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Chemistry ATP

lisawinkler10 Chemistry GCSE English 5.0Average rating 5.0 out of 5 (2 ratings)

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Chemistry ATP

Precautions
- For poisonous gases (toxicity of gas)
  - Fume cuboard
  - Well ventilated room
    - Prevents burning of a substance
  - e.g. Nitrogen Dioxide, Ammonia, Bromine
- Repeat and take averages
- Wear goggles, lab coat and tie hair back
- When heating alcohol, a water bath should be used because fire will be produced if touched by a lighted splint
Common Variables
- Concentration
- Volume
- Surface Area
- Mass
- Temperature
Exam Technique
- Independent variable (the one you change) goes on x-axis and the dependent on y-axis
- For manufacturing errors, look carefully at apparatus (e.g. burettes without taps)
- Don't round values in titration or mole questions
Tests
- For water
  - Add anhydrous Copper(II) Sulphate (white to blue)
  - Add anhydrous Cobalt(II) Chloride (blue to pink)
- For alkenes and alkanes
  - Alkenes: Add (if liquid) or pass through (if gas) bromine water and shake (brown to colourless)
  - Alkanes: (remain orange/brown)
- For purity of substance
  - Test melting/boiling point and compare to correct value
- Cation/Anion Tests (link)
  - Chemistry ATP Tests
- For hydrochloric acid
  - Add silver nitrate (white ppt. formed)
Gas Collection
- Upward delivery
  - Gases less dense than air
  - e.g. Hydrogen, Ammonia
- Downward delivery
  - Gases more dense than air
  - e.g. Carbon Dioxide
- Displacement of water method
  - Insoluble gases
  - e.g. Methane
Experiments
- Crystallisation
  - Heat till point of crystallisation, allow to cool slowly, filter and dry
    - Place a stirring rod in solution and if crystals form on it, it's the point of crystallisation
  - Crystallisation is the formation of solid crystals of a substance by precipitating it out from a staurated solution
- Fermentation
  - Glucose and yeast used (yeast contains enzymes)
    - 37 degrees is optimum for enzymes
    - Reaction might stop due to an excess in conc. of alcohol, the yeast dies or Glucose finishes up
  - Bung is used to let Carbon Dioxide out and prevent entry of Oxygen
    - Oxygen would oxidise the alcohol to Carboxylic Acid and affect anaerobic respiration
- Chromotography
  - Spray locating agent if colourless dye (such as amino acids and sugars)
    - RF = distance moved by dye/distance moved by solvent
- Electrolysis
  - Concentration promotes the discharge of ions further down the reactivity series because their compounds are stable
  - Suitable electrodes: Graphite/Carbon/Steel
- If on heating condensation occurs, the solid is hydrated
Agents
- Oxidising
  - Acidified Potassium Manganate(VII) (purple to colourless)
  - Acidified Potassium Dichromate(VI) (orange to green)
- Reducing
  - All metals (mention Group 1 when asked)
  - Aqueous Potassium Iodide (colourless to brown)
  - Sulphur Dioxide
- Drying
  - Concentrated Sulphuric Acid (all gases except Ammonia)
  - Calcium Oxide (for Ammonia and neutral gases)
  - Anhydrous Calcium Chloride (all gases except Ammonia)
- Locating
  - Ninhydrin
Universal Indicators
- Methyl orange (red, orange, yellow)
- Phenolphtalein (colourless, pink)
- Bromothymol (yellow, dark green, blue)
Apparatus
- Condenser
  - To liquify vapour in distillation and returning unreacted vapour back to the solution
- Glass beads
  - To cool the gases in fractional distillation by absorbing heat from them
- Fractionating column
  - To separate various liquids using their boiling points
- Safety bulb
  - In pipettes to prevent liquid from entering mouth
- Cover ethanol with a lid because it's volatile
- Crush a solid to increase surface area (use a pestle and mortar)
- Purpose of mineral wool is to absorb and hold liquid
Colours
- Metals
  - Zinc is a grey solid (white compounds)
  - Lead is a shiny bluish metal
  - Iron is a shiny blackish solid
    - Iron (II) salts are grey-green. Iron (III) salts are reddish-brown.
  - Group 1, 2 metals are white/silvery white
  - Group 3 metals are shiny grey
  - Copper is a pinkish solid
    - Copper(II) sulphate/hydroxide/nitrate are blue. Copper(II) chloride/carbonate are green.
- Non-metals
  - Iodine is a black solid
    - Its vapours are purple. Silver iodide and Lead iodide are yellow.
  - Chlorine is a green gas
    - Silver chloride and Lead chloride are white
  - Bromine is a red-brown gas
    - Silver bromide and Lead bromide are cream
  - Nitrogen dioxide is a brown gas.
  - Sulphur and Phosphorus are yellow solids
Important reactions
- Metal + Water → Metal hydroxide + Hydrogen Metal + Acid → Salt + Hydrogen
- Acid + Carbonate → Salt + Water + Carbon Dioxide
- Acid + Base → Salt + Water
- Metal Hydroxide + Ammonia Salts → Salt + Ammonia + Water
- Acidic Oxide + Water → Acid Neutral Oxide + Air → Acid Basic Oxide + Acid → Salt + Water
- Alkene + Steam → Alcohol
- Glucose + Yeast → Ethanol + Carbon Dioxide
- Acid + Alcohol → Ester + Water
- Alcohol (when oxidised) → Organic Acids + Water
- Potassium, Sodium, Calcium, react with water to form hydroxides and metals below (till Copper) react with steam to form metal oxides
- Water and oxygen is needed for rusting - water level increases as oxygen is used up
- Copper oxide and hydrogen make copper (black to brown)
Acids and Bases
- A concentrated acid contains a large number of H+, hydrogen ions and a concentrated base contains a large number of OH-, hydroxide ions
- A strong acid ionizes completely giving H+ in solutions and a strong base ionizes completely gived OH- in solutions