Scientists use the International System of Units - SI units. The table shows some common units.
|Quantity||Unit name||Unit symbol|
Scientists measure a wide range of quantities, some very large and some very small. Measurements for different orders of magnitude have specific prefixes:
|Prefix name||Prefix symbol||Factor||Power|
|nano||n||0.000 000 001||×10-9|
To convert between a unit with difference prefixes, multiplication or division of the right factor of ten (10, 100, 1,000) is used.
Always do a sense check when multiplying or dividing and ask, “Is the answer expected to be larger or smaller?”
Convert 5 cm into mm.
1 cm = 10 mm so the conversion is ×10
5 × 10 = 50 mm
This is what would be expected because millimetres are smaller than centimetres.
Time is dealt with differently if it is recorded in minutes, as this is not an SI unit:
Convert 2 minutes 40 s into s
2 minutes = 2 × 60 = 120 s
2 minutes 40 s = 120 + 40
= 160 s