SI Units and Measurement
Chemistry uses SI units like kilogram, metre, litre and mole.
About this topic
Scientists use the International System of Units (SI) for consistent communication. Base units include the kilogram for mass, metre for length, second for time, kelvin for temperature, mole for amount of substance, ampere for current and candela for luminous intensity. Derived units, such as the litre or joule, come from the base units.
Prefixes scale units by powers of ten: kilo is 1000, centi is one hundredth, milli is one thousandth, micro is one millionth. Converting between them uses dimensional analysis: multiply by a conversion factor equal to one so that unwanted units cancel. For example, to convert 2500 mg to grams, multiply 2500 mg by 1 g / 1000 mg to get 2.5 g.
Accuracy and precision are different ideas. Accuracy is how close a measurement is to the true value; precision is how close repeated measurements are to each other. A scale that always reads 0.5 g too high is precise but not accurate. Measuring tools matter too: a graduated cylinder gives better volume than a beaker.
Real life shows why units matter: in 1999 a NASA Mars orbiter was lost because one team used pound-force and another newtons. Always write units with your numbers, and remember that Celsius plus 273.15 gives kelvin, which gas law calculations need.
Key ideas
- Prefixes: kilo, centi, milli
- Accuracy vs precision
- Always include units
Quick check
Use cases: where SI Units and Measurement helps
- Homework: review the key idea behind SI Units and Measurement before you start a problem set.
- Exam revision: use the quick check to test whether you can recall SI Units and Measurement without notes.
- Visual learning: play with the interactive lab to see how SI Units and Measurement changes when you adjust its inputs.
- Teaching a friend: explain SI Units and Measurement in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is SI Units and Measurement?
Chemistry uses SI units like kilogram, metre, litre and mole.
What will I learn in SI Units and Measurement?
Prefixes: kilo, centi, milli. Accuracy vs precision. Always include units.
Is SI Units and Measurement part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the SI Units and Measurement lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study SI Units and Measurement?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.