Chemical Changes

• Acids


  have a pH <7

  turn UI red, orange or yellow

  form solutions containing $H^+$ ions
• Alkalis


  pH >7

  turn UI blue or purple

  form solutions containing $OH^-$ ions
• What does dissociates mean?

  Separates or breaks apart
• What does an acid dissociate into?

  $H^+$$\ ions$
• What does an alkali dissociate into?

  $OH^-\ ions$
• What is a strong acid?

  An acid that completely dissociates in water to produce hydrogen ions.
• What is a weak acid?

  An acid that only partially dissociates in water and has a low concentration of hydrogen ions.
• Acid + metal $\rightarrow$ ?


  Salt + hydrogen
• Acid + metal oxide $\rightarrow$ ?


  Salt + water
• Acid + metal carbonate $\rightarrow$ ?


  Salt + water + carbon dioxide
• Acid + alkali $\rightarrow$ ?


  Salt + water
• What ion is this? $NH_4^+$


  Ammonium
• What ion is this? $OH^-$


  Hydroxide
• What ion is this? $NO_3^-$


  Nitrate
• What ion is this? $SO_4^{2-}$


  Sulfate
• What ion is this? $S^{2-}$


  Sulfide
• What ion is this? $CO_3^{2-}$


  Carbonate
• What ion is this? $CO_3^{2-}$


  Carbonate
• What is oxidation?

  Oxidation is loss of electrons
• What is reduction?

  Reduction is gain of electrons
• What is OIL RIG?

  OIL RIG stands for Oxidation Is Loss, Reduction Is Gain. It is a mnemonic used to remember the process of oxidation and reduction in chemical reactions.
• What is a redox reaction?

  A redox reaction is a reaction where both oxidation and reduction occur
• What is a displacement reaction?

  A chemical reaction where one element or ion is replaced by another element or ion in a compound.
• Which way does the reactivity increase in the alkali metals?

  Down the group
• Which way does reactivity increase in the halogens?

  Up the group
• What is electrolysis?

  An ionic compound conducts electricity when molten or in solution. The current causes the ionic compound to split up and form new substances.
• What are some uses of electrolysis?

  • purifying copper
  • plating metals with silver or gold
  • extracting reactive metals e.g aluminium
  • making chlorine, hydrogen, and sodium hydroxide
• What is the cathode?

  The negatively charged electrode where reduction occurs
• What is the anode?

  The positively charged electrode where oxidation takes place
• What are cations?

  Positively charged ions.
• What are anions?

  Negatively charged ions.
• What are the half equations for $Al_2O_3$?


  Al$^{3+}$+ 3e$^-$$\rightarrow$ Al

  2O$^{2-}$$\rightarrow$ O$_2$+ 4e$^-$
• The boiling point of aluminium oxide (alumina) is very high so it is mixed with another substance. What is this substance?

  Cryolite
• What is alumina extracted from?

  Bauxite ore
• Where does the highest cost proportion of the electrolysis of aluminium oxide come from?

  The amount of energy needed to keep the mixture molten