Mass
🎯 In this topic you will
- Estimate and measure the mass of different objects.
- Use instruments designed to measure mass accurately.
- Apply knowledge of fractions when describing mass.
🧠 Key Words
- grams (g)
- kilograms (kg)
- mass
Show Definitions
- grams (g): A metric unit used to measure small amounts of mass.
- kilograms (kg): A metric unit used to measure larger masses; 1 kilogram equals 1000 grams.
- mass: The amount of matter in an object, usually measured in grams or kilograms.
⚖️ Understanding Mass
Mass is the measure we use when we say that something is heavy or light. Sometimes an object may be too heavy to pick up, so we need tools or machines to help lift it. Mass also matters for safety — for example, planes can only take off if they are not too heavy, and lifts must stay within safe mass limits to move up and down properly.
❓ EXERCISES
$1.$ Suzie buys two peaches and four pears.
One peach weighs $80\,\text{g}$.
Four pears weigh the same as two peaches.
How much does one pear weigh?
Estimate the mass of $11$ pears before you work it out.
estimate: ________
Show how you worked out the answer.
👀 Show answer
$2.$ The chocolate bar has a mass of $100\,\text{g}$.
a. What is the mass of one muffin?
b. What is the mass of each side of the scales?
Show how you worked out the answer.
👀 Show answer
$3.$ Read the scales.
Write the mass in the boxes below.
Use $<$, $>$ or $=$ to compare the mass of each pair of objects.
👀 Show answer
$4.$ Estimate the mass of each object.
👀 Show answer
🧠 Think like a Mathematician
Task: Use these amounts to make each column or row total $1\,\text{kg}$.
$200\,\text{g}$, $250\,\text{g}$, $150\,\text{g}$, $300\,\text{g}$, $400\,\text{g}$, $500\,\text{g}$, $450\,\text{g}$, $700\,\text{g}$, $50\,\text{g}$
Instructions:
- Place the given masses into the grid.
- Arrange them so that every row or every column adds up to $1000\,\text{g}$.
- Check each total carefully.
Challenge: Use these amounts to make columns and rows that total $1\,\text{kg}$.
$500\,\text{g}$, $250\,\text{g}$, $50\,\text{g}$, $450\,\text{g}$, $150\,\text{g}$, $600\,\text{g}$, $250\,\text{g}$, $350\,\text{g}$, $400\,\text{g}$
Follow-up Question:
How many different ways can the total of $1\,\text{kg}$ be found?
👀 show answer
- You are looking for combinations that add to $1000\,\text{g}$.
- Examples from the first set include: $700+300$, $500+450+50$, $400+250+150+200$.
- In the challenge set, examples include: $600+400$, $500+350+150$, $450+250+250+50$.
- There is more than one correct arrangement — several different combinations can make $1\,\text{kg}$. The exact number depends on how many unique groupings you find without repeating the same set in a different order.