When every question in a set is labelled “forces”, “moles” or “microscopes”, you practise using a method, not choosing one. Exams mix the sciences, so choosing is part of the skill. This lesson belongs to double-award practice design.
How do I choose a method from an unlabelled question?
Use the same short routine every time.
- Underline the quantity asked for and write its unit.
- List what is given, with units.
- Find the link: a relationship, a definition or a ratio that joins what is given to what is asked.
- Check the units match the link before calculating.
- Check the size of the answer for sense.
Worked example (invented data)
Three unlabelled questions in one set. All data are invented.
Question A. A force of 4.0 N acts on a trolley of mass 2.0 kg on a smooth surface. Find its acceleration.
Asked: acceleration (m/s²). Given: force 4.0 N, mass 2.0 kg. Link: force = mass × acceleration.
a = F ÷ m = 4.0 ÷ 2.0 = 2.0 m/s². Check: 2.0 × 2.0 = 4.0 N.
Question B. A sample contains 12 g of magnesium. The relative atomic mass of magnesium is 24. How many moles is this?
Asked: amount in moles. Given: mass 12 g, relative atomic mass 24. Link: moles = mass ÷ relative atomic mass.
Moles = 12 ÷ 24 = 0.50 mol. Check: 0.50 × 24 = 12 g.
Question C. A plant cell appears 45 mm long in a drawing. Its real length is 0.15 mm. Find the magnification.
Asked: magnification. Given: image 45 mm, actual 0.15 mm. Link: magnification = image size ÷ actual size.
45 ÷ 0.15 = 300, so the magnification is ×300. Check: 0.15 × 300 = 45.
Three sciences, one routine, and no chapter title was needed.
The mistake to watch for
A student picks the formula by the look of the numbers.
Mistaken working on Question B: 12 ÷ 2.0 = 6, because “mass over something” worked in Question A.
The student reused a division from the previous question instead of checking what quantity was asked and what links it.
The correction is to write the asked quantity and its link first. Moles need a relative atomic mass, which the student did not use at all.
Check yourself
All data are invented, and these are unlabelled on purpose.
1. How many moles are in 4.0 g of sodium hydroxide? The relative formula mass of sodium hydroxide is 40.
Show answer
Moles = mass ÷ relative formula mass = 4.0 ÷ 40 = 0.10 mol. Check: 0.10 × 40 = 4.0 g.
2. A runner covers 100 m in 12.5 s. What is the average speed?
Show answer
Speed = distance ÷ time = 100 ÷ 12.5 = 8.0 m/s. Check: 8.0 × 12.5 = 100 m.
3. A cell image is 30 mm long at a magnification of ×200. What is the actual length?
Show answer
Actual size = image size ÷ magnification = 30 ÷ 200 = 0.15 mm. Check: 0.15 × 200 = 30 mm.
Where this leads next
Carry the routine into a new context with retesting a shared skill in a new science context. The mistake log and retest queue lets you record which chapters you needed a hint for, and the module practice set is unlabelled on purpose.
If you want a teacher to hand you unlabelled questions and discuss how you decide, that is part of online one-to-one Co-ordinated Sciences tuition.