Chemical Changes

• When a metal reacts with oxygen they form metal oxide.
• Oxidation reaction is when oxygen is gained in a reaction.
• Reduction reaction is losing oxygen in a reaction.
• Metal + Water -> Metal Hydroxide + Hydrogen
• The reactivity series is:

  Potassium

  Sodium

  Lithium

  Calcium

  Magnesium

  Carbon

  Zinc

  Iron

  Hydrogen

  Copper
• When metals react, they lose electrons and forms a positive ion.
• A more reactive metal will displace a less reactive element from a compound.
• Oxidation is the loss of electrons.
• Reduction is the gain of electrons.
• (aq) mean aqueous solution, dissolved in water.
• Hydrochloric acid - HCl(aq)
• Sulfuric acid H2SO4 (aq)
• Nitric acid - HNO3(aq)
• In aqueous solutions, acids produce hydrogen ions (H+).
• Bases are chemicals which can neutralise acids producing a salt and water.
• Bases which are soluble in water are called alkalis.
• In aqueous solution, alkalis produce hydroxide ions (OH-).
• The pH scale tells us the acidity or alkalinity of a solution.
• Acids have a pH of less than 7.
• Solutions with a pH of 7 are neutral.
• Alkaline solutions have a pH between 8 and 14.
• A pH probe determines the pH electronically.
• A universal indicator changes colour depending if it is acid alkaline or neutral.
• Acid + Metal -> Salt + Hydrogen
• Hydrochloric acids produce salts ending with -chloride.
• Sulfuric acid produces salts ending with sulfate.
• Magnesium reacts rapidly with acids.
• When we react an acid with either a base or an alkali, we make a salt and water.
• Salts contain a positive ion which comes from the base or alkali.
• Salts contain a negative ion which comes from the acid.
• When acids react with a metal carbonate, they make a salt, water and carbon dioxide.
• In aqueous solutions, acid molecules ionise (split) and release H+.
• Strong acids fully ionise in aqueous solutions.
• Hydrochloric acids, sulfuric acids and nitric acids are all examples of strong acids.
• Weak acids partially ionise in aqueous solutions.
• A reversible arrow means that some of the molecule ionise but not all of them.
• Carbonic acid, ethanoic acid and citric acids are all examples of weak acids.
• The pH scales gives us an idea of the concentration of hydrogen ions (H+)
• Ionise means to lose electrons to become positively charged ions.
• The concentration of an acid tells us the amount of acid molecules in a given volume of solution.