Chemistry

1. Between + &- ions
2. Atoms turn into Ions by gaining or losing an electron
3. E.g Mg^2+ 0^2-
4. High melting points
5. Don't conduct electricity when solid
   1. Only conduct when molten or in soluion

1. Between two non-metals
2. Shared pair of electrons
3. Dot cross diagrams
4. Strong Intermolecular forces
   1. Low Boiling point
   2. High Melting point
5. The number of covalent binds = 8 - group number
6. Double and triple bonds
   1. Double is 2 pairs of shared electrons
   2. Triple is 3 pairs of shared electrons

1. Simple Molecules
   1. Properties
      1. Low melting and boiling points
         1. Weak intermolecular fores
   2. Non-conductive
   3. Few atoms joined together
2. Giant Covalent structures
   1. Macromolecules E.g
      1. Diamond

         Nota:

         • Very hard high melting point each carbon atom is joined to four others.
      2. Graphite

         Nota:

         • Is a form of carbon. It forms layers. Each layer is joined by only three other carbon atoms. Graphite is soft used as a lubricant conducts electricity
      3. Silica

         Nota:

         • Similar to diamond but silicon and oxygen atoms instead of carbon
3. Polymers
   1. LDPE
      1. Many branches
      2. Weak
      3. 85C maximum useable temperature
   2. HDPE
      1. Few branches
      2. Strong
      3. 120C maximum useable temp.
   3. Thermosoftening polymers
      1. No cross links
      2. can be reshaped when heated
   4. Thermosetting polymers
      1. Once heated cannot be reshaped
      2. Polymer chains joined with cross links

1. Uses
   1. To remove rust from acids
   2. As an electrolyte
2. Found in:
   1. Stomach (hydrochloric acid)
   2. Lemons (citric acid)
   3. Vinegar (acetic acid)
3. All contain hydrogen ions (H+)

1. All alkalis are bases but bases aren't always alkali

   Nota:

   • Fried egg diagram
2. All metal oxides and hydroxides are bases
   1. Hydroxides are often alkalis
      1. NaOH & KOH

1. Acid Neutral Alkali Red Green Blue
2. Universal Indicator

Nota:

• HCl + NaOH -> H2O +NaCLHCl(aq) +NaOH(nq) -> H2O(l) + NaCl (aq) H+(aq) + Cl-(aq) +Na+(aq) + OH-(aq) -> H20(l) +Na(aq) + Cl (aq)

1. Soluble
   1. Most carbonates and hydroxides
   2. lead sulphate & barium sulphate
   3. lead & silver chlorides bromides & iodides
2. Insoluble
   1. sodium potassium & ammonium carbonates and hydroxides
   2. all nitrates
   3. Most sulphates
   4. most chlorides bromides and iodides

1. Transfer energy to the surrondings
   1. Normally heat energy
      1. Causes surroundings to get hotter
2. E.g.
   1. Combustion
   2. Oxidisation reactions
   3. Neutralisation

1. Taking energy from the surrondings
2. E.g
   1. reaction between ethanoic acid and sodium carbonate
   2. Electrolysis
   3. Thermal decomposition

1. A reversible reaction is shown by a Equilibrium symbol

   Nota:

   • ⇌ 

1. + pure sample -expensive -unsafe

1. + cheaper + safer - h20 could interfer