Microscopy Required Practical GCSE: How to Secure Full Marks

The microscopy required practical GCSE appears in AQA, Edexcel and OCR Biology and is a regular source of lost marks. Students often remember how to use a microscope but struggle to describe the method precisely or calculate magnification correctly. Examiners reward clarity, correct terminology and accurate calculations — not vague descriptions.

How to Prepare a Slide Correctly (Method Marks)

For a standard light microscopy practical, you may be asked to prepare a slide of onion epidermis or cheek cells.

A full-mark method answer should include:

1. Place a thin layer of cells onto a clean glass slide.

2. Add a drop of stain (iodine for plant cells, methylene blue for animal cells).

3. Carefully lower a coverslip at an angle using a mounted needle to avoid air bubbles.

4. Remove excess stain with tissue.

5. Start with the lowest magnification before increasing.

Examiners expect the reason for staining: to make cell structures more visible. Simply saying “add stain” without explaining why can limit marks.

For structured revision across required practicals, see KayScience.com.

Calculating Magnification (Where Students Lose Marks)

The required formula is:

Magnification = image size ÷ actual size

You must convert units into the same form before calculating.

Example Calculation

A cell measures 40 mm on a printed image.
The actual cell size is 20 µm.

First convert 40 mm into micrometres:

40 mm = 40,000 µm

Now calculate:

Magnification = 40,000 ÷ 20
Magnification = 2000×

Common error: forgetting unit conversion. This alone costs one mark immediately.

Practise similar calculation questions in Exam Questions.

What Examiners Commonly Penalise

Across AQA, Edexcel and OCR mark schemes, typical mistakes include:

• Writing “zoom” instead of “magnification”

• Forgetting to mention starting on low power

• Not explaining why a coverslip is lowered at an angle

• Incorrect unit conversion (mm to µm)

• Missing multiplication symbol (×) after the magnification value

Precision matters. Scientific vocabulary is assessed.

GCSE-Style Question

Question (4 marks)
Describe how a student would prepare a slide of cheek cells for observation under a light microscope.

Exam Technique Tip

When describing the microscopy required practical, write in clear sequential steps and include at least one reason for a step (e.g., stain improves visibility, angle prevents air bubbles). This pushes answers into higher mark bands.

For targeted support with exam-style practical questions, visit https://kayscience.com/tuition-timetable.