C5 GCSE mindmap

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  • C5-Chemical Changes
    • Reactivity
      • Reactivity is a measure of how easily a substance will react
      • Pandas, Steal, Little, Cats, Making, Crazy, Zoos, In, Hot, Countries.
        • Potassium, Sodium, Lithium, Calcium, Magnesium, Carbon, Zinc, Iron, Hydrogen, Copper
      • The more reactive the metal is the faster the reaction will be. This can also be measured as more bubbles are formed every minute(rate).
        • And also the more reactive the metal is the greater the temperature change will be.
      • Displacement
        • A more reactive metal takes the place (displaces) a less reactive metal from its compound/ from an aqueous solution of one of its salts
    • Reactions of metals with water
      • Metal+water = Metal hydroxide+ hydrogen
        • Sodium+ water = Sodium hydroxide + Hydrogen
    • Dilute acids
      • Metals also react with dilute acids
      • Metal+Acid= Salt+ Hydrogen
        • The salt has two words. The first word is the metal e.g. sodium, and the second word is the acid e.g. sulfate or nitrate or chloride
        • Metal reactant is insoluble whereas the salt produced is soluble.
    • Metal ores
      • Metals are found in the earths crust and most are chemically combined with other elements like oxygen or sulfur
        • This means they need to be extracted to get the pure metals
      • Metal compounds formed underground are called ores; ores are usually metal oxides
        • Extracting metals
          • Metals within metal ores that are less reactive than carbon can be extracted from their ores in a displacement with carbon
            • e.g. lead oxide + carbon = lead + carbon dioxide
              • Carbon is a black powder but after the reaction the orange copper can be clearly seen in the black powder
            • Metals that are more reactive than carbon are extracted through the process of electrolysis
            • Tungsten is extracted by using hydrogen because it produces a very pure metal
              • e.g. tungsten oxide + hydrogen =     tungsten+ water (steam)
            • Example of reduction e.g. if oxygen was lost from copperoxide
    • Redox reactions
      • Acids are substances which form a H+ ion when in solution
        • Examples are: Hydrochloric acid(HCl), Sulfuric acid(H2SO4) and Nitric acid(HNO3)
      • Oxidation is the gain of oxygen but loss of electrons
        • Half equation: Fe(s)=Fe2+(aq)+2e-
          • Ionic equation: Fe(s)+Cu2 (aq)=Fe2+(aq)+Cu(s)
            • Half equation: Cu2+(aq)+2e-=Cu(s)
      • Reduction is the loss of oxygen but gain of electrons
        • Half equation: Cu2+(aq)+2e-=Cu(s)
      • Species is an ion, atom or group of ions/atoms
      • Mg(s)+H2SO4(aq)=MgSO4(aq)+H2(g)
        • Mg is oxidised. Hydrogen is reduced. Sulfuric acid is the spectator ion (it doesn't take part in the reaction)
    • Acids and bases
      • The higher the concentration of H+ ions, the stronger the acid is
        • A strong acid is completely ionised in aqueous solution
          • A weak acid is only partially ionised in aqueous solution
            • Ethanoic acid, citric acid, carbonic acid
              • Acids give off H+ ions whereas alkaline give of OH- ions
                • When you reduce/dilute a H+ substance (acid) by a factor of 10, its pH unit goes up by one: becomes less acidic
      • Neutralisation reaction
        • Acid+Base = salt+water
          • acid +metal carbonate = salt+water+ carbon dioxide
            • This is called a neutralisation reaction because the products are always neutral
            • H+(aq)+OH-(aq)=H20(l)
    • PRACTICAL: obtaining a dry, pure copper salt
      • How to make copper sulfate crystals from copper(II) oxide and sulfuric acid
        • Sulfuric acid+copper (II)oxide = copper (II)sulfate+ water
          • H2SO4(aq)+ CuO(s)+ CuSO4(aq)+ H20(l)
      • 1. Add insoluble copper oxide UNTIL IN EXCESS to sulfuric acid and stir. WARM GENTLY on tripod and gauze. DO NOT BOIL.
        • 2.The solution turns blue as reaction occurs. Excess copper oxide can be seen.
          • 3. When no more copper oxide reacts (reaction is complete), filter out solution to remove excess copper oxide
            • 4.Set up apparatus for crystallisation and perform crystallisation until you get dry crystals.
    • PH Scale
      • To test pH, you can use:   pH sensor, pH Probe attached to a pH metre, an indicator
        • 0-6=acid, 7=neutral, 8-14=alkaline
          • pH7,pH values more than 7 are alkaline
          • Obtaining a pH curve
            • pH7,pH values more than 7 are alkaline
            • 1. Collect 20cm3 of sodium hydroxide in a beaker and measure its pH using a pH sensor.          2. Add acid using burette, 1cm3 at atime and measure pH of solution in beaker

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