Science · 4th Grade · States of Matter and Their Changes · Weeks 28-36

Properties of Solids, Liquids, and Gases

Observe and describe the distinct properties of matter in its solid, liquid, and gaseous states.

• Common Core State Standards
• 2-PS1-1

About This Topic

Matter exists in three familiar states -- solid, liquid, and gas -- and each has distinct, observable properties that students can investigate directly. Fourth graders learn to describe solids by their definite shape and volume, liquids by their definite volume but changeable shape, and gases by their ability to fill any container completely. Standard 2-PS1-1 asks students to observe and describe these differences using evidence from hands-on investigations.

This topic builds the conceptual foundation for later work on particle models and phase changes. In the US curriculum, 4th graders approach states of matter primarily through observation and description, not through particle theory -- though skilled teachers can introduce informal particle language to prepare students for later grades.

Active learning helps here because states of matter are easy to observe but surprisingly tricky to define precisely. When students handle ice, water, and steam (or air in a balloon), they confront edge cases -- is whipped cream a solid or a liquid? -- that sharpen their definitions. Discussion of these boundary cases is more effective at building precise understanding than reading a definition from a book.

Key Questions

1. Differentiate the observable properties of solids, liquids, and gases.
2. Analyze how the arrangement of particles differs in each state of matter.
3. Predict how a substance's properties might change if its state changes.

Learning Objectives

• Classify common substances as solids, liquids, or gases based on observable properties.
• Compare and contrast the properties of shape and volume for solids, liquids, and gases.
• Explain how the ability of a substance to fill a container differs between solids, liquids, and gases.
• Analyze evidence from hands-on investigations to describe the distinct properties of each state of matter.

Before You Start

Observing and Measuring

Why: Students need to be able to make careful observations and record measurements to describe the properties of different states of matter.

Basic Properties of Objects

Why: Understanding concepts like shape and size is foundational for describing the more complex properties of volume and how matter fills containers.

Key Vocabulary

Solid	A state of matter that has a definite shape and a definite volume. Its particles are tightly packed.
Liquid	A state of matter that has a definite volume but takes the shape of its container. Its particles can move past each other.
Gas	A state of matter that has no definite shape and no definite volume; it fills its entire container. Its particles are far apart and move freely.
Volume	The amount of space that a substance or object occupies. Liquids and gases have volumes that can change depending on the container.

Watch Out for These Misconceptions

Common Misconception

All solids are hard and all liquids flow quickly.

What to Teach Instead

Solids can be soft (foam, clay) and still be solids because they hold their shape without a container. Liquids can flow very slowly (honey, ketchup) and still be liquids. Sorting activities with non-typical examples surface these misconceptions quickly and give students evidence to revise their thinking.

Common Misconception

Gases are not matter because you cannot see or hold them.

What to Teach Instead

Gases have mass and take up space -- both requirements for being matter -- even though they are invisible. A blown-up balloon demonstrates this: it has more mass than a flat balloon and clearly takes up space. Hands-on demonstrations make this invisible concept concrete.

Common Misconception

Sand is a liquid because it flows and takes the shape of its container.

What to Teach Instead

Sand appears to flow, but each individual grain is a solid with a definite shape. The bulk behavior of sand is an emergent property of many small solids moving together. This is a productive misconception to discuss because it forces students to clarify what shape and volume mean for individual particles versus bulk materials.

Active Learning Ideas

Investigation Station: Matter Sorting

Set up trays with a range of materials (rock, sand, water, honey, a balloon, foam, gel). Students handle each sample and record which state of matter it represents and the specific properties they observe, then the class discusses the tricky cases together.

30 min·Small Groups

Think-Pair-Share: What Makes a Solid a Solid?

After the sorting activity, pose this question: 'Sand pours like a liquid -- is it a liquid?' Partners discuss and must state a rule that explains why sand is still a solid. Groups share their rules and the class refines a class definition together.

20 min·Pairs

Gallery Walk: States of Matter in Daily Life

Post photos of matter in different states from everyday US contexts (steam from a coffee cup, ice on a winter sidewalk, gasoline in a fuel tank). Students identify the state and list at least two properties that make it identifiable, then compare across stations.

25 min·Small Groups

Whole-Class Modeling: Particle Arrangement Simulation

Students physically model the three states of matter: packed tightly together with locked arms (solid), loosely grouped and moving (liquid), and spread across the room with free movement (gas). The class discusses what happens when energy is added or removed.

15 min·Whole Class

Real-World Connections

• Bakers use their understanding of solids (flour, sugar) and liquids (water, oil) to create consistent recipes. They know how to mix ingredients to achieve the desired texture, like a solid cookie dough or a liquid batter.
• Firefighters need to understand the properties of gases, like steam and smoke, to navigate burning buildings safely. They know that gases expand to fill spaces and can carry heat rapidly.
• Manufacturers of canned goods, like soup or beans, rely on the definite volume of liquids to fill cans consistently. This ensures each can contains the same amount of product.

Assessment Ideas

Exit Ticket

Provide students with three small containers, each holding a different substance (e.g., a rock, water, air in a sealed bag). Ask students to write one sentence describing the shape and volume of each substance, classifying it as a solid, liquid, or gas.

Quick Check

Show students pictures of various objects and substances (e.g., ice cube, milk, helium balloon, table, steam). Ask them to hold up one finger for solid, two fingers for liquid, and three fingers for gas. Discuss any disagreements, asking students to justify their choices based on properties.

Discussion Prompt

Present students with a scenario: 'Imagine you have a block of ice, a cup of water, and a balloon filled with air. If you put each one into a much larger, empty box, what would happen to the shape and volume of the ice, water, and air? Explain your reasoning for each.'

Frequently Asked Questions

What are the three states of matter for 4th grade science?

The three states of matter are solid, liquid, and gas. Solids have a definite shape and volume. Liquids have a definite volume but take the shape of their container. Gases have no fixed shape or volume -- they expand to fill any container completely. Water is a great example because students can observe it in all three states.

How do you describe the properties of solids, liquids, and gases?

Solids keep their shape without a container, feel firm or structured, and have a definite volume. Liquids flow, take the shape of any container they are poured into, but their volume stays the same. Gases spread out to fill any space, are usually invisible, and can be compressed into a smaller volume unlike liquids and most solids.

Why is sand considered a solid even though it pours?

Each individual grain of sand is a solid -- it holds its own shape and does not change form. When you pour sand, you are moving many tiny solid grains at once, which looks like a flowing liquid. But if you look at one grain, it holds its shape no matter what container it is placed in, which is the defining feature of a solid.

How does active learning help students understand states of matter?

States of matter concepts become precise through hands-on investigation and discussion, not just reading definitions. When students sort unusual materials -- honey, foam, gel, sand -- they encounter cases that challenge simple rules, forcing them to refine their understanding. Physical simulations of particle movement also make the abstract idea of particle arrangement memorable and accurate.