Scientific Quantities and Units
Use scientific quantities with correct units: pair every measurement with its unit (metres, kilograms, seconds, newtons, joules), pick sensible prefixes like milli- and kilo-, convert between them, and call chemicals by their proper scientific names
What a learner can do afterwards
- Record measurements with the correct unit and symbol (e.g., 2.5 kg, 30 s, 1.2 m)
- Convert between prefixed units when comparing or calculating (e.g., 2500 mL = 2.5 L, 0.4 km = 400 m)
- Use proper chemical names for common substances in written work (e.g., sodium chloride rather than just 'salt')
The lesson
In science, a number by itself doesn't say much. Every measurement needs a unit attached, like 2.5 kilograms, not just 2.5. The unit tells you what kind of quantity you're looking at, and how big it really is.
Scientists use a small set of standard units. Length is measured in metres (m), mass in kilograms (kg), and time in seconds (s). Force is measured in newtons (N), and energy in joules (J). Each one has its own symbol.
A lab tech measures 750 mL of liquid, but the recipe asks for litres. Since 1000 mL make 1 L, 750 mL is 0.75 L. Getting the prefix right means comparing numbers on the same scale.
When you write about chemicals, use their real scientific name. 'Salt' should be sodium chloride, and 'baking soda' is sodium bicarbonate. It's more precise, and it's the name a scientist expects.
Every quantity needs a unit and symbol, the right prefix keeps the size honest, and chemicals deserve their real names.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.