4th Sep '25

Schemes of Work

C2
- C2.3
  - Lesson 01 - How can we identify the purity of a substance? Lesson Plan Lesson Title
    - In chemistry, a pure substance is a single element or compound, not mixed with any other substance.
      - Suggested Activity:
        Design a flow chart assigning elements/compounds/mixtures as pure or impure.
        Why is 'pure' orange juice not pure?
    - A formulation is a mixture that has been designed as a useful product.
      - Suggested Activity:
        Case study: How tablets are made to ensure that the taker receives the correct dose of medication.
    - Pure elements and compounds melt and boil at specific temperatures. Melting point and boiling point data can be used to distinguish pure substances from mixtures.
      - Suggested Activity:
        Study a range of melting points of pure and impure substances. Students draw conclusions from this.
    - Formulations include fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods.
      - Suggested Activity:
        Study a recipe and discuss how changing the recipe may affect the food product made. Link to formulations and why we use formulations
    - In everyday language, a pure substance can mean a substance that has had nothing added to it, so it is unadulterated and in its natural state, eg pure milk.
    - Formulations are made by mixing the components in carefully measured quantities to ensure that the product has the required properties.
      - Suggested Activity:
        Suggested practical:
        Making mayonnaise
        Equipment Required:
        Making mayonnaise
        
        Per group:
        •Small screw top bottles (100 cm3) or test tubes and bungs
        • Pipettes
        • Teaspoons (or disposable plastic spoons)
        • Cooking oil
        • Washing up liquid
        • Sugar
        • Flour
        • Mustard powder
        • Egg
        • 2 bowls (or 100 cm3 glass beakers)
        • Egg yolk separator
        •Plastic disposable gloves
    - Students should be able to use melting point and boiling point data to distinguish pure from impure substances.
      - Suggested Activity:
        Analyse information on the melting points of pure gold against counterfeits as a method for determining purity
    - Students should be able to identify formulations given appropriate information.
  - Lesson 02 - How can we use chemical tests to identify an unknown gas? Lesson Plan Lesson Title
    - The test for carbon dioxide uses an aqueous solution of calcium hydroxide (lime water). When carbon dioxide is shaken with or bubbled through limewater the limewater turns milky (cloudy).
      - Suggested Activity:
        Practical: Testing for different gases
        - Hydrogen
        - Carbon dioxide
        - Oxygen
        - Chlorine
        
        Students to plan and investigate the gas tests
        Equipment Required:
        Practical: Testing for different gases
        Prepared samples of:
        - Hydrogen
        - Oxygen
        - Chlorine
        
