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  • Created by: Brooke
  • Created on: 15-07-13 10:51
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  • Atoms
    • Dilution of coloured solutions
      • When potassium manganate(VII) crystals are disolved in water, a purple solution is formed. A very few tiny crystals can produce a highly intense colour
        • When this solution is diluted several times, the colour fades, but does not disappear until a lot of dilutions are made
          • this indicates that there are a large number of particles of potassium manganate(VII) in a very small amount of solid
            • if this is true, then the particles of potassium manganate(VII) must be very tiny
    • Diffusion
      • Particles will move to fill the space available to them. They can do this in both liquids and gases.
      • An example is the diffusion of bromine from one flask to another.
        • After 5 minutes the bromine gas has diffused into the left-hand flask
          • This happens because both air and bromine particles are moving randomly and there are large gaps between the particles
            • the particles can therefore easily mix together
      • Diffusion also takes place in liquids, only more slowly since the particles in a liquid are closely packed together and they move more slowly than in a gas
    • Atoms and molecules
      • ATOMS are made up of smaller, sub-atomic particles called protons, neutrons and electrons
      • Most molecules are made up of two or more atoms covalently bonded together
        • However, the noble gases (helium, neon, argon, krypton, xenon and radon) exist at room temperature and pressure, so for them the atom and the molecule are the same
      • Molecules that contain only one atom are called MONATOMIC MOLECULES
    • Elements, Compouds and Mixtures
      • Compounds are chemicals made from atoms of different elements joined by chemical bonds. They can only be separated by a chemical reaction.
        • Elements, and compounds have their own chemical proprties. The properties of a compound are likely to be different from the elements that have been used to make it
        • Since the elements in a compound are chemically joined together, they can only be sparated from one another by carrying out a chemical reaction
          • Sometimes heating the compound will be sufficient to make the reaction happen. For example, mercury oxide decomposes into mercury and oxygen on heating
            • This is known as THERMAL DECOMPOSITION
          • On another occasion, electricity will decompose the compound the compound. For example, if an electric current is passed through molten lead(II) bromide, it breaks down into lead and bromine
            • This is known as ELECTROLYSIS
      • A mixture is made from different substances that are not chemically joined.
        • a mixture will have the properties of each substance that has been used to make it
        • Separation of mixtures
          • Filtration
            • To separate an undisolved solid from a mixture of the solid and a liquid/solution (e.g sand from a mixture of sand and water
          • Evaporation
            • To separate a dissolved solid from a solution, when the solid has similar solubility in both cold and hot solvent (e.g sodium chloride from a solution of sodium chloride in water)
          • Crystalisation
            • To separate a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold (e.g copper(II) sulfate from a solution of copper(II) in water)
          • Simple Distillation
            • To separate a liquid from a solution (e.g water from a solution of sodium chloride in water)
          • Fractional Distillation
            • To separate two or more liquids that are miscible with one another (e.g ethanol and water from a mixture of the two)
          • Paper Chromatography
            • To separate substances that have different solubilities in a given solvent (e.g different coloured inks that have been mixed to make black ink)


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