5.4.134 - Atomic mass unit

Use the atomic mass unit (u) to express small masses and convert between this and SI units.

Use - atomic mass unit to connect the rule to the data and decision in the question.

This matters because - atomic mass unit determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - atomic mass unit to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Atomic mass unit is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.