Chemistry

• Mass number (bigger) 


  Number of protons and number of neutrons added together
• Atomic mass (smaller)


  Number of protons/neutrons
• Charge 


  Proton = +1

  Neutrons = 0

  Electron = -1
• Relative atomic mass

  Proton = 1

  Neutron = 1

  Electron = 0
• Isotopes

  the same number of protons but different number of neutrons in the nucleus
• nucleon number

  the number of protons and neutrons in the nucleus
• Alkali metals reacting with water

  Lithium - floats, fizzes, becomes smaller until it disappears, purple with universal indicator

  Sodium - melts into a ball and moves around the surface, then fizzes until it disappears

  Potassium - metal melts, floats, moves around very quickly on the surface of the water, self-ignites - which ignites the hydrogen gas, results in sparks and a lilac flame, sometimes a small explosion at the end. Reacts violently

  All 3 float and produce bubbles.
• Halide test - results

  Chloride - white

  Bromide - Creme / off white

  Iodine - yellow colour
• Halide test - method

  1.Dissolve into distilled water

  2. Add 2cm depth of nitric acid

  3. Add silver nitrate drop by drop

  4. If a precipitate forms, record the colour
• If a halide is more reactive than the one it is reacting with, it gets displaced and the more reactive one bonds with the other element.
• Alkali metals - group 1

  Halogens - group 7

  Noble gasses - group 0
• Rates of reactions

  Concentration - more collisions from more particles

  Temperature - Hotter, more energy, move faster, higher chance of successful collision

  Surface area - larger surface area, more space for successful collision

  Pressure - particles are closer, collide more
• Catalyst

  Catalysts speed up the rate of reaction without getting used up. Catalysts are specific to reactions - certain catalysts for certain reactions. They work mostly by lowering the activation energy.
• Treating drinking water

  1.The water passes through a mesh screen to remove big bits like twigs

  2. Chemicals are added to make solids and microbes stick together and fall to the bottom

  3. The water is filtered through gravel beds to remove all the solids

  4. Chlorine is added to the water to sterilise it (chlorine kills remaining harmful microbes)
• Water treatment process

  Screen -> coarse tank -> sedimentation tank -> fine filler -> chlorine added -> storage tank -> to homes and factories
• Arguments FOR fluoride in drinking water

  • Too much fluoride causes luoridosis (ugly brown mottling of the teeth)
  • Fluoride makes your teeth stronger
  • Some people are unable to buy good quality toothpaste
  • Fluoride decreases enamel decay
  • Fluoride can kill bacteria
  • Fluoride is naturally occurring in drinking water
  • Fluoride prevents cavities, especially in children under 12
  • One third of people follow their dentist's advice on tooth brushing
• Arguments AGAINST fluoride in drinking water

  • Fluoride can disrupt some of the enzymes in your body
  • Fluoride is more effective in toothpaste than in water
  • New scientific studies show that very few people benefit from fluoride in drinking water
  • Fluoride appears to cause bone cancer in boys
  • Giving fluoride to pregnant rate can cause holes in the unborn rat's brain
  • Fluoride is naturally occurring in drinking water
• Distillation

  1.Evaporation

  2. Condensation

  3. Collection
• Temporary hardness of water

  Reason: presence of calcium or magnesium hydrogencarbonate in the water

  Solution: Boiling the water - the hydrocarbonates decompose, laving insoluble calcium carbonate or magnesium carbonate - this is the scale found in kettles and boilers.
• Permanent hardness of water

  Reason: presence of calcium or magnesium sulphate in the water

  Solution: soften the water by adding sodium carbonate or by ion exchange.
• Hard water - Advantages


  Hard water tastes better than soft water. Beer production often involves artificially hardening the water.

  Considered to strengthen bones and teeth.

  Helps to reduce heart disease.
• Hard water - Disadvantages

  It produces limescale which 'furs up' appliances, making them less efficient.

  Uses more energy to boil water.

  Reduces the efficiency of kettles, boilers, coffee machines, etc.

  Removing limescale is expensive.

  More soap has to be used, resulting in soap seum in the wash. Modern detergents are used instead of soap in washing machines.
• Mr

  The Ar of the element (atomic mass) X how many atoms there are, then added to the other elements in the chemical.

  Ar of H2O - (2x1)+(1x16) = 2+16 = 18
• Moles

  Moles = mass / Mr

  Calculate the number of moles in 2g of sodium oxide.

  Mr of Na2O = (2x23)+(1x16) = 46+16 = 62

  Moles of Na2O = 2/62 = 0.032 moles.
• Testing for gasses 


  Hydogen - put a lighted splint around the mouth of the test-tube. If hydrogen is present, it will burn with a squeaky pop.

  Oxygen - Put a glowing splint near the mouth of the test-tube. If oxygen is present, it will re-light the glowing splint.

  Carbon dioxide - mix with calcium hydroxide solution. If carbon dioxide is present, it will produce a white precipitate of calcium carbonate, also known as limewater.
• Structure of the earth 


  Inner core Outer core mantle crust

  ) ) ) )
• Plate boundaries 


  Constructive <- ^ -> Land moves apart, magma comes up and . magma l hardens into new land.

  Destructive -> <- Oceanic plate goes under the coastline when . plates are pushed together, because oceanic plates are denser. This creates tsunamis and volcanic eruptions.

  Conservative ^ I l Plates grind together. This creates earthquakes.

  I I v
• Original atmosphere 


  Volcanic activity meant there was lots of CO2.

  Water vapour, released from volcanoes, condensed to form oceans.

  Carbon dioxide gas dissolved into the oceans.

  Green plants and algae used up the CO2 for photosynthesis and turned it into oxygen.

  Animals and other complex life evolved.
• Effects of global warming

  • changing weather patterns
  • flooding
  • melting ice caps
  • loss of habitat
  • changing growth patterns of plants
  • rising sea levels
• Alkali Metals - group 1

  • When they react, they lose an electron from the outer shell​. All the atoms in group 1 have one electron in the outer shell.
  • The reactivity increases down the group​
  • When reacting with oxygen in the air, the metals tarnish​.
• Halogens / halides​ - group 7

  • All kill bacteria​
  • All gain electrons when reacting​
  • Reactivity decreases down table​
  • The more heat is added, the less the reactive it is
  • The silver nitrate test allows us to identify them
• Flame Test

  • Sodium = Yellow​
  • Magnesium = White​
  • Calcium = Brick Red​
  • Barium = Apple Green​
  • Potassium = Lilac​
  • Copper = Green​
  • Lithium = Red​
• Current Atmosphere

  • Nitrogen 78%
  • Oxygen 21%
  • Argon (and other noble gasses) 0.9%
  • Carbon Dioxide 0.04%
• yield percentage = actual yield / theoretical yield X 100