O Level Biology Practical 2020 Answers 2021 ❲100% PREMIUM❳

Use clear, continuous lines without shading and include a magnification calculation .

This question focused on the breakdown of hydrogen peroxide ( H2O2cap H sub 2 cap O sub 2

Always record time to the nearest second and use a measuring cylinder for precise volumes.

Candidates had to identify data points deviating significantly from the established trend line and suggest human error or equipment limitations as the root cause. Crucial Sources of Error and Improvements o level biology practical 2020 answers

: Points should be marked with a small 'x'. The line of best fit should be a smooth curve or a series of straight lines joining the points, depending on the trend.

: Students performed the Benedict’s test. Successful responses required a structured table with correct headings (e.g., sample name, time taken for color change, and final glucose concentration).

Use a thermostatically controlled electronic water bath instead of a beaker heated by a Bunsen burner. 2. Subjective Color Determination Use clear, continuous lines without shading and include

Identifying reducing sugars, proteins, starch, and fats using standard chemical reagents.

Use at least half the provided grid and a ruled best-fit line .

| Topic Area | Common Practicals | Key Variables & Observations | | :--- | :--- | :--- | | | Testing for starch, reducing sugars, proteins, and fats. | Observations: Color changes (e.g., blue-black for starch, brick-red precipitate for reducing sugars, violet for proteins, translucent spot for fats). | | Enzymes | Investigating the effect of temperature or pH on enzyme activity (e.g., catalase, amylase). | Independent Variable: Temperature or pH. Dependent Variable: Rate of reaction (e.g., time for a color change, volume of gas produced). Control: Boiled enzyme or without substrate. | | Osmosis & Diffusion | Investigating the effect of solute concentration on the mass or length of plant tissue (e.g., potato cylinders). | Independent Variable: Concentration of the solution. Dependent Variable: Change in mass or length of the tissue. Control: Distilled water (isotonic condition). | | Plant Biology | Examining leaf structure (stomata), root hair cells, or cross-sections of stems. | Observations: Identifying and labeling xylem, phloem, palisade mesophyll cells, guard cells, and stomata. | | Microscopy | Preparing and observing stained slides of onion cells or cheek cells. | Observations: Magnification calculation, drawing cells, labeling organelles (nucleus, cell wall, cytoplasm). | Crucial Sources of Error and Improvements : Points

Below is a summary of the core practical findings and answers based on the official Mark Schemes Examiner Reports for that year. Paper 31 & 32 (Practical Test) 1. Pigment Release Experiment (Beetroot)

Label lines must be drawn with a ruler, touch the target structure precisely, and never cross each other. No arrowheads should be used. Magnification Calculation Formula