Key things

• Paper Chromatography

  It includes:

  1. A beaker
  2. Water
  3. Pencil
  4. Ink (which you wish to seperate)
  5. Filter Paper
  6. Piece of wood and a pin (or anything to keep the paper from falling into the water!)
• Paper Chromatography Experiment


  How to carry out the experiment:

  1. Draw a straight, horizontal pencil line about 1cm from the bottom of the filter paper (we use pencil since it does not dissolve in water).
  2. Draw a spot of ink on the pencil line.
  3. Secure the filter paper so that the bottom is in the water, making sure that the water doesn’t touch the ink spot.
  4. You will see the water soak up the paper and drag the ink with it.
  5. Before the water soaks to the very top of the paper, take the paper out and draw a pencil line at the point the water has reached.
• Chromatography

  NOTE: The highest point the water reaches is called the solvent front.

  NOTE: Lots of different solvents can be used instead of water, it really depends on the type of ink you are using.

  Interpreting Chromatograms

  On most chromatograms, the number of spots at the end of the experiment usually shows how many dyes were in the ink dot. Although, sometimes there may be more than one type of dye in a spot. So remember, there are at least as many substances in a mixture as there are spots on the chromatogram.
• evaporation and crystallisation

  Filtration:

  Separating insoluble solids from a liquid.

  This simply done by using filter paper, a filter funnel and a beaker (to catch the liquid)! 

  Evaporation:

  Separating soluble solids from a liquid. Evaporation is when you heat a liquid up enough that it turns into a gas.

  1. Set up the equipment on top of a heat proof mat, as seen above.
  2. Turn the bunsen burner onto a blue flame.
  3. Wait until all of the liquid has evaporated and there is only solid left. Make sure you don’t let the liquid get hot enough to spit, this would hurt if it got you!
• evaporation and crystallisation

  Crystallisation

  1. Separating What evaporation is and how it is used to separate substances.
  2. What filtration is and how it is used to separate substances
  3. How to separate soluble and insoluble solids from a liquid.
  4. How to form crystals when separating a soluble solid from a liquid
  5. s from a liquid and making lovely crystals! Crystallisation is much slower than evaporation, but the technique is very similar.
• Crystallisation


  Here is how to crystallise soluble solids from a liquid: __

  1. Set up the equipment on top of a heat proof mat, as seen above.
  2. Slowly heat the solution on a low flame.
  3. Once some of the solvent has evaporated, or when you see crystals starting to form, carefully move the bunsen burner from the evaporating dish.
  4. Allow the dish to cool.
  5. You should see more crystals gradually forming as the liquid cools.
  6. Once it is completely cool, filter the crystals out of the solution.
  7. Allow the crystals to dry in a warm place.
• Distillation

  1. A mixture of two liquids is heated up to the lowest of the two boiling points.
  2. One of the liquids evaporates into a gas.
  3. The gas drifts into the condenser, where it is cooled.
  4. The gas turns back into a liquid (condenses) and drips down into the beaker on the other side.
  5. If the temperature doesn’t reach the second boiling point, the two liquids will be separated between the two beakers.
• Fractional distillation

  • This is used to separate two or more liquids that are miscible with one another (e.g., ethanol and water from a mixture of the two)
  • The solution is heated to the temperature of the substance with the lowest boiling point
  • This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker
  • All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture
• Filtration


  Removes large insoluble particles by passing the water through layers of sand and gravel filters that trap larger particles
• Filtration


  • Wire mesh filters are sometimes used, depending on the level of impurities in the water
• Sedimentation


  Large insoluble particles sink to the bottom of a tank of water that has been left still for some time
• Sedimentation


  • Iron sulfate or aluminium sulfate is sometimes added to help the fine particles clump together
• Chlorination


  This process is used to kill bacteria and microorganisms which are too small to be trapped by the filters
• Bacterial diseases


  • Cholera
  • Typhoid
• These bacterial diseases can arise by the consumption of untreated water
• Making Water Potable

  • Ground water from aquifers is relatively clean but surface water (from rivers & lakes) and waste water need significant treatment in order to be fit for human consumption
  • Untreated water contains soluble and insolubleimpurities
  • Insoluble impurities include soil, pieces of plants and other organic matter and soluble impurities include calcium, metallic compounds and inorganicpollutants
  • Unclean water also contains microbes which can cause illness
  • Potable water means water that is clean enough for human consumption
• Core Practical: Investigating pH

  • Use a pipette to measure a fixed volume of dilute HCl into a conical flask
  • Add one spatula of calcium oxide or calcium hydroxide to the flask and swirl
  • When all the base has reacted record the pH of the solution
  • If using U.I. paper use the glass rod to extract a sample from the flask
  • Repeat for different numbers of spatula (1-10) of solid but the same volume of HCl
  • Record your results neatly in table format
• Core Practical: Investigating pH

  Hazards:

