1.6 – Dimensional Analysis

Summer AP Chemistry HomeworkChapter 1

Dimensional Analysis Dimensional Analysis – The tool in chemistry

that allows us to convert between units by using their dimensions.

We use conversion factors in order to convert between what we want and what we have.

Setting Up Conversion Factors

We use conversion factors to convert between two different units.

We know that certain quantities are equal to one another. For example:

1 in = 2.54 cm Therefore, if I have 6 inches and I want to know

how many centimeters I have, then I use the conversion factor stated above to find:

We’ve Seen This Before!

Stoichiometry is all based on the use of conversion factors!

When you convert grams to moles, moles to moles, or any other stoichiometric conversion, you are just using dimensional analysis!

One Step Conversions

For one step conversions, all you need to think about is what you want and what you have.

From this you will simply need to look up the conversion factor that you need to use to convert between these.

Example You know that there are 5280 ft in one

mile. If you walk 10,000 ft, then how many miles have you walked?

Two or More Step Conversions

Often times, you need to do multiple conversions in order to complete the desired conversion.

For these problems, you need to first plot out the units you will need to convert between to get to your final answer. For example, if you need to convert 5 hours into seconds:

Hours Minutes Seconds1 hour = 60 minutes

1 minute = 60 seconds

Multi-Step Conversions

Conversions and the Metric System

Recall, that the metric system is based on the power of 10.

These powers of 10 will convert you back to the base unit. Once you are at the base unit, you can convert to the desired unit.

Metric Conversion Example

You have 425 cg, how many kg do you have?

Volume Conversions Volume often has units of some measurement

cubed (e.g. cm3, m3, etc.) This means that you need to cube the units

when you are doing this conversion. For example, convert 2.00 in3 to cm3 (2.54 cm =

1 in)

Extra PracticeSee the problems in section 1.6 and in the end of chapter problems for more practice on this

section.