        • Strong bonds which are hard to break threrfore have high melting and boiling points
      • Simple
        • Do not conduct electricity
        • weak intermollecular forces which are easy to break therefore have low milting and boiling pointe - most are gasses or liquids at room temperature
        • oxygen, water, sulphur
        • small numbers of atoms bonded to make mollecules
        • more soluble than giant covalent structures but not all are solluble
    • Nano particles
      • size ranges from 1-100 nanometers, they're made up of just a few hundred atoms
      • can be made naturally through burning fossil fuels, however they can also be manmade to suit specific purposes
      • have a large surface area in relation to the volume of partices
      • good for use as catalysts as they react quickly
      • silver nano particles used in sport gear and bandages to act as antibacterial with antimicrobial action
      • Also used to reinforce things such as tennis rackents, this means things can be mde lighter than then used to be
      • there have been questions as to the benefits and concerns wth using nano particles of health and the environment
      • Used as nano tubes for drug delivery where the drug isnt released until it reaches the necessary area, this means more strong and effective drugs can be used which would previoulsty have damaged other tissues
    • Chromatography
      • Paper chromatography
        • filter paper is the stationary phase, solvent is the mobile phase
        • food colouring is spotted next to the reference samples, when placed in the solvent the colours travels at different speeds thus are separated, the results in the sample are tested against the references to see what is present
        • Sometimes the colours that separate can leave invisibe spots, for these a locating agent is used, this is a substance which reacts with the chemicals to form a colour compound which can then be developed
        • The substance is constantly moving between the stationary and mobile phase so a dynamic equilibrium is created
        • if a substance is more attracted to the mobile phase it s position of equillibrium favours the moblie phase so the solvent moves further up the chromatogram
          • The substance is constantly moving between the stationary and mobile phase so a dynamic equilibrium is created
        • Thin Layer Chromatography (T.L.C)
          • uses the same procedure as paper chromotography but with silica plates
      • its a technique used to test whether a chemical substance is present within a mixtue,,,,,, it can also be used to purify substanes
      • Gas chromotography
        • Is a scientific process of chromotography
        • can be done on really small scales
        • sample is injected into the machine
          • the sample is heated to a gas in an overn
            • the carrier gas carries it along the column to teh detector and the detector logs the time each substance takes to pass
              • the longer it takes to pass the greater the retention time
        • gc-ms, gas chromotography, mass spectrometry
          • mass spectrometer weighs mollecules and gives the individual mollecular mass
            • Substances mus be ionised to be detected
          • this helps to identify substances
    • Isotopes and Relative atomic mass
      • Isotopes are elements with the same proton and electron number but different neutron numbers
      • elements are made up of isotopes
      • RELAVITE ATMIC MASS = (PERCENTAGE X ISOTOPE) +(PERCENTAAGE X ISOTOPE) ALL DIVIDED BY 100
      • an elements mass number is calculated by the agerage of both isotopes
    • equations
      • empirical formulae
        • given mass divided by R.a.m for all products in the compound
          • divide both numbers by the smallest outcome and put the result in a ratio
            • this is the answer
        • the smallest whole number ratio of the substancesin a compound
      • percentage yield
        • yield actually gained divided by the m,aximum possible yield x100
          • max possible yeild
            • product+ product

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