Chapter 3 · P4 Science
⚗️ Matter
📚 Section A — Revision Notes

What I Will Learn

  • Define matter and give examples of matter and non-matter
  • Name the three states of matter and compare their properties
  • Describe how to measure mass and volume correctly
  • Explain how to conduct a fair scientific investigation
1
What Is Matter?
Matter — anything that has mass and occupies space.
  • Examples of matter all around us: stones, water, air, living things.
  • Anything that does not have mass or does not occupy space is not matter — we call this non-matter. Examples: light, heat, sound and shadows.
🎯 Get It Right!
❌
Wrong concept: Air is not matter because we cannot see it.
✅
Correct concept: Not all matter is visible. Air is matter — it has mass and occupies space, even though we cannot see it.
⚖️ Mass
Mass — the amount of matter in an object. Objects with more matter have a greater mass.
  • Mass is measured using a balance or an electronic balance.
  • Mass is recorded in grams (g) or kilograms (kg).
  • We can show that air has mass by comparing an inflated ball with a deflated ball on a balance — the inflated ball tilts the balance, showing it has greater mass.
💡 Did You Know?
Mass and weight are not the same thing. Mass is the amount of matter in an object. Weight is a force that depends on gravity. You will learn more about weight in Primary 6.
📐 Volume
Volume — the amount of space an object occupies. Objects that take up more space have a greater volume.
  • Volume is measured using a measuring cylinder or a beaker.
  • We can show that air occupies space by pushing an upturned glass into water — water cannot fully enter because the air inside already takes up the space.
Air occupies space experiment A glass pushed into water — water cannot enter fully because air occupies the space inside Air Occupies Space glass water Before → air After (air blocks water)
▲ Air inside the glass prevents water from entering — showing air occupies space
📋 Checkpoint 3.1

1. What is matter?

  • Matter is anything that has mass and occupies space.
  • Examples: stones, water, air
  • Non-matter (no mass, no space): light, heat, sound, shadow
2
States of Matter and Their Properties
  • Matter can be sorted by physical properties such as colour, shape, size and material — or by how those properties change.
  • Matter exists as a solid, a liquid or a gas. We call these the three states of matter.
🪨 Solid State
Solid — matter with a definite shape AND a definite volume.
  • A solid does not take the shape of its container — it keeps its own shape.
  • A solid has a definite volume, so it cannot be compressed.
  • Examples: stones, books, pens.
💧 Liquid State
Liquid — matter with no definite shape but a definite volume.
  • A liquid takes the shape of its container — pour it into any vessel and it fills the shape.
  • Because it has a definite volume, a liquid cannot be compressed.
  • Examples: water, milk, oil.
💨 Gaseous State
Gas — matter with no definite shape AND no definite volume.
  • A gas takes the shape of its container.
  • Because it has no definite volume, a gas can be compressed.
  • Examples: oxygen, carbon dioxide, hydrogen.
🎯 Get It Right!
❌
Wrong concept: A sponge is not a solid because it can be compressed.
✅
Correct concept: A sponge IS a solid. It has many holes filled with trapped air. When we squeeze it, we push the air out of the holes — making it appear compressed. We are not actually compressing the sponge material itself.
📋 Comparing the Three States
PropertySolidLiquidGas
ShapeDefinite shapeNo definite shape (takes shape of container)No definite shape (takes shape of container)
VolumeDefinite volumeDefinite volumeNo definite volume
Compressible?Cannot be compressedCannot be compressedCan be compressed
Particle arrangement in solids, liquids and gases Closely packed particles in solid, less tightly packed in liquid, widely spread in gas Particle Arrangement Solid tightly packed Liquid less tightly packed Gas very loosely packed
▲ Particles are most tightly packed in solids, less so in liquids, and very spread out in gases
💡 Did You Know? — Particle Theory
All matter is made up of extremely tiny particles. In a solid, particles are packed tightly together — they can’t move around, so the solid keeps its shape. In a liquid, particles are close but can slide past each other, so it flows. In a gas, particles are very far apart and move freely, so a gas spreads out and fills whatever container it’s in.
📋 Checkpoint 3.2

1. State one difference between a solid and a liquid.

2. State one difference between a liquid and a gas.

  • Q1: A solid has a definite shape, while a liquid has no definite shape (it takes the shape of its container). / A solid cannot be compressed; a liquid also cannot be compressed — so the key difference is shape.
  • Q2: A liquid has a definite volume and cannot be compressed, while a gas has no definite volume and can be compressed.
⚙️ Worked Example 3.1

An air-tight container has a total volume of 100 cm³. It currently contains 75 cm³ of air and 25 cm³ of water.

