Capacity
Capacity is the amount a container can hold.
To compare the capacity of two containers, you can put or pour what is in one container into
another.
Capacity comparison
Consider the following experiment over a sink, water table, or large bucket.
This experiment needs a sink or shallow bucket and two different sized cups,
such as a
coffee mug and a small cup.
In the experiment, the cup is filled with water while the coffee mug sits in
the sink/bucket.
After the cup has been filled with water, the water is poured from this cup
into the coffee mug that is sitting in the sink.
What do you think will happen to the coffee mug?
Will the two cups hold the same amount of water?
Record your thoughts using a method of your choice.
- If the water overflowed when it was poured into the second cup, what did that tell you about
the capacity of the first container?
- If the second cup had more space for more water, what did that tell you about its capacity?
You decide
Two students took identical cups of water, and each poured one full cup into
two separate containers.
Student A poured their cup of water into Container 1.
The following image displays Container 1 after the water was poured into it.
Student B poured their cup of water into Container 2.
The following image displays Container 2 after the water was poured into it.
Student A said that the volume of water is the same in both containers.
Student B said Container 2 has more water.
Who do you agree with? Explain your thinking using a method of your choice.
When you are ready, press ‘Answer’ to reveal which student was correct.
Answer
Which student was correct?
Student A is correct because both cups had identical amounts of water in them to start
with. The amount won’t change just because the containers are different sizes.
It just looks like there’s more water in Container 2 because it’s almost full.
If you poured the water back into the cups, both cups would still have the same amount of
water.
As well, if you were to pour Container 1 into an empty Container 2, it would look just
the same as it does now, proving they have the same amount of water.
Measuring capacity
Litres and millilitres are standard units that we use to measure capacity.
You can also use any objects that you have a lot of, and that are identical to measure capacity.
When measuring capacity, it is best to choose something that is small to be precise, but still
large enough to count. Here are some examples:
- spoonfuls of water
- spoonfuls of sand
- spoonfuls of rice
- individual marbles
- individual beads
- individual unifix cubes
Can you think of other non-standard units that would be good to measure capacity?
Press ‘Cup-acity’ to complete a measuring activity. This activity is optional.
Cup-acity
Cup-acity
Complete the following activity and record your results. You can record the results of
your experiment using a method of your choice.
-
Choose a cup to fill with water. Select different-sized cups as non-standard
measuring tools.
-
How many of the smaller cups, carefully filled, does it take to fill the
first cup?
-
Use another cup of a different size to measure.
-
How many small cup units might it take to fill the container completely this
time?
-
What do you need to consider when finding capacity?
-
Did you fill the cup to the same level each time?
Answer the following questions about the experiment:
- How can you make sure you filled your cup to the top?
- If you fill your first cup with different kinds of cups, what did you notice?
- How can you communicate the capacity of the first cup using different sized cups?
Underfilling and overfilling
It’s important to be accurate when making measurements. Two common ways to get an inaccurate
capacity measurement are to underfill or overfill the container you are measuring.
Underfilling
Underfilling means that a container is not filled completely.
For example, consider the following jar that has been filled to the top with 30 marbles.
The space between the marbles tells us that the jar is underfilled.
What could we use instead of marbles that would create fewer or no gaps?
Overfilling means that a container can’t hold everything: it
overflows.
For example, consider the following cup of rice. The cup has been filled past its rim
using spoonfuls of rice.
The rice above the rim of the cup lets us know that it has been overfilled.
Your turn
The following image displays seven bottles that are different sizes.
How could you use the liquid in each bottle to help figure out which bottle holds the most liquid
(has the greatest capacity)?
Now examine the following bucket.
If we wanted to measure the capacity of the bucket, explain how we could use the bottles to help
figure out how much liquid the bucket holds.
Hint: Remember to use the same unit when measuring. You could measure in cups or in
spoons.
When you are ready, press ‘Answers’ to reveal possible responses to the questions.
Answers
How could you use the liquid in each bottle to help figure out which bottle holds
the most liquid (has the greatest capacity)?
We could use the liquid in each bottle to help figure out which bottle holds the most
liquid by emptying all the bottles except one.
We would choose the bottle that we thought was either the greatest capacity or the least.
We would fill the bottle up and then empty it into the other bottles.
If the water overfilled the bottle, we would know that the original bottle had a greater
capacity.
If it underfilled, then we would know the original bottle had a lesser capacity.
We would do this until we got them all in order.
If we wanted to measure the capacity of the bucket, explain how we could use the
bottles to help figure out how much liquid the bucket holds.
If we wanted to measure the capacity of the bucket, we would choose a single bottle to
help figure out how much liquid the bucket holds. We could then count the number of
bottles it takes to fill the bucket.
Press
the ‘Activity’ button to access Container Comparison.
