Chemistry 2

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  • Chemistry 2
    • Atoms, Molecules and Ions
      • Atom- smallest particle of an element
      • Molecule- A small group of atoms joined together
      • Ion- An atom/Group of atoms with an electrical charge (+/-)
      • Protons, Neutrons and Electrions
        • Protons have a mass of 1 and charge of +1
        • Neutrons have a mass of 1 and charge of 0
        • Electrons have 0 mass and -1 charge
      • Atom number= number of protons.
        • Number of protons= Number of electrons
          • Mass of an atom= protons +neutrons
    • Electronic structure
      • 2882
      • Ionic Bonding
        • Takes place between a metal and a non metal
        • The metal atoms lose their outer shell electrons to form positive ions
        • The non metal atoms gain these electrons to fill their outer shells and form negative ions
        • The positive and negative ions attract each other in a lattice
      • Covalent Bonding
        • Covalent bonds are formed between 2 non metals
        • The atoms share electrons in order to complete their outer shells
        • The new particles formed are neutral molecules
      • Structures of substances
        • Simple molecular
          • Low melting and boiling points
          • Soft/weak
          • Not conductors of electricity
        • Giant covalent
          • High melting p[oint
          • Hard/Sturdy
          • Not conductors of electricity
          • Insoluble
        • Giant metallic
          • Strong/Sturdy
          • High melting point
          • Malleable (can be bent)
          • Good conductors of electricity and heat
          • Shiny
        • Giant ionic
          • High melting and boiling points
          • Hard but shatter easily
          • Conduct electric once molten or dissolved
          • Soluble in water
    • Rates of reaction
      • Catalysts
        • Substances which increase rate of reactions without being chemically changed- lower activation energy (e.g enzymes are biological catalysts)
      • Temperature
        • Rise of temp. will increase the rate of reaction- makes particles move faster and increases collisions. Cooling will make reactions slower because particles move slower.
      • Concentration
        • Reactions happen more quickly when concentrated solutions are used because the particles are closer and so are more likely to collide
      • Pressure
        • When gases are at high pressure the particles are closer and so more likely to react
      • Surface area
        • Solids in powder form will react quicker than solids in lump form- powder particles have more surface area exposed to the reactant. If a lump is used only the outer area can react
      • Measuring rate of reaction
        • Rate= Amount of product formed divided by the time
      • Energy changes in reactions
        • Give out energy- Exothermic- cause temp. to rise.
        • Take inenergy- Endothermic- cause temp to fall
        • Reversible reactions
          • If a reaction is exothermic in one direction, it will be endothermic in the other direction and the amount of heat given out by the exothermic reaction will be equal to the amount of heat taken in by the endothermic reaction
    • Electrochemistry
      • Conductors
        • Metals and graphite are the only solids which conduct electricity. Molten metals also conduct.
      • Electrolytes
        • Liquids which conduct electricity. They are ionic substances that are dissolved or melted
      • Electrolysis
        • This is when an electric current passes through an electrolyte.
        • Electrons enter the solution through the negative electrode (cathode), cause a chemical change and leave by the positive electrode (anode)
    • Acids, Bases and Alkalis
      • Acids
        • Corrosive/pH less than 7, react with and neutralise bases and produce hydrogen (H+) ions in water
      • Bases
        • React with an neutralises acids, generally solids, metal oxides and metal hydroxides are bases, alkalis are soluble bases, alkalis produce OH ions in water
      • Salts
        • Generally compounds of metals, formed when an acid neutralises a base. Salt is formed when hydrogen in an acid is replaced by metal atoms
      • Reactions of acids
        • Sulphuric acid gives sulphates
          • Nitric acid gives nitrates
            • Hydrochloric acid gives chlorides
        • ACID + BASES = SALT + WATER

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