States of Matter (P4 Lesson and Worksheet)

Look around you. Your desk, the water in your bottle, and the air around you are all matter.

What is matter?

Matter is anything that has mass and occupies space. That means:

• • Mass: you can weigh it.

• • Occupies space: it takes up room (even if you cannot see it).

Quick check (critical thinking):

Question: If you cannot see something, does it mean it is not matter?

Answer: No. Air is matter because it has mass and takes up space.

The 3 states of matter

Matter can be in 3 main states:

1. 1. Solid

1. 1. Liquid

1. 1. Gas

We compare them using shape and volume.

1) Solids: fixed shape, fixed volume

A solid has:

• • Fixed shape (keeps its shape)

• • Fixed volume (keeps the same amount of space)

• • Cannot be compressed (it is very hard to squash)

Examples:

• • book, pencil, rock, ice cube

Let’s think!

Question: If you move a solid into a different container, will it change shape?

Answer: No. A solid does not take the shape of the container.

2) Liquids: no fixed shape, fixed volume

A liquid has:

• • No fixed shape (it changes shape)

• • Fixed volume (same amount of liquid)

• • Cannot be compressed (it is very hard to squash)

Examples:

• • water, juice, milk

If you pour water from a bottle into a cup:

• • the shape changes

• • the volume stays the same (same amount of water)

• • it cannot be compressed easily (even if you press or squeeze it, the water does not “squash” into a smaller volume)

Let’s think!

Question: If a liquid changes shape, does that mean its volume changes too?

Answer: No. If no liquid is spilled, the volume remains the same even though the shape changes to fit the container.

3) Gases: no fixed shape, no fixed volume

A gas has:

• • No fixed shape

• • No fixed volume

• • Can be compressed easily (it can be squeezed into a smaller space, e.g., in a syringe or pump)

A gas spreads out to fill all the space it has. Examples:

• • air, oxygen, water vapour

Let’s think!

Question: Why does a gas “disappear” when released?

Answer: It does not disappear. The gas spreads out to fill the space and mixes with the surrounding air, so it becomes too spread out to see.

Compare the states of matter

State	Shape	Volume	Can be compressed?
Solid	Fixed	Fixed	No
Liquid	Not fixed	Fixed	No
Gas	Not fixed	Not fixed	Yes

Measuring matter: mass and volume

Mass

• • Measured using a balance.

Volume

• • For liquids: use a measuring cylinder.

• • For solids:
    • • If it is a regular shape, you can measure using a ruler (in some cases).
    • • If it is an irregular shape (like a stone), use water displacement:
        1. 1. Put water in a measuring cylinder and record the volume.
           2. Carefully drop the solid in.
           3. Record the new volume.
           4. Volume of solid = new volume − old volume

Let’s think!

Question: Why does the water level rise when you add a solid?

Answer: The solid occupies space. When it is placed into the water, it displaces the water (pushes the water aside), so the water level rises.

 

🧠 Critical thinking practice (mini challenge)

1. 1. Is air matter? Yes/No because ________________________.

1. 1. You pour juice into a taller cup. The juice looks “more.” Is the volume really more? Yes/No because ________________________.

1. 1. A balloon gets bigger when you blow it up. What is filling the balloon? Is it matter? Why? ________________________.

Key takeaways

• • Matter has mass and occupies space.

• • Solids: fixed shape, fixed volume, cannot be compressed.

• • Liquids: no fixed shape, fixed volume, cannot be compressed.

• • Gases: no fixed shape, no fixed volume, can be compressed.

• • We measure mass with a balance and volume using tools like a measuring cylinder (and water displacement for irregular solids).

Ready to test yourself?

Grab your Primary 4 States of Matter Worksheet and try the questions.