Chemistry

• the more acidic, the higher the pH value, the lower the pH value, the lower the acidity
• Using copper(II) sulfate

  • Anhydrous copper(II) sulfate turns white to blue on the addition of water
  • Anhydrous copper(II) sulfate + water → hydrated copper(II) sulfate
  • CuSO4 + 5H2O → CuSO4.5H2O
• Using cobalt(II) chloride:

  • Turns blue → pink on the addition of water, using cobalt chloride paper
  • Anhydrous cobalt(II) chloride + water → hydrated cobalt(II) chloride

  CoCl2 + 6H2O → CoCl2.6H2O
• Solid: The particles in the solid vibrate in their positions, the hotter it becomes the more they vibrate.

  Liquid: The particles move in constant motion and the hotter it gets, faster the particles move and expand slightly.

  Gas: the particles can move freely and far apart, they also move in straight lines. They move in a random motion and the hotter it gets the faster they move. When it is heated it expands and increases pressure.
• Elements: substances that cannot be chemically separated into simpler substances

  Compound: a pure substance made from two or more elements chemically combined together

  Mixture: a substance that can be physically separated, made of different elements and/or compounds
• Solute: the substance that dissolves in a solvent to produce a homogeneous mixture

  Solvent: the substance in which a solute is dissolved to produce a homogeneous mixture mixture

  Concentration: how many particles per volume/weight of substance e.g. 2 grams of iron in 50 grams of cereal
• • Evaporation - to collect solute
  • Crystallisation - to collect bigger solute
  • Paper chromatography : ink/colour
  • Filtration: separation of solvent and solute 
  • Fractional distillation: heat up, cool down, and condense, separate two solvents
• Ions are charged substances that formed through the gain or loss of electrons, cations → loss, anions → gain 
• 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% CO + small amounts of water vapour and other noble gases
• • Noble gases are unreactive (inert) and monatomic gases. 
  • Has a full outer shell → not giving out or gain electrons
•  as a product of complete combustion of carbon-containing substances

  • During complete combustion carbon and hydrogen combine with oxygen to produce carbon dioxide and water → excess oxygen present in this reaction
• as a product of respiration

  • Aerobic respiration takes place in the mitochondria and requires oxygen and glucose, and produces carbon dioxide, water, and energy
  • C6H12O6 + 6O2 → 6CO2 + 6H2O 
  • Glucose + oxygen → carbon dioxide + water 
• – as a product of the reaction between an acid and a carbonate

  • Acid + metal carbonate → salt(carbonate) + carbon dioxide + water
  • Hydrochloric acid HCl → _Chloride
  • Sulfuric acid H2SO4 → _Sulfate
  • Nitric acid HNO3 → _Nitrate
  • Phosphoric acid H3PO4 → _Phosphate
• as a product of thermal decomposition of calcium carbonate

  • Calcium carbonate → carbon dioxide + calcium carbonate
  • Metal carbonate → carbon dioxide + metal carbonate
• Filtration (mesh)

  Passing the water through a wire mesh to remove larger pieces of material e.g. floating sticks and twigs
• Filtration (sand and gravel beds)

  Passing the water through sand and gravel filter beds to remove the suspended solid bits e.g. finer insoluble soil/rock particles and the clear water can be drained off
• Sterilisation


  Sterilising agents are used including adding small amounts of chlorine (Cl2) or ozone (O3) or irradiating with powerful ultraviolet light (UV), all capable of killing harmful microbes
• Extra treatments

  • Addition of fluoride salts
• • Most is been released due to burning of fossil fuels eg coal, natural gas or oil are contaminated with sulfur → burning sulfur in oxygen produce sulfur dioxide: S + O2 → SO2
  • Flue gas desulfurisers are used to prevent emission to sulfur dioxide

  Oxides of nitrogen eg NO2 are also released and when these gases dissolve in rainwater it produced acid rain
• Acid rain effects include:

  • Acid rain leaches aluminium from the soil. That aluminium may be harmful to plants as well as animals. This aluminium ion can damage the gills of fish leading them to die
  • Acid rain also removes minerals and nutrients from the soil that trees need to grow.
  • Limestone buildings and statues are worn away
  • Al³⁺ ions are also leached out from clay as aluminium sulfate which damages tree roots therefore preventing the roots to take up water.
• Other gases

  • Nitrogen dioxide causes acid rain and can combine in hot weather to cause photochemical smog. This contains low-level ozone and is likely to cause breathing problems, especially in people with asthma
  • Carbon monoxide is a highly toxic gas that combines with haemoglobin in blood to stop taking up oxygen - can cause dizziness and headaches and in large amounts death