Materials Around Us · Lesson 6 of 7
Mass, Volume, and Matter
“Connect heavier and lighter objects with mass, occupied space with volume, and both ideas with the scientific meaning of matter.”
• Relate everyday comparisons of heavier and lighter objects to the scientific quantity called mass. • Explain volume as the space occupied by matter. • Use common units correctly for mass and volume. • Define matter using the two ideas of mass and occupied space. • Recognise solids, liquids and gases such as air as examples of matter. • Distinguish everyday use of the word weight from the mass idea introduced in this chapter.
From Heavier and Lighter to Mass
We often compare objects by saying that one feels heavier and another lighter. Science gives us a measurable property for this comparison: mass. A balance can compare or measure mass more reliably than simply lifting objects by hand.
Mass describes the amount of matter in an object. In this chapter, an object with more mass is described as heavier and one with less mass as lighter.
A simple investigation uses three identical cups filled to the same level with different materials—for example water, sand and pebbles. Because the cups and fill levels are kept comparable, weighing the cups lets us focus on how the contents affect the measured mass.
| Investigation choice | Why it matters |
|---|---|
| Use identical cups | Keeps the container itself comparable. |
| Fill to the same level | Makes the occupied cup volume similar for the comparison. |
| Predict before weighing | Encourages reasoning before measurement. |
| Use a balance | Provides a measured comparison rather than a guess by hand. |
Mass and the Word Weight
In everyday speech, people often use the word 'weight' when they are talking about mass—for example, when food is 'weighed' in a shop. At this level, the chapter focuses on mass. Mass and weight are related but are not exactly the same scientific quantity; their full relationship is studied later.
For this chapter, use mass when describing the quantity of matter. A balance reading may be casually called 'weight' in everyday language, but later science distinguishes the two quantities more precisely.
Objects and Materials Occupy Space
A school bag placed on a chair prevents a student from sitting there because the bag already occupies part of that space. Liquids also occupy space. If two identical tumblers contain different amounts of water, the higher water level shows that more space in that tumbler is occupied by water.
Volume is the amount of space occupied by matter.
The labels on bottles make this idea familiar. A bottle may contain 200 mL, 500 mL or 1 L of water or milk. These values describe volume. A container also has a capacity—the amount it can hold—so a jug of water cannot always be transferred completely into a smaller bottle.
Units for Mass and Volume
Measurements are only clear when a number is paired with the correct unit. Common mass units in this chapter are gram and kilogram. Common liquid-volume units are millilitre and litre. The SI unit of mass is kilogram, and the SI unit of volume is cubic metre.
| Quantity | Unit | Symbol | Example of correct writing |
|---|---|---|---|
| Mass | gram | g | 250 g |
| Mass | kilogram | kg | 7 kg |
| Volume | millilitre | mL | 500 mL |
| Volume | litre | L | 1 L |
| Volume | cubic metre | m³ | 2 m³ |
Unit symbols are written carefully. Use kg rather than kgs, mL with a lower-case m and upper-case L, and leave a space between the number and the unit. For cubic metre, the 3 is written as a superscript. A useful relationship is that one cubic metre equals one thousand litres.
Problem
Two identical bottles are labelled 500 mL and 1 L. Which contains the larger volume when both are full?
- 1.The first bottle contains 500 mL.
- 2.One litre is equal to 1000 mL.
- 3.Therefore, 1 L is greater than 500 mL.
- 4.The 1 L bottle contains the larger volume when both are full.
What Is Matter?
Anything that has mass and occupies space is called matter.
This definition joins the two ideas developed above. Water is matter because it has mass and occupies space. Sand, pebbles and the cup holding them are also matter. Air is matter as well: even though we usually cannot see it, air occupies space and has mass.
Materials are types of matter that are used to make objects. This connection helps separate the broad scientific idea from the everyday idea of material: all the materials discussed in the chapter are matter, but the word material is used when we focus on substances used to create objects.
Problem
Air is invisible in an ordinary room. Does invisibility mean that air is not matter?
- 1.Visibility is not part of the definition of matter.
- 2.Air occupies space—for example, it fills a balloon or an inflated tyre.
- 3.Air also has mass.
- 4.Therefore, air is matter even though we normally cannot see it.
Thinking About Materials and Society
Understanding properties also helps us think about how materials affect daily life. Plastic, for example, has enabled many light, durable and easily shaped products. At the same time, discarded plastic can remain in the environment and create waste problems. Calling a material a 'boon' or a 'bane' is therefore too simple; its value depends on how it is produced, used, reused and discarded.
Quiz
Which property is measured when we compare how much matter objects contain?
What is volume?
Which is written correctly?
Which statement best defines matter?
Why is air considered matter?
Which relationship is correct?
Practice Problems
- Explain how identical cups containing water, sand and pebbles can be used to compare mass.
- Describe the difference between mass and volume in your own words.
- Write these correctly using standard symbols: seven kilograms, five hundred millilitres, two litres and three cubic metres.
- A 1 L bottle is full and a 500 mL bottle is full. Which contains more liquid and by how much?
- Use the definition of matter to explain why water is matter.
- Use the definition of matter to explain why air is matter even though it is invisible.
- Give one benefit and one problem associated with widespread use of plastic, linking each point to a material property or use.
Key Takeaways
• Mass describes the amount of matter; a balance can be used to compare or measure it. • Volume is the space occupied by matter. • Common units include g and kg for mass, and mL and L for volume; the SI volume unit is m³. • Correct unit notation matters: write values such as 7 kg and 500 mL. • Anything that has mass and occupies space is matter. • Solids, liquids and gases—including air—can all be matter.