        Equipment to prepare Carbon dioxide:
        -Marble chips
        -Hydrochloric acid
        -Delivery tubes
        -Conical flasks
    - Students do not need to know the names of components in proprietary products.
    - The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound
    - The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.
    - The test for oxygen uses a glowing splint inserted into a test tube of the gas. The splint relights in oxygen
  - Lesson 03 - How can we use paper chromatography to identify an unknown mixture? Lesson Plan Lesson Title
    - Chromatography can be used to separate mixtures and can give information to help identify substances.
    - Chromatography involves a stationary phase and a mobile phase.
    - Separation depends on the distribution of substances between the phases
      - Suggested Activity:
        Watch video of cars racing down runway (attached on ppt on shared drive). Thinking point - Why did the cars cross the line at different times?
    - The ratio of the distance moved by a compound (centre of spot from origin) to the distance moved by the solvent can be expressed as its R value
    - RT = distance moved by substance / distance moved by solvent
    - Different compounds have different R values in different solvents,
      - Suggested Activity:
        Students use mock chromatograms to calculate Rf values and identify unknown substance. Spice it up as a ransom note.
    - Rf values can be used to help identify the compounds.
    - The compounds in a mixture may separate into different spots depending on the solvent but a pure compound will produce a single spot in all solvents.
    - Students should be able to explain how paper chromatography separates mixtures
      - Suggested Activity:
        Research where chromatography is used in forensics - Inks, colourings, dyes, drugs etc
    - Students should be able to suggest how chromatographic methods can be used for distinguishing pure substances from impure substances
    - Students should be able to interpret chromatograms and determine R values from
      chromatograms
    - provide answers to an appropriate number of significant figures. (MS)
    - Elements and compounds can be detected and identified using instrumental methods. Instrumental methods are accurate, sensitive and rapid.
    - Students should be able to state advantages of instrumental methods compared with the chemical tests in this specification.
  - Lesson 04 - Required practical: Chromatography Lesson Plan Lesson Title
    - Required practical 6 - Chromatography (AT skills 1,4)
      - Suggested Activity:
        Investigate how paper chromatography can be used to separate and tell the
        difference between coloured substances.
        Equipment Required:
        For the basic method - per group
        • a 250 cm3 beaker
        • a wooden spill or pencil to support the chromatography paper
        • paper clip
        • a ruler
        • a pencil
        • distilled water
        • four known food colourings labelled A–D
        • unknown food colouring labelled U
        • rectangle of chromatography paper
        • five glass capillary melting point tubes.
  - Lesson 05 - How can we use chemical tests to identify unknown ionic compounds? Lesson Plan Lesson Title
    - Flame tests can be used to identify some metal ions (cations). Lithium, sodium, potassium, calcium and copper compounds produce distinctive colours in flame tests: ? lithium compounds result in a crimson flame
      ? sodium compounds result in a yellow flame
      ? potassium compounds result in a lilac flame
      ? calcium compounds result in an orange-red flame
      ? copper compounds result in a green flame.
      - Suggested Activity:
        Flame tests.
        Equipment Required:
        Splints. Metal oxide powders for testing flame tests.
    - If a sample containing a mixture of ions is used some flame colours can be masked
    - Carbonates react with dilute acids to form carbon dioxide gas. Carbon dioxide can be identified with limewater.
      - Suggested Activity:
        Students design a flow diagram on testing for positive ions.
    - Students should be able to identify species from the results of the tests in 4.8.3.1 to 4.8.3.5.
    - Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid. Silver chloride is white, silver bromide is cream and silver iodide is yellow.
      - Suggested Activity:
        Students design a flow diagram on testing for negative ions.
    - Flame colours of other metal ions are not required knowledge.
      - Suggested Activity:
        SEPARATE EW
        A group of students had four different colourless solutions in beakers 1, 2, 3 and 4,
        
        The students knew that the solutions were
        • sodium chloride
        • sodium iodide
        • sodium carbonate
        • potassium carbonate
        
        but did not know which solution was in each beaker.
        
        Plan a method that could be used to identify each solution.
        
        You may use the following reagents:
        • dilute nitric acid
        • silver nitrate solution.
        
        It is suggested that a flame test is used to identify the positive ions.
        
        Outline a method that could identify the four solutions.
        
        You should include the results of the tests you describe.
  - Lesson 06 - Required practical: Identifying ions Lesson Plan Lesson Title
    - Required practical 7 - identifying ions (AT skills 1,8)
      - Suggested Activity:
        Use of chemical tests to identify the ions in unknown single ionic compounds
        covering the ions from Flame tests and sulphates.
        Equipment Required:
        LiCl, NaCl, KCl, CaCl, CuCl powders
        Na2Co3, Na2So4, NaCl, NaBr, NaI 0.4M solutions
        Unknown Solution=0.4M KCl.
        0.4M barium choride sol,
        0.4M nitric acid, 0.05M silver nitrate sol.
        Limewater, boiling tubes & delivery tubes.
        Nichrome wires
    - Sulfate ions in solution produce a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid.
    - Sodium hydroxide solution can be used to identify some metal ions (cations).
    - Solutions of aluminium, calcium and magnesium ions form white precipitates when sodium hydroxide solution is added but only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution.
    - Solutions of copper(II), iron(II) and iron(III) ions form coloured precipitates when sodium hydroxide solution is added. Copper(II) forms a blue precipitate, iron(II) a green precipitate and iron(III) a brown precipitate.
    - Students should be able to write balanced equations for the reactions to produce the insoluble hydroxides.
    - Students are not expected to write equations for the production of sodium aluminate.
    - Flame emission spectroscopy is an example of an instrumental method used to analyse metal ions in solutions.
      - Suggested Activity:
        GCSE pod video on flame emission spectroscopy brilliantly explains the process. Link back to why it is a more reliable test than a basic flame test.
    - The sample is put into a flame and the light given out is passed through a spectroscope. The output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations.
    - Students should be able to interpret an instrumental result given appropriate data in chart or tabular form, when accompanied by a reference set in the same form, limited to flame emission spectroscopy.