Find your next learning step
Start with the difficulty closest to yours, then work through an example and try the practice independently.
Open the complete guide contents
To compare solids, liquids and gases, ask two separate questions: does the substance keep its shape, and does it keep its volume? A liquid can change shape without changing the amount of space occupied by that quantity. Keeping shape and volume separate is the main learning step.
This guide helps Primary 4 pupils explain matter with clear observations and original examples. Begin with familiar substances such as a wooden block, water and air. Avoid judging a substance only by whether it pours or whether you can see it.
MOE's 2023 Primary Science syllabus includes P4 matter. This guide concentrates on mass, occupied space, shape and volume. It is a focused study sequence, not an exhaustive syllabus or a guide to unsupervised heating experiments.
Matter has mass and occupies space. A wooden block is matter. Water is matter. Air is also matter even though we usually cannot see it. Visibility is not the deciding test.
An empty-looking bottle may contain air. Calling it “empty” in everyday speech usually means there is no drink inside, not that there is no matter inside. In Science, name the substance being discussed.
Light is not classified as matter in this primary-school treatment. It is not enough to say that something is present or noticeable; use the defining properties. The aim is a consistent classification rather than a list of familiar examples.
Mass describes the amount of matter in an object. Volume describes the space it occupies. An object's mass is commonly recorded in grams or kilograms, while liquid volume may be recorded in millilitres or litres.
Do not use the words interchangeably. A reading of 200 mL describes a volume, not a mass of 200 g. Water under ordinary conditions may make those numbers look conveniently related, but the relationship cannot be applied to every substance.
If a question asks how much space something occupies, discuss volume. If it asks about mass, use an appropriate mass measurement. The question and the unit help identify the quantity.
For ordinary classroom comparisons, a solid has a definite shape and volume. A liquid has a definite volume but takes the shape of the part of its container that it occupies. A gas has neither a definite shape nor a definite volume; it spreads to fill the available space in its container.
A wooden block moved from a bowl to a box keeps its shape. Water poured from a wide cup into a narrow cup changes shape. Air transferred into a different enclosed container occupies that container's available space.
These descriptions concern the states under the stated conditions. Solids can be cut, bent or squeezed, but being able to change an object's shape by applying a force does not make it a liquid.
An original practice question gives 100 mL of water in a wide cup. All of it is poured into a narrower cup, with none spilt and no water added. Does the volume increase because the water level is higher?
No. The volume remains 100 mL. The narrower container needs a taller column of water to hold the same volume. The shape and water level change, while the volume of the transferred water remains the same under the given conditions.
Do not answer by height alone. Ask what happened to the water: was any added, removed or spilt? The description explicitly says all of it was transferred. That information is essential to the conclusion.
A sealed bag containing air can become puffed out because the air occupies space. If the bag changes shape, the air inside follows the available space. This supports the idea that air is a gas, not an absence of matter.
The air in an ordinary room is a mixture of gases. For this level, focus on the properties relevant to the question rather than adding a complicated account of every component.
If a drawing shows an unsealed container, do not assume all the original air remains trapped. Read whether the system is open or closed. A conclusion about a fixed quantity of gas requires conditions that actually keep that quantity inside.
Sand can be poured, but each grain is solid. A collection of grains changes its overall arrangement and can fit the shape of a container, yet pouring the collection does not turn the grains into a liquid.
Similarly, flour and rice can flow as collections of small solid pieces. Ask about the individual pieces, then about their arrangement. The visible movement of a collection is not by itself a reliable test of a liquid state.
Softness is also not the deciding property. A sponge is a solid object even though it can be squeezed. Keep the explanation on the relevant properties instead of replacing them with “hard”, “soft” or “can pour”.
- Name the two defining properties of matter.
- Water is transferred without loss into a differently shaped cup. Which may change: shape or volume?
- A bag contains air that cannot escape. Is the air matter?
- Rice grains can be poured. Does that make the grains liquid?
- What quantity is described by 250 mL?
Answers: 1. It has mass and occupies space. 2. The shape changes to fit the new container; the volume remains the same under these conditions. 3. Yes; air has mass and occupies space. 4. No; the grains are solids. 5. Volume.
For question 2, include the condition “without loss”. If water spills during the transfer, the volume remaining in the new cup will be smaller. A clear explanation respects the supplied conditions.
Compare a stone, cooking oil and air using shape and volume. Under ordinary classroom conditions, the stone is solid, oil is liquid and air is gas. Ask the child to explain each choice with properties rather than the object name alone.
If shape and volume remain confused, use two cups and an imagined transfer with an explicitly fixed amount. If invisible substances are rejected as matter, return to the air example. If pourable solids are misclassified, discuss one grain and the collection separately.
Parents can ask, “What changed, and what stayed the same?” That question is a useful bridge from observation to explanation. The child is ready to continue when those two answers remain clear in a new situation.