seegongsik
Grade 3 (age 8-9)

grade 3 Properties of Liquids and Solids

An eraser keeps its shape whether it sits in a pencil case or on your palm, but milk poured from a cup onto a plate spreads out flat in the shape of the plate. A material whose shape and volume stay fixed is a solid, and a material whose volume stays the same while its shape follows the container is a liquid. The difference comes from how tightly the tiny bits (particles) that make up the material hold on to each other. The first picture compares the particles of a solid, a liquid, and a gas, and the second pours 200 mL of water into three containers to show that only the shape changes.

Three states of matter

🔬 The three states as particles
①Solid: particles hold on tightly and only jiggle in place, so the lump keeps its own shape
②Liquid: particles stay close but slide past one another, so they spread along the bottom of the container
③Gas: particles are far apart and fly around fast, so they fill the whole container
④The same water becomes ice, a solid, when it freezes and steam, a gas, when it boils

A liquid takes the shape of its container

💧 What a liquid does
①Change the container and the shape changes to match it
②The amount (volume) stays the same, so all three containers in the picture hold 200 mL
③In a narrow cup the water rises high, and in a wide bowl it spreads out low
④Even if you tilt the container, the surface stays level

A solid keeps its own shape anywhere

🧊 What a solid does
①A wooden block keeps the same shape and size on the floor, in a bowl, or in a cup
②You can pick it up, and pressing on it does not easily change its shape
③Its shape and volume are fixed, so you can stack it neatly
④Sand and salt pour into the shape of a container, yet each grain keeps its own shape, so they are solids

Summary

Solid
Solid = Fixed shape + Fixed volume
Particles are packed tight and jiggle in place
Liquid
Liquid = Changing shape + Fixed volume
Particles stay close and slide past each other
Gas
Gas = Changing shape + Changing volume
Particles are far apart and spread through the whole container
🎯 Key points
①A solid has a fixed shape and a fixed volume
②A liquid's shape follows the container, but its volume stays fixed
③A gas takes both the shape and the volume of its container
④The three states differ in how tightly their particles hold together
⑤Water is a material you can see in all three states: ice (solid), water (liquid), and steam (gas)

Examples and Unit Test

Example 1
If you pour 200 mL of water from a wide bowl into a narrow cup, what happens to its shape and its amount?
1
A liquid changes shape to match its container, so in the narrow cup the water rises higher.
2
If none is spilled, the amount (volume) does not change, so it is still 200 mL.
▸ The shape becomes the cup's shape, and the amount stays 200 mL
The water looks taller only because the cup is narrower; the amount is the same.
Example 2
If you move a wooden block and some water from container to container, what happens to the shape of each?
1
The wooden block is a solid, so its shape and volume stay the same in any container.
2
Water is a liquid, so its volume stays the same while its shape follows the container.
▸ The block keeps its shape / the water takes the container's shape
Checking whether the shape follows the container tells a solid from a liquid.
Unit-test style
Which statement about the properties of solids and liquids is correct?
①When a liquid changes container, its amount (volume) changes too
②A solid keeps its shape even when it changes container
③A liquid has the same shape whatever it is poured into
④A solid changes shape to match its container
⑤Tilting the container makes the water surface slant
▸ ② A solid keeps its shape even when it changes container
1
A solid has a fixed shape and volume, so its shape stays the same in any container.
2
A liquid keeps its volume in a new container (①) and its shape follows the container (③). It is the liquid, not the solid, that takes the container's shape (④), and the surface stays level even when the container is tilted (⑤).
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Properties of Materials
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Magnets and Magnetic Force

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