(a) Sasha pumps 10 cm³ of water into the container. What will be the volume of air?

(b) She then pumps 10 cm³ of air into the container. What is the final volume of air?

Air-tight container experiment Container with 75 cm3 air and 25 cm3 water, with a pump inlet air 75 cm³ water 25 cm³ pump inlet Total volume = 100 cm³
▲ Air-tight container with 75 cm³ air + 25 cm³ water

(a) 65 cm³

  • Water is pumped in → water cannot be compressed, so it takes up the space of its full volume.
  • New total water = 25 + 10 = 35 cm³
  • Air can be compressed to make room. Volume of air = 100 − 35 = 65 cm³

(b) Still 65 cm³

  • The extra 10 cm³ of air is compressed into the existing air space.
  • Water still takes up 35 cm³ (it cannot be compressed).
  • The volume of air stays at 65 cm³ — the new air is simply compressed to fit.
3
How Are Mass and Volume Measured?
⚖️ Measuring Mass — Electronic Balance
  • Mass is measured with an electronic balance (or a traditional balance). It is recorded in grams (g) or kilograms (kg).
🪨 Mass of a Solid
  • Place the electronic balance on a flat surface — this ensures an accurate reading.
  • Press the ‘ON’ button before placing anything on the pan.
  • The reading must show zero. If not, press ‘Tare’ or ‘Zero’ to reset.
  • Place the solid on the measuring pan.
  • The reading shown is the mass of the solid.
💧 Mass of a Liquid
  • A liquid has no definite shape — it cannot be placed directly on the pan. It must be put into a container first.
  • Set up the balance on a flat surface and press ‘ON’. Confirm zero reading.
  • Place an empty container on the pan. Record its mass.
  • Pour the liquid into the container. Record the total mass.
  • Mass of liquid = total mass − mass of container
Measuring mass of a liquid 50 g empty beaker = 50 g 100 g beaker + water = 100 g → Mass of liquid = 100 g − 50 g = 50 g
💨 Mass of a Gas
  • Like a liquid, a gas has no definite shape. It must be placed in a container such as a balloon or ball.
  • Set up the balance on a flat surface and press ‘ON’. Confirm zero reading.
  • Place the deflated container (e.g. deflated balloon) on the pan. Record its mass.
  • Fill the container with gas. Record the total mass.
  • Mass of gas = total mass − mass of empty container
⚖️ Using a Traditional Balance
  • Place the object on one pan. Add fixed masses to the other pan until the two pans are level — this is when the masses are equal.
  • A balance also compares masses directly: it tilts towards the heavier side.
📐 Measuring Volume
  • Volume is measured using a measuring cylinder, beaker or measuring cup.
  • A measuring cylinder gives a more accurate reading than a beaker.
  • Volume is recorded in cm³, m³, ml or litres (l). Note: 1 cm³ = 1 ml.
💧 Volume of a Liquid — Reading the Meniscus
  • Place the measuring cylinder on a flat surface.
  • Pour the liquid in. The surface may look curved — this curved surface is called the meniscus.
  • Place your eye at the same level as the bottom of the curved surface. Read the volume from the bottom of the meniscus.
Reading the meniscus in a measuring cylinder 80 60 50 40 eye level bottom of meniscus Volume = 50 cm³
▲ Eye at same level as the bottom of the meniscus — read 50 cm³
🪨 Volume of a Solid — Displacement Method
  • Place the measuring cylinder on a flat surface.
  • Pour in some water and record the initial water level.
  • Tie a string to the solid and gently lower it into the cylinder. Ensure no water spills out.
  • Record the new water level.
  • Volume of solid = new water level − initial water level
💡 Did You Know? — Displacement Can
The volume of a solid can also be found using a displacement can. Lower the solid (on a string) into the full can. Water overflows through the spout into a measuring cylinder — the volume of that water equals the volume of the solid.
💨 Volume of a Gas
  • Fill a measuring cylinder completely with water. Invert it into a basin of water — no air must enter.
  • Blow air into the inverted cylinder through a straw. The air pushes an equal volume of water out.
  • Read the volume on the measuring cylinder — this is the volume of air.
📋 Checkpoint 3.3

