Lesson 12 — Activity 2: Mass
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Lesson 12 — Activity 2:
Mass
In the previous lesson, you learned all about metric lengths. Now you will take a look at mass and weight.
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Technically speaking, the metric system measures not weight but mass.
Weight is the measurement of how strongly gravity pulls an object toward Earth. Mass, however, is the measurement of the amount of matter an object has.
If you travelled to the moon, your weight would change, so you would feel lighter. But your mass would remain the same, so all of you would still be there.
What you need to remember is that mass is the amount of matter in an object. Weight is a measure of how heavy an object is.
The three units of measurement that we use the most when talking about mass are the milligram, the gram, and the kilogram. So what is the difference?
A very small unit used to measure mass is the milligram (mg). Regularly, doctors will write prescriptions to their patients. Most medications have guidelines for dosage amounts in milligrams (mg). Doctors need to figure out how many milligrams of medication each patient will need, depending on their weight.
Things that can be measured in milligrams include:
- a raindrop
- a grain of rice
- a toothpick
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Grams
A paperclip weighs about 1 gram.
Hold one small paperclip in your hand. Does that weigh a lot? No! A gram is very light. That is why you often see things measured in hundreds of grams.
Grams are often written as g (for short), so "300 g" means "300 grams".
Things that can be measured in grams include:
- flour needed in a recipe
- a sheet of paper
- a piece of gum
Things that can be measured in kilograms include:
- the mass of a bottle of water
- a bag of apples
- a package of ground beef
- the mass of a bottle of water
- a bag of apples
- a package of ground beef
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.
For example:
1 kilogram (kg) = 1000 grams (g)
1 gram (g) = 1000 milligrams (mg)
Remember from the last lesson on how to move the decimal point on the chart? Here are the steps again:
1. Determine your starting point.
2. Count the jumps to your ending point.
3. Move the decimal the same number of jumps in the same direction.
You try it! Use the conversion chart above to find the amounts.
How many grams (g) are in 35 kilograms (kg)?
35,000 grams (g)
How many grams (g) are in 35 kilograms (kg)?
35,000 grams (g)
How many grams (g) are in 5,900 milligrams (mg)?
5.9 grams (g)
When working with mass at school, at work, at home, or in your community, it is important that you choose the appropriate unit of measure. For example, when getting a prescription from the doctor, it is easier for the pharmacist to measure 350 milligrams than to measure 0.00035 kilograms!
Let's
practise choosing the appropriate mass for various items. For example,
Mary used the device shown to measure the mass of the apple. Which unit
of measurement is the device displaying?
- milligrams (mg)
- grams (g)
- kilograms (kg)
The most appropriate unit would be grams!
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Ben used a bathroom scale to measure his weight. Which is the best unit of measurement for showing Ben's weight?
- milligrams (mg)
- grams (g)
- kilograms (kg)
Ben used a bathroom scale to measure his weight. Which is the best unit of measurement for showing Ben's weight?
- milligrams (mg)
- grams (g)
- kilograms (kg)
The most appropriate unit would be kilograms (kg)!
A pharmacist wants to measure out some pills for a patient. Which is the best unit of measurement?
- milligrams (mg)
- grams (g)
- kilograms (kg)
The most appropriate unit would be milligrams (mg)!
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