Chemistry Summary C2

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  • Created on: 04-04-16 14:04
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  • Chemistry Summary C2
    • Structure and bonding
      • Chemical bonding involves either transferring or sharing electrons in the outer shells of atoms
      • Atoms that lose electrons become positively charged ions. Atoms
      • When atoms share pairs of electrons they form covalent bonds
      • Ionic compounds are held together by strong electrostatic forces
    • Structure, properties and uses
      • When melted or dissolved in water, ionic compounds conduct electricity. Covalent compounds do not.
      • Diamond and graphite have different properties determined by their structures
      • Nanoscience refers to structures that are 1-100nm and of the order of a few hundred atoms
      • Metals consist of giant structures of atoms arranged in a regular pattern
      • Ionic compound have regular structures (lattices), high melting and boiling points
      • The properties of thermosoftening and thermosetting polymers depend on what they are made from and how they are made
    • Atomic structure, analysis and quantitative chemistry
      • Atoms of the same element can have different numbers of neutrons
      • The relative atomic mass (Ar) and relative formula (Mr) allow numbers of particles to be compared
      • The amount of product obtained is known as the yield
      • Elements and compounds can be identified using instrumental methods
      • The masses of reactants and products can be calculated from balanced symbol equations
      • A reversible reaction is one where the products of the reaction can react to produce the original reactants
    • Rates of reaction
      • Catalysts change the rate of chemical reaction but are not used up during the reaction
      • The minimum amount of energy that particles must have to react is called the activation energy
      • Chemical reactions can only occur when reacting particles collide. Collisions theory explains why changes to conditions affect rates
    • Exothermic and endothermic reactions
      • An exothermic reaction tranfers energy to the surroundings. An endothermic reaction takes in energy from its surroundings
      • If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction
    • Acids, bases and salts
      • Metal oxides and hydroxides are bases. Soluble hydroxides are called alkalis. Ammonia makes an alkaline solution to produce ammonium salts
        • Hydrogen ions make solutions acidic, and hydroxide ions make solutions alkaline
          • Soluble salts can be made from acids by reacting them with metals, insoluble bases or alkalis. Salt solutions can be crystallised to produce solid salt. Insoluble salts can be made by mixing solutions of ions so that a precipitate is formed
      • In neutralisation reactions, hydrogen ions react with hydroxide ions to produce water
    • Electrolysis
      • When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution
        • The electrode of sodium chloride solution produces hydrogen, sodium hydroxide and chrloine
      • Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite
        • During electrolysis, positively charged ions move to the negative electrode and are reduced, and negatively charged ions move to the positive electrode and become oxidised

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