GCSE Chemistry Required Practicals - Edexcel Pearson

General Tips

• Variables:
  • Independent Variable: The factor you change.
  • Dependent Variable: The factor you measure which changes as a result.
  • Control Variables: The factors you keep constant to ensure accuracy.
• Equipment: Always specify the equipment used (e.g., measure length with a ruler).
• Safety: Always state obvious safety measures (e.g., use goggles and gloves when handling chemicals).
• Accuracy:
  • Reduce errors (e.g., align eye level to measurement to avoid parallax error).
  • Take multiple or repeat measurements to calculate a mean.
• Writing Answers:
  • Bullet point format is recommended for clarity.
  • Use proper English (e.g., "heat the water gently on a tripod over a Bunsen burner flame").
• Resources: Watch practicals on Mansbury Education for visual guidance.

Practical 1: Chromatography

• Purpose: Separate different solutes or particles in a mixture.
• Procedure:
  • Place a spot of solution above the bottom of chromatography paper (stationary phase).
  • Draw a pencil line at the same point.
  • Suspend the paper in a beaker with distilled water (mobile phase).
  • Allow water to diffuse up the paper, separating particles.
  • Calculate RF value: (distance solute moves) / (distance mobile phase moves).
  • Compare RF values with known values to identify substances.

Practical 2: Investigating pH

• Purpose: Determine the pH of a reaction between different masses of a base and a fixed volume of acid.
• Procedure:
  • Mix powdered base with dilute acid.
  • Use universal indicator paper to measure pH.
  • Continue until neutralization (pH 7).
  • Calculate concentration using moles if needed.

Practical 3: Preparing Copper Sulfate Crystals

• Purpose: Produce copper sulfate crystals from copper oxide and sulfuric acid.
• Procedure:
  • Heat sulfuric acid in a beaker.
  • Add excess copper oxide (unreacted powder at the bottom).
  • Filter out unreacted copper oxide.
  • Heat solution in an evaporating basin over water on a Bunsen burner.
  • Obtain solid copper sulfate crystals.

Practical 4: Electrolysis

• Purpose: Electrolyze copper sulfate solution using different electrodes.
• Inert Graphite Electrodes:
  • Cathode: Copper produced.
  • Anode: Oxygen produced.
  • Leftover: Hydrogen and sulfate ions, forming sulfuric acid.
• Copper Electrodes:
  • Anode: Copper atoms lose electrons, form Cu²⁺ ions.
  • Cathode: Cu²⁺ ions gain electrons, form copper atoms.
  • Result: Mass decrease in anode, increase in cathode; used to purify copper.

Practical 5: Titration

• Purpose: Determine unknown concentration of acid/alkali using known concentration of the other.
• Procedure:
  • Measure a specific volume of alkali and place in a conical flask with an indicator (e.g., methyl orange).
  • Fill burette with acid, perform rough titration first.
  • Perform precise titration, adding acid dropwise near endpoint.
  • Calculate concentration using the volume at neutralization and moles.

Practical 6: Rates of Reaction

• Purpose: Observe rate of reaction using two methods.
• Method 1 (Gas Production):
  • Use a conical flask with a tube leading to an inverted measuring cylinder.
  • Measure the volume of gas produced at regular intervals.
  • Plot reaction curve and compare rates.
• Method 2 (Turbidity/Cloudiness):
  • React sodium thiosulfate and hydrochloric acid in a conical flask over a paper with a cross.
  • Time how long the cross takes to disappear.
  • Change variables (e.g., temperature, concentration) and compare times.

Practical 7: Identifying Ions

• Metal Ions (Flame Test):
  • Dipping nichrome wire in solution/powder, place in Bunsen flame.
• Non-Metal Ions:
  • Carbonate Ions: Add hydrochloric acid (bubbles formed), test gas with lime water (turns cloudy).
  • Halide Ions: Add silver nitrate and nitric acid.
    • Chloride: White precipitate.
    • Bromide: Cream precipitate.
    • Iodide: Yellow precipitate.
  • Sulfate Ions: Add hydrochloric acid and barium chloride (white precipitate).

Practical 8: Combustion of Alcohols

• Purpose: Compare energy released by different alcohols.
• Procedure:
  • Place alcohol in spirit burner under a copper calorimeter with water.
  • Measure start and end temperature of water.
  • Calculate temperature difference to compare different alcohols.

For more information, watch related videos and tutorials on Mansbury Education.