Minds On
Comparing mass
Examine the following examples of scales. Each of the scales is imbalanced.
Which side is heavier? Which side is lighter?
What could you do to make the scale evenly balanced?
Record your ideas in a notebook or a method of your choice.
Using a scale to compare mass
Find two items around your environment. If possible, lift each item.
- Which one is heavier?
- Which one is lighter?
- What do you think would happen if you put the two items on a scale?
Mass is the amount of matter that makes up an object. An object with a greater mass would be heavier if you compare it to an object with a lighter mass. A scale would show you which object has a larger mass if you put one object on each side of the scale.
Using the examples from the Comparing mass section, answer the following:
- Which has a larger mass, the apple or the grape?
- Which has a smaller mass, the small wooden car or the larger remote-controlled car?
Record your ideas in a notebook or a method of your choice.
Action
Task 1: Defining mass
What is mass? Mass refers to the amount of matter that is in an object.
Fun fact!
Mass and weight are not the same thing!
While an object’s weight is caused by the effects of gravity, an object’s mass will not change unless part of the object is changed.
For example, imagine we put a car on Mars. If we put the same car on another planet, the weight would change (thanks gravity!). However, the mass of the car would not change.
The reason that weight and mass appear to be the same thing is because everything we are measuring is on Earth has a gravitational pull. Therefore, mass is the amount of matter in an object.
Research the difference between a scale and a balance.
- Which is the most accurate way to measure mass?
- Using a scale or a balance?
- Why is this?
Record your ideas in a notebook or a method of your choice. When you are ready, press the ‘Show Answer’ button to reveal an explanation.
Task 2: Using metric units to measure mass
Mass is measured using metric measurements such as milligrams, grams, and kilograms.
The following table explains the relationship between metric units.
| Kilo | Hecto | Deka/Deca | (Unit) | Deci | Centi | Milli |
|---|---|---|---|---|---|---|
| Kilometre | Hectometre | Dekametre | Metre | Decimetre | Centimetre | Millimetre |
| Kilogram | Hectogram | Dekagram | Gram | Decigram | Centigram | Milligram |
| Kilolitre | Hectolitre | Dekaliter | Litre | Decilitre | Centilitre | Millilitre |
Scavenger hunt!
If possible, find or think of objects in real-life that might have the following masses:
- 1 gram
- 4 grams
- 50 grams
- 1 kilogram
- 2 kilograms
- 10 kilograms
Now determine which metric measurement (milligrams, grams, or kilograms) would be appropriate to measure the mass of each object. Complete the Mass Scavenger Hunt table in your notebook or using the following fillable and printable document. You can also use a method of your choice.
Using the Mass Scavenger Hunt table, which unit would make the most sense for measuring the objects? Explain your reasoning.
| Milligram | Grams | Kilograms |
|---|---|---|
Press the ‘Activity’ button to access Mass Scavenger Hunt.
If you are having trouble finding objects in your surroundings for this activity, then think about the following objects.
- a paperback book
- a watermelon
- a piece of gum
- an apple
- one litre of water
- a microwave
- a stuffed animal
- a feather
Which unit would make the most sense for measuring them? Explain your reasoning.
Use the same Mass Scavenger Hunt table, or record your ideas in a notebook. You can also use another method of your choice.
Use the Mass Scavenger Hunt Solutions button to check your work.
Task 3: Converting units of measure
Using this information, brainstorm how you might convert between mg, g, and kg.
- 1 gram = 1,000 milligrams
- 1 kilogram = 1,000 grams
The following diagram illustrates how to convert between different units!
Now it’s time to practice!
For the following questions, record your answers in a notebook or a method of your choice.
For the first four questions, you will convert the units. Convert the following:
Question 1) 7 kg into g
Question 2) 2.5 g into mg
Question 3) 1 mg into g
Question 4) Go back to task 2 and choose at least 3 of the objects that you found and convert them to all other units of measure.
After answering the questions in your notebook, press the ‘Show Answer’ button to reveal the solutions.
Solution 1) We know that 1 kg is 1,000 grams. Therefore, we would multiply 1,000 × 7 = 7,000 g.
Solution 2) We know that 1 gram is 1,000 milligrams.
Therefore, we would multiply 2.5 × 1,000 = 2,500 mg.
Solution 3) We know that 1,000 mg is 1 gram and 1,000 g is 1 kg.
Therefore, we can divide 1 ÷ 1,000 = 0.001 g.
Solution 4) Sample Response: I know that 1 paper clip is equal to 1 gram.
Therefore:
1 ÷ 10 = 0.1 dekagrams–1 paperclip equals 0.1 dekagrams.
0.1 ÷10 = 0.01 hectograms–1 paperclip equals 0.01 hectograms.
0.01 ÷ 10 = 0.001 kilograms–1 paperclip equals 0.001 kilograms.
1 × 10 = 10 decigrams–1 paper clip equals 10 decigrams.
10 × 10 = 100 centigrams–1 paperclip equals 100 centigrams.
100 × 10 = 1,000 milligrams–1 paperclip equals 1,000 milligrams.Now answer each mass comparison.
Question 5) What has more mass? An object that has a mass of 1,500 grams or 1 kilogram?
