# 4.22: Appropriate Metric Units of Mass or Capacity

**Practice**Appropriate Metric Units of Mass or Capacity

Have you ever used metric measurements to cook?

As some of the students enjoyed the metric playground, Billy discovered an exhibit near it on cooking and metrics. There were all kinds of pretend ingredients so you could try to figure out which metric unit would be best.

Billy looked at a recipe for cookies which called for 113.4 grams of butter. He began taking out four blocks of butter. Just as he did this, Tara noticed Billy and came over.

"What are you doing?" she asked.

"Measuring out 113.4 grams of butter," Billy said.

"Not that way," Tara laughed. "My mom went to school in England where everything is in metrics. You only need 1 stick of butter for your recipe."

"Are you sure?" Billy asked skeptically.

Are you? Do you understand how to measure in grams?

**This Concept is all about choosing the best metric unit. Pay attention and we will come back to this problem at the end of the Concept.**

### Guidance

**When you think about the metric units for measuring mass, how do you know when to measure things in grams, milligrams or kilograms?**

To really understand when to use each unit of measurement we have to understand a little more about the size of each unit. If you know measurements in the customary or standard system of measurement, such as ounces and pounds, you can compare them to measurements in the metric system of measurement, such as milligrams, grams, and kilograms.

**Grams compare with ounces, which measure really small things like a raisin.**

**Kilograms compare with pounds, which we use pounds to measure lots of things, like a textbook.**

**What about milligrams?**

Milligrams are very, very tiny. Think about how small a raisin is and recognize we would use grams to measure that. Scientists are one group of people who would measure the mass of very tiny items. These things would be measured in milligrams. If you think about things that would be seen under a microscope, you would measure the mass of those items in milligrams.

A milligram is of a gram.

**What about capacity? How do we choose the correct unit to measure capacity?**

There are two metric units for measuring capacity, milliliters and liters. This comparison may seem a little more obvious that the units for mass. A milliliter would be used to measure very small amounts of liquid. Milliliters are much smaller even than ounces. A liter would be used to measure much larger volumes of liquid.

A milliliter is of a liter.

**Would you measure a bottle of soda in liters or milliliters?**

You would measure it in liters. A 2 liter bottle of soda is a standard size for soda bottles. Think about milliliters as the amount of liquid in an eyedropper.

**Use what you have learned to select the correct metric unit for each item.**

#### Example A

The weight of five pennies

**Solution: Grams**

#### Example B

The amount of water in a bathtub.

**Solution: Liters**

#### Example C

The weight of a car

**Solution: Kilograms**

Now back to Billy and Tara and cooking with metrics.

As some of the students enjoyed the metric playground, Billy discovered an exhibit near it on cooking and metrics. There were all kinds of pretend ingredients so you could try to figure out which metric unit would be best.

Billy looked at a recipe for cookies which called for 113.4 grams of butter. He began taking out four blocks of butter. Just as he did this, Tara noticed Billy and came over.

"What are you doing?" she asked.

"Measuring out 113.4 grams of butter," Billy said.

"Not that way," Tara laughed. "My mom went to school in England where everything is in metrics. You only need 1 stick of butter for your recipe."

"Are you sure?" Billy asked skeptically.

Billy isn't sure that Tara is measuring accurately, but actually, she is.

There are about 453 grams in one pound.

A block of butter is around a pound.

Billy needs 113.4 grams of butter. That is about one - fourth of a block of butter.

**Tara is correct. Billy only needs one stick of butter.**

### Vocabulary

Here are the vocabulary words in this Concept.

- Customary System
- The system of measurement common in the United States, uses feet, inches, pounds, cups, gallons, etc.

- Capacity
- the amount of liquid an object or item can hold

- Mass
- the weight of an object

### Guided Practice

Here is one for you to try on your own.

Which unit of mass would you use to measure a handful of peanuts?

**Answer**

Since peanuts are very tiny, you should measure peanuts in grams.

### Video Review

Here are videos for review.

Khan Academy Conversion Between Metric Units

James Sousa Metric Unit Conversions

### Practice

Directions: Choose the best unit of either mass or capacity to measure each item.

1. A dictionary

2. A flea under a microscope

3. A jug of apple cider

4. An almond

5. Drops of water from an eyedropper

6. Ten dimes

7. A bucket of water

8. A baby bottle

9. A handful of rice

10. A large jug of water

11. A water tower

12. The water in a swimming pool

13. The weight of a boat

14. A handful of sand

15. The weight of a backpack

### Image Attributions

## Description

## Learning Objectives

Here you'll learn to choose appropriate metric units of mass or capacity given different measurement situations.