Experimental Design & Method Writing: Writing A Correct Experimental Method (Step-By-Step Logic) (Copy)

Experimental Design & Method Writing

Writing A Correct Experimental Method (Step-By-Step Logic)

Purpose of Writing an Experimental Method in ATP

• Experimental method questions assess whether a candidate:
  • Understands how an experiment is carried out logically
  • Knows the correct sequence of steps
  • Can link apparatus, variables, and safety into a coherent plan
• The method is judged on:
  • Clarity
  • Order
  • Relevance
• Marks are awarded step-by-step, not for overall description

Examiner’s Core Expectation from a Method Answer

• Examiner expects:
  • A logical sequence of actions
  • Each step clearly earning one mark
• Examiner does not expect:
  • Background theory
  • Chemical equations (unless explicitly asked)
  • Results or conclusions

General Structure of a Correct Method Answer

• A correct method should follow this fixed logical flow:
  1. Preparation of apparatus and materials
  2. Measurement of quantities
  3. Execution of the experiment
  4. Measurement/collection of results
  5. Repetition where relevant
• Skipping any logical stage often results in lost marks

Step 1: Identifying and Preparing Apparatus

• Always begin with:
  • Correct apparatus names
  • Suitable measuring equipment
• Examples:
  • Measuring cylinder for volume
  • Balance for mass
  • Thermometer for temperature
• Examiner rewards:
  • Appropriate choice of apparatus
• Examiner penalises:
  • Vague terms such as “equipment” or “tools”

Step 2: Measuring Quantities Accurately

• Method must include:
  • What is measured
  • How it is measured
• Examples:
  • Measure 25 cm³ of acid using a measuring cylinder
  • Weigh 2.0 g of magnesium using a balance
• Quantities:
  • Should be realistic
  • Should match the context of the experiment
• Missing measurement steps = lost marks

Step 3: Carrying Out the Reaction (Core Procedure)

• This is the main body of the method
• Must include:
  • Correct order of actions
  • Clear verbs (add, heat, mix, record)
• Examples:
  • Add the acid to the solid
  • Heat the solution gently
  • Stir the mixture continuously
• Examiner looks for:
  • Logical progression
  • No missing steps

Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Chemistry Full Scale Course

Step 4: Controlling Variables Within the Method

• Good methods implicitly or explicitly control variables
• Controlled variables may include:
  • Temperature
  • Volume of reactants
  • Concentration
  • Surface area
• Example phrasing:
  • Keep the volume of acid constant
  • Maintain the same temperature throughout
• Examiner rewards:
  • Awareness of fair testing
• Examiner penalises:
  • Ignoring variable control entirely

Step 5: Recording Results Correctly

• A complete method includes:
  • What is recorded
  • How often it is recorded
• Examples:
  • Record the volume of gas every 30 seconds
  • Measure the temperature at regular intervals
• Avoid vague statements:
  • “Note the result”
  • “See what happens”

Step 6: Repetition and Reliability

• High-scoring methods often include:
  • Repeating the experiment
  • Averaging results
• Example:
  • Repeat the experiment twice and calculate the mean
• Examiner awards marks for:
  • Awareness of reliability
• Examiner does not accept:
  • “Be more careful” as a substitute

Step 7: Safety Considerations (Only When Relevant)

• Safety points should be:
  • Relevant
  • Specific
• Common valid safety steps:
  • Wear safety goggles
  • Handle acids carefully
  • Heat using a water bath
• Irrelevant safety points:
  • Do not gain marks
• Overloading with safety:
  • Does not earn extra marks

Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Chemistry Full Scale Course

Language Rules for Writing a Method

• Use:
  • Imperative verbs (measure, add, record)
  • Short, direct sentences
• Avoid:
  • First person (“I”, “we”)
  • Casual language
  • Paragraphs
• Each step should be:
  • One clear action
  • One potential mark

Common Method Writing Mistakes

• Writing theory instead of procedure
• Missing measurements
• Wrong apparatus choice
• Incorrect sequence
• Including observations or conclusions
• Using vague phrases:
  • “Do the experiment”
  • “Repeat properly”

Example of Poor vs Correct Method Logic

Method Questions Linked to Different Experiment Types

• Rate of reaction:
  • Emphasis on timing and repetition
• Titration:
  • Emphasis on burette, endpoint, accuracy
• Temperature experiments:
  • Emphasis on thermometer use and insulation
• Gas collection:
  • Emphasis on correct collection method

Examiner Marking Logic for Method Questions

• Typically:
  • 1 mark per valid step
• Steps must be:
  • In correct order
  • Scientifically correct
• Extra steps:
  • Are ignored
  • Can cancel marks if incorrect

Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Chemistry Full Scale Course

Using the Mark Allocation to Shape the Method

• Always check:
  • Number of marks
• Example:
  • 4-mark method = 4 clear steps
• Writing 8 steps for 4 marks:
  • Wastes time
  • Increases error risk

ATP-Focused Method Writing Strategy

• Read the experiment aim carefully
• Identify:
  • What is changed
  • What is measured
• Build the method around:
  • That relationship
• Write steps that:
  • Directly lead to measurable results

Final Examiner-Focused Principles for Method Writing

• Logical sequence over detail
• Accuracy over length
• One step = one mark
• Method must be:
  • Clear
  • Structured
  • Realistic