1. How can we measure the mass of water in a cup?

2. Name one instrument that can measure the volume of both a liquid and a gas.

  • Q1: Use an electronic balance. First record the mass of the empty cup. Then pour the water in and record the total mass. Mass of water = total mass − mass of empty cup.
  • Q2: A measuring cylinder can measure the volume of both a liquid and a gas.
4
How to Conduct a Scientific Investigation
  • Curiosity about the world leads to questions. Scientists design investigations to find answers.
  • Before an investigation, scientists form a hypothesis — a prediction of what they think will happen.
  • The investigation is designed to test the hypothesis.
Variables — things that can be changed in an experiment. Every investigation has three kinds:
  • Variable to be changed — the one factor you deliberately alter (the independent variable).
  • Variable to be measured — what you observe or record as a result (the dependent variable).
  • Variables to keep constant — everything else that must stay the same so the test is fair.
Fair test — an investigation where only one variable is changed at a time. All other variables are kept constant.
🔬 Example Investigation
QuestionDoes the size of an object affect its volume?
HypothesisA bigger object has a greater volume.
Variable to changeSize of the object
Variable to measureVolume of the object
Variables to keep constantMaterial of the object; measuring cylinder used; initial volume of water; location of experiment
ResultThe bigger pebble had a greater volume.
ConclusionA bigger object has a greater volume — this supports the hypothesis.
💡 Exam Tips — Experiments
  • Always use the correct instrument and take measurements carefully — this makes results accurate.
  • Repeat the experiment several times — repeated results are reliable.
  • If results do not support the hypothesis, that is fine — change the hypothesis and repeat.
📋 Checkpoint 3.4

1. What is a hypothesis?

2. How many variables should be changed in a fair test?

  • Q1: A hypothesis is a statement of what you predict will happen in your investigation.
  • Q2: Only one variable should be changed in a fair test. All other variables must be kept constant.

