Chemistry / Unit 1 Chem 0121 short lesson, about 20 seconds
Exact Numbers vs. Measured Numbers
Captions available
The idea
An exact number, from counting or a definition, carries no uncertainty; a measured number always carries uncertainty.
In practice
Counting twelve eggs in a carton gives an exact number; weighing those eggs on a scale gives a measured, uncertain number.
Where people slip
A defined conversion, like twelve inches to a foot, never limits how many significant figures a calculation keeps.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Unlocks
Something wrong in this lesson? Flag it · Sources for Chemistry