Chemistry 2.

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  • Chemistry 2.
    • Atomic structure and the periodic table.
      • Particles.
        • Protons are heavy and positively charged.
        • Neutrons are heavy and neutral (no charge).
        • Electrons are tiny and negatively charged.
      • Isotopes are; different atomic forms of the same element, which have the same number of protons but different numbers of neutrons.
      • Periodic table.
        • Elements in the same group have similar properties. This is because they have the same number of electrons in their outer shell.
          • The columns of the periodic table are called groups.
          • The  properties of elements (such as reactivity) often gradually change as you go down a group (as the atomic number increases).
        • The elements are arranged in order of increasing atomic number along each row.
          • The rows of the periodic table are called periods.
    • Ionic compounds and analysis.
      • In ionic bonding, atoms transfer (lose or gain) electrons to form positively or negatively charged atoms (or groups of atoms) called ions.
      • Insoluble salts.
        • To make pure, dry sample of an insoluble salt, you can use a precipitation reaction.
      • Flame tests.
        • sodium ions (Na+) give a yellow/orange flame.
        • Potassium ions (K+) gives a lilac flame.
        • Calcium ions (Ca2+) give a brick-red flame.
        • Copper ions (Cu2+) gives a blue/green flame
      • Testing for negative ions.
        • Testing for carbonates- check for co2 by bubbling the gas through limewater, if the water turns milky we know co2 is present.
        • Test for sulphates- for sulfate add dilute HCL  followed by barium chloride solution if a white precipitate is created then we know the original compound was a sulfate.
        • Test for chlorides- add dilute nitric acid followed by silver nitrate solution. A chloride gives a white precipitate of silver chloride,
    • Covalent compounds and separation techniques.
      • Atoms make covalent bonds by sharing a pair of electrons between two atoms.
        • 1) This way both atoms feel that they have a full outer shell, and that makes them happy.
        • 3) Each atom involved has to make enough covalent bonds to fill up its outer shell.
        • 4) When atoms make covalent bonds with one or more other atoms, they form a molecule.
        • 2) This way both atoms feel that they have a full outer shell, and that makes them happy.
      • Simple molecular covalent substances.
        • These make very strong covalent bonds to form small molecules of two or more atoms.
        • The forces of attraction between these molecules are very weak.
        • Melting and boiling points are very low because the molecules are easily parted from each other.
      • Giant molecular covalent substances.
        • All the atoms are bonded to each other by strong covalent bonds.
        • They have very high melting and boiling points.
        • They're usually insoluble in water.
        • Except for graphite, they don't conduct electricity.
      • Immiscible = liquids that won't mix.
        • Miscible = liquids will mix.
          • Mixtures  of miscible liquids can be separated by fractional distillation.
    • Groups in the periodic table.
      • Metals are on the left and middle of the periodic table.
        • Only elements on the far right of the table are non-metals.
        • Transition metals are found in the centre block.
          • These have high melting points.
          • Form very colourful compounds.
      • The elements in group 1 get more reactive as the atomic number increases.
        • Alkali metals are soft and have low melting points.
      • Group 7- very reactive.
        • Chlorine is a fairly reactive, poisonous, dense green gas.
        • Bromine is a dense, poisonous, orange liquid.
        • Iodine is a dark grey crystalline solid.
      • Group 0-  the noble gases, they're colourless don't react much, non -flammable, hard to observe.
    • Chemical reactions.
      • Exothermic.
        • An exothermic reaction is one which overall gives out energy to the surroundings in the form of heat, shown by a rise in temperature.
      • Rate of reaction.
        • Affected by: temperature, surface area, catalyst, concentration
      • A catalyst is a substance which changes the speed of a reaction, without being used up in the reaction.
      • Collision theory.
        • Particles have to collide in order to react, and they have to collide hard enough.
          • More collisions increases the rate of reaction.
          • Higher temperature increases collisions.
          • Higher concentration increases collisions.
          • Larger surface area increases collisions.
          • Catalysts increase the amount of successful collisions.
        • Faster collisions are only caused by increasing the temperature.
      • Endothermic.
        • An endothermic reaction is one which overall takes in energy from the surroundings int eh form of heat, show by a fall in temperature.

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