  • Copper(II) oxide can cause serious eye irritation and is a skin irritant. It is harmful if swallowed or inhaled and is toxic to aquatic life
  • Dilute hydrochloric acid is not classified as hazardous at the concentrations typically used in this practical, however it may still cause harm to the eyes or the skin
  • For both substances, avoid contact with the skin and use safety goggles
  • For copper(II) oxide, care should be taken not to inhale the powder
• Preparing Copper Sulfate


  1. Add 50 cm3 dilute acid into a beaker and warm gently using a Bunsen burner

  2. Add the copper(II) oxide slowly to the hot dilute acid and stir until the base is in excess (i.e. until the base stops dissolving and a suspension of the base forms in the acid)

  3. Filter the mixture into an evaporating basin to remove the excess base

  4. Gently heat the solution in a water bath or with an electric heater to evaporate the water and to make the solution saturated

  5. Check the solution is saturated by dipping a cold glass rod into the solution and seeing if crystals form on the end

  6. Leave the filtrate in a warm place to dry and crystallise

  7. Decant excess solution and allow the crystals to dry
• The Haber Process


  1. H2 and N2 obtained from natural gas and air respectively, pumped into compressor

  2. Gases compressed to 200 atmospheres

  3. Pressurised gases pumped into tank with catalytic iron beds at 450°C, reaction to form ammonia

  4. Unreacted H2 and N2, and ammonia product pass to cooling tank, ammonia liquefied and stored, unreacted gases recycled back into system
• N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
• Conditions for Haber process

  higher temperature would favour the reverse reaction as it is endothermic (takes in heat) so a higher yield of reactants would be made

  lower temperature is used it favours the forward reaction as it is exothermic (releases heat) so a higher yield of products will be made
• Conditions for haber process: pressure

  200 atm

  • lower pressure would favour the reverse reaction as the system will try to increase the pressure by creating more molecules (4 molecules of gaseous reactants) so a higher yield of reactants will be made
  • A higher pressure would favour the forward reaction as it will try to decrease the pressure by creating less molecules (2 molecules of gaseous products) so a higher yield of products will be made (expensive+dangerous)
• Conditions for Haber process: Catalyst

  catalyst of iron is used to speed up the reaction
• The reaction conditions chosen for the Haber process are not ideal in terms of the yield but do provide balance between product yield, reaction rate and production cost. These are called compromise conditions as they are chosen to give a good compromise between the yield, rate and cost.
• Effect of Temperature Changes on an Equilibrium Table

  Increase in temperature- equilibrium moves I the endothermic direction to reverse the change.

  Decrease in temperature- equilibrium moves in the exothermic direction to reverse the change
• Effects of changes in pressure

  Increase in pressure - equilibrium shifts in the direction that produces the smaller number of molecules of gas to decrease pressure again

  Decrease in pressure - equilibrium shifts in the direction that produces the larger number of molecules of gas to increase the pressure again
• Effect of concentration on Equilibrium

  Increase in concentration - equilibrium shifts to the right to reduce the effect of increasing concentration of the reactant

  Decrease in concentration- Equilibrium shifts to the left to reduce the effect of a decrease in reactant for an increase in the concentration of product
• 4 factors of life cycle assessment 


  Raw materials

  manufacture

  usage

  disposal
• Bioleaching


  A technique that makes use of bacteria to extract metals from metal ores
• Bacteria used in bioleaching

  • They are capable of breaking down ores to form acidic solutions containing metal ions such as copper(II)
• Leachate


  The solution containing significant quantities of metal ions
• Extracting metals from leachate

  1. Reducing metal ions to solid metal form

  2. Extracting by displacement reactions or electrolysis
• Metals extracted by bioleaching

  • Copper(II) sulfide
  • Iron(II) sulfide
• Bioleaching does not require high temperatures
• Bioleaching produces toxic substances which need to be treated so they don't contaminate the environment
• Bioleaching is used for primary extraction of metals and mining waste clean up operations
• Phytomining


  • This process takes advantage of how some plants absorb metals through their roots
  • The plants are grown in areas known to contain metals of interest in the soil
  • As the plants grow the metals are taken up through the plants vascular system and become concentrated in specific parts such as their shoots and leaves
  • These parts of the plant are harvested, dried and burned
  • The resulting ash contains metal compounds from which the useful metals can be extracted by displacement reactions or electrolysis
• Phytoextraction and bioleaching are principally used for copper extraction due to the high global demand for copper, but these methods can be applied to other metals.
• Prepare a Salt by Titration


  1. Use a pipette to measure the alkali into a conical flask and add a few drops of indicator (phenolphthalein or methyl orange)

  2. Add the acid into the burette and note the starting volume

  3. Add the acid very slowly from the burette to the conical flask until the indicator changes to appropriate colour

  4. Note and record the final volume of acid in burette and calculate the volume of acid added (starting volume of acid - final volume of acid)

  5. Add this same volume of acid into the same volume of alkali without the indicator

  6. Heat to partially evaporate, leaving a saturated solution

  7. Leave to crystallise decant excess solution and allow crystals to dry