Question 6) What has more mass? An object that has a mass of 40,000 mg or 4,000 g?
After answering the questions in your notebook, press the ‘Show Answer’ button to reveal the solutions.
Solution 5) 1,000 grams = 1 kilogram, therefore 1,500 grams would be 1.5 kilograms.
Therefore, object of 1,500 grams has more mass than an object of 1 kilogram.
Solution 6) 1 gram = 1,000 mg
40,000 ÷ 1,000 = 40
40,000 mg is equal to 40 grams.
Therefore, an object with a mass of 4,000 grams has the greater mass of the two objects.Task 4: Word problems
Scenario 1
1) Here are the items a chef needs for an event.
Using this information complete the following word problem.
Record your ideas in a notebook or a method of your choice.
a) The chef only has a little space left in the car, so they can only add 6 kg of food. What items should they choose?
b) Sort the items chosen from the least mass, to the highest mass.
c) Now look at all the items (including the items you did not choose). Add up all of the items to find the total mass in kg. Convert the total into grams and then into milligrams.
After answering the questions in your notebook, press the ‘Show Answer’ button to reveal the solutions.
a) The chef could choose rice (1,000 g), potatoes (2,000 g), apples (1.7 kg), and bananas (1.3 kg). I know this adds up to 6 kg because of the relationship 1,000 g = 1 kg.
b) Rice, bananas, apples, and potatoes.
c) I know that 1,000 g = 1 kg and 10,000mg = 1 kg
Rice – 1,000 g = 1 kg
Potatoes – 2,000 g = 2 kg
Apples – 1.7 kg
Bananas – 1.3 kg
Bag of grapes – 700 g = 0.7 kg
Bag of parsnips – 1.5 kg
Samosas – 500 g = 0.5 kg
Shredded Cheese = 1 kg
1 + 2 + 1.7 + 1.3 + 0.7 + 1.5 + 0.5 + 1 = 9.7kg
9.7 kg = 9,700 g = 9,700,000 mg
Scenario 2
Some gardeners are going to work outside. They have a bag with items that have a mass of 14.2 kg. They must include the compost bag, which is 2.4 kg. Use the following criteria to figure out which other items are in the bag.
The criteria:
- There are 6 items in total.
- 1 item is the compost bag. It has a mass of 2.4 kg and is half the weight of the heaviest item.
- 1 of the items has a mass of 1,000 g.
- Two items have the same mass. Together they are 3,000 g.
- The last item in the bag has a mass of 30,000 mg.
Which of the following items are in the gardener’s bag? Explain your thinking. Record your ideas in a notebook or a method of your choice.
- Shovel – 1 kg
- Food – 3 kg
- Water – 4.8 kg
- Book – 1.1 kg
- Seeds – 10 g
- Compost bags – 2.4 kg
- Rake – 1.5 kg
- Gloves – 1.5 kg
After answering the questions in your notebook, press the ‘Show Answer’ button to reveal the solutions.
We are given that we must include the compost bag, which is 2.4 kg. I know that 1,000 g = 1 kg and the only item in the list that is exactly 1 kg is the shovel.
I know that two items added together have a mass of 3,000 g. 3,000 g = 3 kg, and 3 kg split in half is 1.5, therefore I know that those items are the rake and gloves.
If 2.4 kg is the mass of half the weight of the heaviest item, this item must be water because 4.8 kg ÷ 2 = 2.4 kg.
I know that the last item in the bag is 30,000 mg. I know that 10,000 mg = 1 kg which means that 30,000 mg = 3 kg. The last item is food.
Shovel – 1 kg
Food – 3 kg
Water – 4.8 kg
Compost bags – 2.4 kg
Rake – 1.5 kg
Gloves – 1.5 kg
All six items are summed together: 1 + 3 + 4.8 + 2.4 + 1.5 + 1.5 = 14.2 kg
Consolidation
What should the photographer pack?
A wildlife photographer is going on an expedition. They only have 1 suitcase and have decided the maximum mass they can carry is 10.5 kg. They will carry their camera separately.
For the purpose of deciding what to bring, the photographer calculated the mass of the liquids (water, bug repellant, and sunscreen) which are normally measured in mL.
Their list of possible items includes:
- Food: 3.2 kg
- Water: 4,000 g
- Bug repellant: 230,000 mg
- Clothes: 1 kg
- Foldable tent: 7 kg
- Extra blanket: 1,000 g
- Sunscreen: 170 g
- What items could the photographer bring?
- Determine the average weight of the items using the following units of measure: mg, g, and kg.
- Now, complete this task once again. This time, keep in mind that the suitcase itself (when empty) has a mass of 2 kg.
Record your ideas in a notebook or a method of your choice.
Thinking back
Reflect and respond to the following questions:
- Why is it important to understand the difference between weight and mass?
- When would mass be something you need to know about in your daily life?
Record your ideas in a notebook or a method of your choice.
Reflection
As you read through these descriptions, which sentence best describes how you are feeling about your understanding of this learning activity? Press the button that is beside this sentence.
I feel...
Now, record your ideas using a voice recorder, speech-to-text, or writing tool.
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