Chemistry Conversion Question

Question

When doing metric/unit conversions, how do you know when it is supposed to be multiple steps? For example one of my homework questions asks how many centimeters are in 8 nanometers. I have to go from

nm --> m --> cm. Is there a method to remember when you need to convert to another unit first?

Answer 1

You don't HAVE to go from nm -> m -> cm, but you can if you wish to.

As long as you know the conversion factor, you can use any steps you want. In the present example, most of us know there are 10⁹ nm in 1 m and there are 100 cm in 1 m, so going from nm -> m -> cm makes sense. But if you knew that there were 10⁷ nanometers in 1 cm, you wouldn't need the m conversion. I hope that makes sense.

8 nm x 1 m / 10⁹ nm x 100 cm / m = 8x10^-7 cm

8 nm x 1 cm / 10⁷ nm = 8x10^-7 cm