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Unit Conversion for the Sciences

Units of measurement in the sciences use the International System of Units, better known as SI units, which provide a standard for measuring the physical properties of matter. Typical SI units are seconds (s), metres (m), and kilograms (kg). Other SI units of measurement can be derived from the base units. Typical SI derived units are cubic metres (m3) and metres per second (m/s). When a measurement is excessively high or low in magnitude when expressed as its SI unit, prefixes are often used to denote an order of magnitude to make the number itself more manageable. The following table may be used to convert between common SI prefixes

Prefix

Scientific Notation

To convert to SI unit

To convert from SI unit

Mega (M)

106

x 1 000 000

÷ 1 000 000

Kilo (k)

103

x 100

÷ 1 000

-

100

-

-

Milli (m)

10-3

÷ 1 000

x 1 000

Micro (μ)

10-6

÷ 1 000 000

x 1 000 000

Nano (n)

10-9

÷ 1 000 000 000

x 1 000 000 000

Pico (p)

10-12

÷ 1 000 000 000 000

x 1 000 000 000 000

Example:

How many microlitres are in 2 millilitres? Note: Though litre (L) is not an SI unit of measurement, it is still commonly used in science. The SI unit for volume is m3.

Solution:

This question is asking us to convert millilitres (mL) into microlitres (µL). To complete this question, we must first convert 2 mL into SI unit litres (L), and then convert from L into µL. To do this, we refer to the prefix column of the table to find the milli prefix and cross over to the To convert to SI unit column to see that in order to convert 2 mL into litres, we divide by 1000:

2 mL/1000 = 0.002 L

We then refer to the prefix column of the table to find the micro prefix and cross over to the To convert from SI unit column to see that to convert from 0.002 L into µL, we multiply by 1 000 000.

0.002 L x 1 000 000 = 2000 μL 

Therefore, we find that 2 000 µL are contained in 2 mL. This volume can also be expressed in scientific notation as 2 x 10μL.

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