chemical changes (4)

• metals + oxygen -->

  metal oxides
• reduction (in terms of oxygen)

  the loss of oxygen
• oxidation (in terms of oxygen)

  the gain of oxygen
• a more reactive metal will displace a less reactive metal from its compound
• when metal reacts with other metal substances they form positive ions
• reduction (in terms of electrons)

  the gain of electrons
• oxidation (in terms of electrons)


  the loss of electrons
• each side of an ionic equation should add up to the same number
• acid + metal --> salt + hydrogen
• acids are neutralised by alkalis and bases to form water and a salt
• acids are neutralised by metal carbonates to produce salts, water and carbon dioxide
• how to make soluble salts 


  add the chosen solid insoluble substance to the acid then the solid will dissolve, keep adding acid until it is in excess, filter out the excess solid leaving out the salt solution, leave to evaporate and crystals will form
• acids produce what type of ions in an aqueous solution

  H+
• alkalis produce what type of ions in aqueous solutions

  OH-
• How to carry out a titration

  1. Wash burette using dilute hydrochloric acid and then water

  2. Fill burette to 100cm3 with acid with the meniscus' base on the 100cm3 line

  3. Use 25cm3 pipette to add 25cm3 of alkali into a conical flask, drawing alkali into the pipette using a pipette filler

  4. Add a few drops of a suitable indicator to the conical flask

  5. Add acid from burette to alkali until end-point is reached

  6. The titre is the difference between​ ​the​ ​first​ ​(100cm3​ )​ ​​and​ ​second​ ​readings​ ​on​ ​the​ ​burette

  7. repeat the experiment to gain more precise results
• Titre


  The volume of acid needed to exactly neutralise the acid
• strong acid


  completely ionised in aqueous solution
• weak acid


  partially ionised in aqueous solution
• the stronger the acid the lower the pH
• where do positively charged ions move to in electrolysis 


  the negative electrode - cathode
• where do negatively charged ions move to in electrolysis

  the positive electrode - anode
• Metals​ ​that​ ​are​ ​more​ ​reactive​ ​than​ ​carbon​,​ ​so​ ​too​ ​reactive​ ​to​ ​beextracted​ ​by​ ​reduction​ ​with​ ​carbon,​ ​​​are​ ​extracted​ ​by​ ​electrolysis​ ​of​ ​moltencompounds.