IGCSE Biology Paper 6: Practical Notes by Cattaystudies

Contents

• Drawing Diagrams
• Calculating Magnification
• Safety Issues
• Chemical Tests
• Making Comparisons
• Identifying Errors and Improvements
• Drawing Tables and Graphs
• Miscellaneous Questions
• Control Variables
• Experiment Planning
• Possible Exam Topics

Drawing Diagrams

• Use a sharp pencil, clear outlines, no shading
• Make diagrams large; no sketching, use one thin line
• Label with lines pointing directly (no arrowheads), use a ruler
• Memorize labels for common hard diagrams

Calculating Magnification

• Formula: Magnification = Image Size / Actual Size
  • Conversion: 1m = 100cm, 1cm = 10mm, 1mm = 1000μm
  • Rearrange for Image Size or Actual Size
  • Units for magnification is X (e.g., X100)

Safety Issues and Mitigation

• Hot Test Tubes: Use tongs, heat-resistant gloves
• Cutting: Use a flat surface, cut away from fingers
• Exercise: Avoid in extreme conditions, wear proper footwear
• Food Allergies: Exclude allergic participants
• Chemical Handling: Wear gloves, goggles, avoid flames near ethanol

Chemical Tests

• Starch: Iodine solution (blue-black if positive)
• Protein: Biuret solution (lilac if positive)
• Glucose: Benedict's solution, heat (brick red if positive)
• Vitamin C: DCPIP solution (clear if positive)
• Fats: Ethanol and water (cloudy emulsion if positive)
• CO2: Limewater test, Hydrogencarbonate indicator

Making Comparisons

• Focus on visible points; avoid size unless scale provided
• Use diagram labels as guidance

Identifying Errors and Improvements

• Common errors: lack of repeats, gas loss, inconsistent shaking, subjective color changes, and contamination
• Improvements: repeat tests, use machines, measure accurately, use syringes instead of pipettes

Drawing Tables

• Headers must include units
• Align data to decimal precision
• Include averages where necessary

Drawing Graphs

• Label axes with units, use appropriate scales
• Use crosses for data points
• Line of best fit for scatter graphs; join points for line graphs
• Describe trends using increase/decrease terms

Miscellaneous Questions

• Importance of repetition: identify anomalies, calculate averages
• Surface area estimation with grids
• Importance of random sampling
• Use of control experiments to identify IV impact

Control Variables

• Maintain uniform conditions: temperature, species, concentration, pH, duration
• Use equipment like thermostats, buffers, and measuring cylinders

Planning Experiments (6-mark questions)

• IDCSRA mnemonic: Independent, Dependent, Control, Safety, Repeat, Average
• State and control variables with methods
• Always repeat and calculate averages

Possible Exam Topics

1. Photosynthesis rate factors: temperature, light, CO2
2. Water uptake factors: temperature, humidity
3. Germination factors: temperature, oxygen
4. Enzyme activity factors: temperature, pH
5. Exercise effects on heart/breathing rate

Important Information on Graphs and Tables

• Use solidus (/) for units
• Plot IV on x-axis, DV on y-axis
• Choose scales covering half the grid
• Mark data points accurately with crosses or dots
• Use single, smooth lines for best-fit
• Record data reflecting precision of instruments
• Bar and pie charts for non-numeric variables