Algebraic Approach

An algebraic approach can be used for density calculations also. If you are familiar with algebra you know that it involves representing a relationship with an equation and using symbols to represent quantities. (The following examples are also shown in your workbook in Example 21.)

You know that density equals mass divided by volume. That relationship can then be expressed in many ways by carefully rearranging the equation. Mass equals volume times density. Volume equals mass divided by density. Which form of the equation is used depends on what you are trying to figure out.	D=	m v
	D x v = m or m = D x v
	v =	m D
This example asks the same question as before, but the approach to the answer is different. First write down the appropriate form of the equation--or write down the standard form and then rearrange it. Next substitute the known values into the equation and carry out the calculations.	Given that the density is 2.5 g/mL, how much would 6.0 mL weigh?
	m = D x v m = 2.5 g/mL x 6.0 mL m = 15 g
In this example we are asked for the volume. The volume equals the mass over the density. So the volume is going to be equal to 4.0 g divided by 2.5 g/mL. Then carry out the calculations to get the volume.	Given that the density is 2.5 g/mL, how much volume would 4.0 g take up?
	v =	m D
	v =	4.0 g 2.5 g/mL
	v =	1.6 mL

Next, answer the questions in the following quick quiz using whichever method you prefer.

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E-mail instructor: Eden Francis