Chemistry

• Acids


  Have lower pH than 7
• Bases


  Have higher pH than 7
• Indicators


  Substances which change colour when you add acid or alkali
• pH meter


  Measures pH more specifically
• Type of ion in acids

  H+ (hydrogen)
• Type of ion in bases

  OH- (hydroxide)
• pH of neutral is 7, acids are less than 7, alkalis are greater than 7
• Litmus turns red in acid, blue in alkali</b>
• Methyl orange turns yellow in acid, red in alkali
• Phenolphthalein is colourless in acid, pink in alkali
• Increasing H+ concentration in acidic solution

  Decreases the pH
• Universal indicator


  Measures pH from 0 to 14, made from dyes
• Increasing H+ concentration


  Increases the number of H+ particles
• Concentrated


  More solute dissolved in a given volume
• Alkali


  Soluble base
• Base


  Any substance that reacts with an acid to form a salt and water
• General equation for reaction between acids and metals

  Acid + metal oxide → salt + water
• General equation for reaction between acids and metal hydroxides

  Acid + metal hydroxide → salt + water
• Test for hydrogen


  • Squeaky pop with a lighted splint
• Test for carbon dioxide

  • Turns limewater milky white
• Neutralisation reaction


  Reaction between a base and an acid
• Titration experiment


  1. Known volume of alkali, add indicator

  2. Fill burette with acid

  3. Add acid to alkali until indicator shows neutral solution

  4. Repeat
• Preparing a pure dry sample of an insoluble salt


  1. Mix solutions of soluble salts

  2. Insoluble salt forms a precipitate

  3. Filter off precipitate

  4. Wash several times with pure water

  5. Dry in an oven
• Moles = mass / Mr
• Number of atoms = number of moles x (6.02 x 10^23)
• 16g of oxygen molecules (O2) contains 0.5 moles, which is 3.01 x 10^23 molecules
• Ionic bond


  Transfer of electrons between atoms
• Cation


  Ion with a positive charge
• Anion


  Ion with a negative charge
• Covalent bond


  Sharing of electrons between atoms
• Substances with covalent bonds


  • Simple molecular substances, giant covalent structures, polymers
• Covalent bonds


  • Strong, require a lot of energy to break
• Metals form ionic bonds, non-metals form covalent bonds
• Ionic compounds have high melting and boiling points, don't conduct electricity
• Simple molecular substances have low melting and boiling points, don't conduct electricity
• Giant covalent structures like diamond and graphite are very hard and have high melting points
• Graphite has delocalised electrons which allow it to conduct electricity
• Paper chromatography


  1. Distance travelled by solute

  2. Distance travelled by solvent

  3. Compare distances
• Distance travelled by solute


  Distance Howelled by solute of each spot
• Distance travelled by solvent

  Distance travelled by the solvent