📌 Chapter Summary

  • Matter = anything with mass and that occupies space. Non-matter (light, heat, sound, shadow) has neither.
  • Air is matter — it has mass and occupies space even though we can’t see it.
  • Solid: definite shape and volume; cannot be compressed.
  • Liquid: no definite shape, definite volume; cannot be compressed; takes shape of container.
  • Gas: no definite shape or volume; can be compressed; takes shape of container.
  • A sponge is a solid — squeezing it expels trapped air from holes, not compressing the material.
  • Mass → measured by electronic balance or balance with fixed masses; units: g or kg.
  • For liquids and gases: mass = (mass of container + substance) − (mass of empty container).
  • Volume → measured by measuring cylinder (most accurate), beaker or measuring cup; units: cm³, ml, l.
  • Volume of solid → displacement method: new water level − initial water level.
  • Always read the volume from the bottom of the meniscus, with eye at the same level.
  • Fair test: only ONE variable is changed; all others stay constant.
  • Repeat experiments for reliability; use correct instruments for accuracy.
✏️ Practice Questions — MCQ
1. Which of the following is an example of non-matter?
✅ Correct! Light has no mass and does not occupy space — it is non-matter. Water, air and stone all have mass and occupy space, so they are all matter.
❌ Light is non-matter — it has no mass and does not occupy space. Water, air and stone are all matter, even though air is invisible.
2. A sponge can be squeezed so that it becomes smaller. Does this mean a sponge is NOT a solid?
✅ Correct! A sponge is a solid. It has many holes filled with trapped air. Squeezing it forces the air out — but the solid material itself is not compressed.
❌ A sponge IS a solid. It appears to compress because the air trapped in its holes is pushed out. The solid material of the sponge is not actually being compressed.
3. Which state of matter can be compressed?
✅ Correct! Only gases can be compressed — they have no definite volume. Solids and liquids both have definite volumes and cannot be compressed.
❌ Only gases can be compressed. Both solids and liquids have definite volumes and cannot be compressed.
4. Kylie measures the mass of a liquid. The empty beaker reads 40 g. After pouring the liquid in, the balance reads 95 g. What is the mass of the liquid?
✅ Correct! Mass of liquid = total mass − mass of container = 95 − 40 = 55 g.
❌ Mass of liquid = total mass − mass of empty container = 95 − 40 = 55 g.
5. When measuring the volume of a liquid using a measuring cylinder, where should you read the scale?
✅ Correct! Always read from the bottom of the meniscus with your eye at the same level as the liquid surface, to get an accurate reading.
❌ The correct method is to place your eye at the same level as the liquid surface and read from the bottom of the curved surface (meniscus).
6. A stone is placed in a measuring cylinder containing 50 cm³ of water. The water level rises to 80 cm³. What is the volume of the stone?
✅ Correct! Volume of stone = new water level − initial water level = 80 − 50 = 30 cm³.
❌ Volume of solid = new water level − initial water level = 80 − 50 = 30 cm³. This is the displacement method.
7. In a fair test to investigate whether the size of an object affects its volume, which is the variable to be CHANGED?
✅ Correct! The variable being investigated — the size of the object — is the one that must be changed. All others must be kept constant.
❌ The variable being tested is always the one to change. Here, we are testing size, so size must differ between trials. Everything else stays the same.
8. Which instrument gives the MOST accurate measurement of the volume of a liquid?
✅ Correct! A measuring cylinder gives the most accurate volume reading. A beaker and measuring cup are less precise. An electronic balance measures mass, not volume.
❌ The measuring cylinder is the most accurate volume instrument. A beaker has broader graduations, a measuring cup is for cooking, and a balance measures mass — not volume.
9. To make sure experimental results are reliable, what should a scientist do?
✅ Correct! Repeating an experiment several times confirms the results are consistent and reliable.
❌ To ensure reliability, the experiment should be repeated several times. This confirms the results are consistent, not just a one-off outcome.
10. An air-tight container has a volume of 120 cm³. It holds 90 cm³ of air and 30 cm³ of water. If 20 cm³ of air is let out, what is the new volume of air in the container?
✅ Correct! When 20 cm³ of air is let out, the air that remains expands back to its uncompressed volume. The water volume stays at 30 cm³. Air volume = 120 − 30 = 90 cm³… wait — actually when air is released, the pressure drops and remaining air expands to fill: 90 − 20 = 70 cm³ of air remains.
❌ When 20 cm³ of air is released, the remaining air volume = 90 − 20 = 70 cm³. The water remains at 30 cm³ (it cannot be compressed or expanded).
✏️ Practice Questions — Open-Ended
1. Describe an experiment to show that air has mass. [2]
Use a balance with an inflated ball on one pan and a deflated ball on the other. The balance will tilt towards the inflated ball, showing it has greater mass. Since the only difference between the two balls is the air inside the inflated one, we can conclude that air has mass.
2. State the difference between a liquid and a gas in terms of shape, volume and compressibility. [3]
  • •Shape: Both a liquid and a gas have no definite shape — they take the shape of their container.
  • •Volume: A liquid has a definite volume, while a gas does not have a definite volume.
  • •Compressibility: A liquid cannot be compressed, while a gas can be compressed.
3. Explain why a measuring cylinder is preferred over a beaker when measuring the volume of a liquid. [2]
A measuring cylinder gives a more accurate reading than a beaker. This is because a measuring cylinder has smaller, more precisely spaced graduations, allowing for a more exact measurement of the liquid’s volume.
4. Kylie placed a marble in a measuring cylinder. She then poured 35 ml of water into the cylinder. The water level read 40 ml.
(a) What is the volume of the marble? [1]
(b) Which property of water allows Kylie to use this method? [1]
(a) Volume of marble = 40 ml − 35 ml = 5 ml (or 5 cm³)

(b) Water has a definite volume (and cannot be compressed). This means the water level rises by exactly the volume of the marble when it is submerged.
5. Sam wants to find out whether the shape of an object affects its mass. He has three objects of the same material and the same size but different shapes.
(a) State the variable to be changed. [1]
(b) State TWO variables to be kept constant. [2]
(a) Variable to be changed: The shape of the object.

(b) Two variables to keep constant (any two of):
  • •The material the object is made of
  • •The size of the object
  • •The electronic balance used
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