Lesson 11 — Activity 2: Mass

Getting Ready

Now that you have looked at metric lengths, you will turn your attention to mass.

Mass is the the physical volume or bulk of a solid body. In every day life, the word "weight" is often used when referring to mass. Keep in mind, however, that mass is the amount of matter in an object. Weight is a measure of how heavy an object is.

                  This scale is weighing fruit in kilograms.

Try This:

Thinking about the metric system and the imperial system once again, which weighs more:

  • A pound or a kilogram?
  • An ounce or a gram ?

A kilogram weighs more than a pound. There are 2.2 pounds in 1 kilogram.

An ounce weighs more than a gram. There are approximately 28.35 grams in an ounce.

Measuring mass in the metric system is very similar to measuring length in the metric system. All of the prefixes are the same and you move between the units the same way.

The main difference is that you only use three of the units when you talk about mass.

        Kilogram is one of the units we use.

Look at this chart:

milligram (mg)
centigram (cg)
decigram (dg)
gram (g)
dekagram (dag)
hectogram (hg)
kilogram (kg)

Have you decided what are the three measurements that you use from the chart? Did you choose kilogram, gram, and milligram? If you did, you are correct!

We can use the metric conversion chart once again as we are converting units of mass. This time, the basic unit measurement for measuring mass is a gram.

Metric Conversion Chart

(kilo — kg; hecto — hg; deka —  dag; gram — g; deci — dg; centi — cg;  milli — mg)

It is still 3 steps up to gram from milligram, so there are 1,000 milligrams in a gram. It is still 3 steps up to kilogram from gram, so there are 1,000 grams in a kilogram.

For example, what if you weighed a bag of jellybeans and it weighed 1,287 g? How many kilograms does it weigh?

It is 3 steps up from grams to kilograms. Since you are going up the stairs, you will move the decimal place 3 places to the left in your number. Since your number doesn't have a decimal showing, put it at the end of the number and then move it.

1,287. becomes 1.287

This tells you the bag of jellybeans weighs 1.287 kg.


What if you wanted to know how many milligrams the bag of jellybeans weighed?

It is 3 steps down from grams to milligrams. Since you are going down the stairs, you will move the decimal place 3 places to the right in your number. Notice that you don't have enough numbers to move the decimal 3 places to the right. Remember, that when this happens, add zeros into the blank spots.

1,287.000 becomes 1,287,000

The bag of jellybeans has a mass of 1,287,000 milligrams.

Try This:

What if you had a mass of 650,875.2 mg and wanted to know how many kg it was?

It is 6 steps up to kg from mg. Since you are going up the stairs, you will move the decimal place 6 places to the left in your number.

650,875.2 becomes 0.6508752

It would weigh 0.6508752 kg.

Go to the next page to try a Self-check Activity on converting metric weights.

Images courtesy of www.imagesgoogle.com