GCSE AQA Chemistry New Spec Paper 1 Topic 1 TRIPLE SCIENCE

ONLY FOR NEW 2018 SPEC AQA CHEMISTRY TRIPLE SCIENCE

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  • Chemistry Paper 1 Section 1
    • Alpha Scattering Experiment
      • Ancient Greeks: everything is made of atoms.
        • Atoms are tiny spheres which cannot be divided.
      • 1897: Scientists discovered that atoms contain tiny negative particles. They called these electrons.
        • This showed that atoms are NOT spheres that cannot be divided. Atoms have an internal structure.
      • Plum Pudding Model
        • Suggested that an atom is a ball of positive charge with negative electrons embedded in it.
      • The Experiment
        • Scientists aimed a source of alpha particles through a gold foil.
          • Most of the alpha particles went straight through the gold atoms.
            • Therefore the centre of an atom must have a positive charge. Alpha particles that come close to this are repelled and change direction.
          • Sometimes an alpha particle bounced right back.
            • The centre of an atom must contain a great deal of mass. We now call the central part of an atom the nucleus.
    • The Nuclear Model
      • In the nuclear model, most of the atom is empty space. In the centre is a positive nucleus
        • In the centre is a positive nucleus which contains most of the mass of the atom.
          • The positive charge in the nucleus is due to tiny positive particles called protons.
        • Around the edge we fine negative electrons.
      • Niels Bohr
        • Proposed that electrons orbit the nucleus at specific distances.
        • Bohr's work agreed with the results of experiments by other scientists.
        • The orbits are now called energy levels or shells.
      • James Chadwick
        • Discovered that the nucleus also contains neutral particles called neutrons.
      • Atoms
        • Atoms have no overall charge because the number of electrons is the same as the number of protons.
    • Chromatography
      • Allows us to separate substances based on their different solubilities.
      • We call the paper the stationary phase because it does not move.
      • We call the solvent the mobile phase because it does move.
      • Paper Chromatography works because each chemical in the mixture will be attracted to the stationary phase to a different extent.
        • Chemicals that are strongly attracted to the stationary phase will not move very far.
        • Chemicals that are only weakly attracted will move further up the paper.
      • A pure chemical will only produce a single spot in all solvents.
        • The chemicals in a mixture may separate into different spots depending on the solvents.
      • If we use a pen instead of a pencil during the experiment, then the pen ink would move up the paper along with the solvent.
    • Fractional Distillation
      • In Fractional Distillation, we separate a mixture of different liquids.
        • These liquids MUST have different boiling points.
      • If the two liquids have got very similar boiling points, then it is much harder to separate them. We might need to carry out several rounds of fractional distillation..
      • Using fractional distillation to purify large volumes of liquid (crude oil) requires different equipment although the process remains the same.
    • Filtration and Crystallisation
      • Filtration
        • Separates an insoluble solid from a liquid
      • Crystallisation
        • Separates a soluble slid from a liquid
    • Simple Distillation
      • Used to separate a liquid from a solid if we want to keep the liquid.
      • How does it work?
        • Then the condense the vapour by cooling.
        • First we evaporate the liquid by heating.
      • Simple Distillation can be used to produce drinking water from sea water
        • However, a great deal of energy is needed fro simple distillation so generally it is not used to make drinking water.
    • Elements, Compounds and Mixtures
      • Elements
        • The periodic table shows us the elements.
        • There are around 100 elements.
        • In an element all the atoms are the same.
      • Compounds
        • Compounds contain two or more elements chemically combined in a fixed proportion.
        • compounds usually have totally different properties to the elements they are made of.
        • If we want to separate a compound back into its elements, then we need to use a chemical reaction to do so.
      • Mixture
        • In a mixture, we have different elements or compounds NOT chemically combined together
        • If we want to separate a mixture, then we use physical techniques rather than chemical reactions.
      • Molecules
        • Any elements chemically joined
    • Atomic Number and Mass Number
      • Atoms have no overall charge because the number of electrons is the same as the number of protons
      • Atomic Number = number of protons in the atoms of an element.
      • No. of protons = No. of electrons
      • Mass number = total no. of protons + total no. of neutrons.
        • Neutron no. = Mass number - atomic number
      • Isotopes
        • Isotopes are atoms of an element with different numbers of neutrons.
      • Ions
        • Atoms which have an overall charge. They have gained or lost electrons.
          • POSITIVE ions have LOST electrons.
          • NEGATIVE ions have GAINED electrons.
    • Electron Energy Levels
      • Electrons exist in energy levels (shells)
        • Each energy level can hold up to a maximum of 2(n2) electrons
      • Elements in group 0 (noble gases) have a full outer energy level.
    • Relative Atomic Mass
      • The average of the mass number of the different isotopes
      • It is weighted for the abundance of each isotope- how common each isotope is
    • Development of the Periodic Table
      • Columns = Groups
        • All the elements in a group have similar chemical properties.
          • This is because all the elements in a group have the same number of electrons in their outer energy levels.
      • 'Periodic': Elements with similar properties occur at regular intervals.
      • John Newlands
        • If we arrange the elements in order of atomic mass, every eight element reacts in a similar way.
      • Dmitri Mendeleev
        • Arranged elements in order of atomic mass.
          • Sometimes, he switched the order of elements so they fitted the patterns of other elements in the group.
        • Realised that some elements had not been discovered so he left gaps for them.
        • Mendeleev predicted the properties of the undiscovered elements based on other elements in the same group.
          • When the elements were discovered their properties were found to be almost exactly what Mendeleev predicted.
            • Other scientists now accepted that Mendeleev's table was correct.
      • Elements are arranged in order of atomic number (number of protons)
      • Group 0 was not fully discovered during Mendeleev's time.
    • Group 0 (Noble Gases)
      • The noble gases are very UNreactive elements.
        • This is because all noble gases have a full outer shell.
      • The boiling points increase as you go down the group (as the relative atomic mass increases)
    • Metals
      • When metals react they lose electrons to achieve a full outer energy level
        • This gives them the same electronic structure as a group 0 noble gas,
          • Metals always form positive ions.
    • Group 7 (Halogens)
      • Group 7 elements all have 7 electrons in their outer shells.
      • Group 7 elements form molecules with two atoms joined by a covalent bond.
        • Group 7 elements form covalent compounds when they react with other non-metal atoms.
      • Melting and Boiling points increase as we move down Group 7
      • Group 7 elements form ionic compounds when they react with metal atoms.
        • When any Group 7 element reacts with with a metal, the group 7 element gains one electron and forms a -1 ion.
      • When group 7 elements react with metals, the halogen gains an electron to achieve a full outer shell.
      • Sodium + Flourine bromide ----> sodium + bromine flouride
    • Group 1
      • All Group 1 metals have 1 electron in their outer shell.
      • Group 1 metals are soft.
      • All Group 1 metals react quickly with oxygen.
        • As you go down Group 1, the metals begin to react more quickly.
      • All Group 1  metals react very rapidly with chlorine.
      • Elements get more reactive moving down Group 1
        • Moving down the group, the outer electron is less attracted to the nucleus and easier to lose.
        • There is a greater distance between the positive nucleus and the negative outer electron.
          • The outer electron is shielded from the nucleus by the internal energy levels.
    • Transition Elements
      • All the transition elements are metals.
        • They are found in between group 2 and 3 in the periodic table.
      • Hard and Strong
        • Iron
      • High melting points
        • Apart from Mercury
      • High Density
      • Much less reactive than group 1 elements.
        • O2 CO2 H2O
      • Can form ions with different charges.
        • Fe2+ Fe3+ Ni2+ Ni4+

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