SI Unit
Contents
Key Stage 4
Meaning
SI Units are the standard scientific units used by scientists around the world.
About SI Units
- SI stands for "Système international".
- SI units have been standardised around the world so that any experiment can be reproduced and so that components in machines are interchangeable.
- The USA does not always use SI Units. As a result of the confusion over units a space probe once crashed on Mars because one team of scientists was using inches and the other team was using hundredths of metre (centimetres) and a mistake was made converting from one to the other.
The SI Units you should know are in the following table:
| Measurement | SI Unit |
| Distance, Displacement, Wavelength | metres |
| Time | seconds |
| Temperature | degrees Celsius or Kelvin |
| Mass | kilograms |
| Area | metres squared |
| Volume | metres cubed |
| Force, Weight | Newtons |
| Speed and Velocity | metres per second |
| Density | kilograms per metre cubed |
| Angle | degrees |
| Acceleration | metres per second per second |
| Moment | Newton Metres |
| Energy, Work Done | Joules |
| Electrical Charge | Coulombs |
| Electrical Current | Amps |
| Potential Difference | Volts |
| Resistance | Ohms |
| Radioactivity | Becquerels |
| Radiation Dose | Ohms |
| Frequency | Hertz |
| Magnetic Flux Density | Teslas |
| Moles | Mol |
| Concentration | Mol per decimeter cubed |
| Light intensity | Lux |
References
AQA
- SI system of units, pages 266-267, GCSE Physics; Third Edition, Oxford University Press, AQA
- SI units, page 175, GCSE Combined Science Trilogy 1, Hodder, AQA
- SI units, page 19, GCSE Biology, CGP, AQA
- SI units, page 19, GCSE Combined Science Trilogy; Biology, CGP, AQA
- SI units, page 62, GCSE Chemistry, Hodder, AQA
- SI units, page 64, GCSE Physics, Hodder, AQA
- SI units, page 8, GCSE Biology; The Revision Guide, CGP, AQA
- SI units; interconversion of, pages 193-4, GCSE Combined Science Trilogy 1, Hodder, AQA
- Si units; interconversions of, pages 95-6, GCSE Chemistry, Hodder, AQA
Edexcel
- SI units, page 18, GCSE Chemistry, CGP, Edexcel
- SI units, page 19, GCSE Biology, CGP, Edexcel
- SI units, page 3, GCSE Biology, Pearson, Edexcel
OCR
- International system of units (SI units), pages 5, 301, Gateway GCSE Chemistry, Oxford, OCR
- Si units, pages 49, 285-286, Gateway GCSE Physics, Oxford, OCR
- SI units, pages 5, 301, Gateway GCSE Chemistry, Oxford, OCR