Minds On
Balancing act
Examine the following balance scale:
On one side of the balance scale there is one object. On the other side of the balance scale there are two objects.
Think about the following questions:
- What do you notice about the scale and the objects?
- What do you wonder about the objects?
If you were told that one small object has the same mass as one large object, would it change how much mass you thought might be on each side of the balance?
How do you think you could balance the two sides of the balance scale?
Action
Mass
What is mass?
Mass is the amount of matter in an object.
Pan balances
Pan balances are used to compare and measure mass.
Pan balances use a center fulcrum, similar to a seesaw. They will lower/raise on one side or the other, depending on the mass of the objects they are comparing. If the objects are balanced, both sides of the scale will be equally level.
The following images display some examples of pan balances.
One side of a pan balance moves downward when an object has more mass. The pan balance stays level when the mass in both pans is equal.
Let’s examine some more pan balance examples.
The following pan balances have objects on each side. Think about the mass of the objects as you explore these pan balances.
After exploring the pan balances, answer the following questions:
- Which of the objects do you think have more mass?
- Which objects might have a similar mass?
- How do the objects compare to the apple?
- How would the pan balance react if there were two cherries on one side and a cob of corn on the other?
- How would the pan balance appear if there were a cob of corn on one side and a pineapple on the other?
- Which way does the balance tilt to show the object with more mass?
Press the ‘Answer’ button to reveal the answers.
Answer the following questions about the five pan balances:
- Do any of the objects have the same mass?
- What happens if the objects had similar mass?
- What strategies did you use to help guess which object in a pair had more mass?
Measuring mass
Standard units to measure mass are grams and kilograms, but you can use things you have nearby as a unit of measurement.
When measuring mass in a pan balance, it is best to choose non-standard units that are small, so your measurement is more accurate.
Here are some examples:
- paperclips
- dimes
- unifix cubes
Brainstorm
Let's think!
Can you think of other non-standard units to measure mass?
Teddy bear balance
Let’s explore how to measure the mass of an object with non-standard units.
The following image displays the steps of measuring the mass of a teddy bear with unifix cubes and a pan balance.
Step 1: Make sure the pan balance is balanced when empty. (Image 1 shows an empty pan
balance with both sides of the scale equally level.)
Step 2: Place the object you want to measure the mass of in one pan. (Image 2
shows a teddy bear in the left-side pan, tilted all the way down. The right-side pan
is empty and tilted up.)
Step 3: Place the units in the other pan one at a time. (Image 3 shows 3 unifix
cubes in the right-side pan, and the left side, with the teddy bear, is slightly
lower than the right.)
Step 4: Stop placing units in the pan once the pans are balanced. (Image 4
shows the teddy bear and the unifix cubes are at even heights. There are 6 unifix
cubes in the right-side pan.)
Select the correct response.
Pan-ultimate experiment
Choose four objects.
Use a pan balance to order them from lightest to heaviest.
You can sketch or describe what the pan balance would be like when you compare the masses to prove you are correct.
Press the ‘Example’ button to explore a sample response.
Sample response
I compared four objects: a backpack, a cellphone, a pencil, and a loaf of bread.
I put them in order from lightest to heaviest: pencil, cellphone, loaf of bread, backpack.
I then put the items from lightest to heaviest on pan balances.
When you are done, respond to the following questions. You can record your ideas digitally, orally, or on paper.
- Is it more precise to use units with smaller or larger mass to measure with?
- What is the benefit of using a combination of small and large units to measure the mass of an object?
Consolidation
Smallest to greatest
Consider the following items and then order them from smallest to greatest mass. Use a pan balance to order them from lightest to heaviest.
1) A book with a mass of 30 wooden cubes
2) A pencil with the mass of 5 wooden cubes
3) A marker with a mass of 6 wooden cubes
4) An apple with a mass of 10 wooden cubes
5) A water bottle with a mass of 20 wooden cubes
6) A banana with a mass of 15 wooden cubes.
You can use the following fillable and printable Smallest to Greatest document to order the objects. You can also use your notebook or another method of your choice.
Think about your learning
- If the mass of an object stays the same, how might you find different mass numbers?
- What strategies could you use to when estimating mass?
- What is important to remember when comparing the mass of different objects?
Reflection
How do you feel about what you have learned in this activity? Which of the next four sentences best matches how you are feeling about your learning? Press the button that is beside this sentence.
I feel...
Now, record your ideas about your feelings using a voice recorder, speech-to-text, or writing tool.