C2 Revision

C2 Revision

1. Isotopes

   • atoms of the same element with different masses

2. Relative Formula Mass

   • atomic mass of each element x number of atoms present in formula and add up e.g. (40x1) + (32x1) + (16x4) = 136

3. Ionic Bonding

   • Metal reacting with non-metal
     • metal atoms lose electrons and become positive ions
     • non-metal atoms gain electrons and become negative ions
     • Oppositely charged ions are electrostatically attracted

4. Ionic Lattices

   • oppositely charged ions attract each other in all directions
   • melting and boiling points are high because it is hard to separate the electrons from one another

5. Covalent Bonding

   • atoms of two non-metals combining
   • outer electron shells overlap, sharing
   • nuclei of both atoms in a cov. bond are positively charged
   • cannot conduct electricity because they have no charged particles to move around
     • cannot dissolve in water
       • weak intermolecular forces - easily broken, providing low bp and mp

6. Covalent Lattices

   • giant structures
   • diamond - each carbon atom joined to four other carbon atoms, hardest natural substance, cannot conduct electricity
     • tetrahedral structure
   • graphite - each carbon atom in layer is joined to three other carbon atoms, layers slide over one another because there are no covalent bonds, soft=lubricant and pencils, conducts electricity
   • silicon dioxide - similar to diamond structure

7. Thermosoftening

   • soften when heated and can be shaped when hot. shape will harden when it is cooled, but can be reshaped when heated up again. poly(ethene) is a thermosoftening polymer. tangled polymer chains can uncoil and slide past each other, making it a flexible material.
   • Thermosetting
     • Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily.

8. Alloys

   • in pure metal, all atoms are the same size and therefore are very soft because atoms can slide
     • alloys disrupt the regular lattice, preventing layers from sliding due to the myriad of different sized atoms

9. Gas Chromatography

   • separating technique
   • send gas solvent with analysed substances down a tube filled with solid material. components travel at dif speeds and are detected at the end.

10. OXIDATION IS LOSS, REDUCTION IS GAIN

11. Empirical Formula

    • 1. work out the relative formula mass
      • 2. find mass of element in compound
        • 3. divide by rel.form. mass x100 to get percentage

12. Percentage Yield

    • percentage obtained/maximum theoretical mass x100

13. Collision Theory

    • reactants must collide to form chemical reaction. increasing the temperature provides particles with more energy, so they vibrate more and heat up more, causing more collisions to happen.
      • to cause reaction, particles must collide with sufficient energy to break bonds - this minimum energy is called activation energy

14. Catalysts

    • chemicals that speed up relations but are not used up in the process
    • lowers the activation energy, so that more collisions happen at a faster rate, without having to build up to a higher minimum energy

15. Endothermic and Exothermic

    • Endothermic
      • heat enters the reaction - cools
        • electrolysis
        • thermal decomposition in a blast furnace
    • Exothermic
      • heat exits - warms surroundings through heat transfer
        • burning
        • neutralisation between acids and alkalis