Question

Show how one would set up a ration to determine the mass of a substance given that the density was 5.6g/ml with a volume of 3.7ml. What is the mass?

Answer 1

`rho("density")="mass"/"volume"`

Explanation:

And thus mass is simply the product:

`"mass"` `=` `"volume "xx" density"`.

For your problem, `"mass"` `=` `5.6*g*cancel(mL^-1)xx3.7*cancel(mL)` `=` `??g`

Note that using the units in the calculation automatically gives the correct units, `"grams"`, for the answer. This is called dimensional analysis, and you can use it as a check on your calculations. It is also too easy to divide when you should have mulitplied, or multiplied when you should divide. Solving a problem dimensionally helps to avoid this.