Around us are many materials like wood, metal, plastic, glass, and rubber.
Each one differs in hardness, transparency, whether it sticks to a magnet, and whether it floats.
That is why windows use clear glass and tires use springy rubber.
Pick a material to compare its properties, and drop it in water: it floats or it sinks.
Explore Various Materials
Things around you can look alike and still feel different when you touch them, let light through, meet a magnet, or sit in water. If you do not line those traits up, you pick a window material and an eraser material by the same rule. Putting hardness, how clear it is, magnet response, and floating in one place is there so you see what differs before you pick a use. Guessing all four from one name makes a clear piece and a piece that does not stick look like the same stuff.
seegongsik.com
Comparing material properties — hardness, transparency, magnetism, buoyancy
A button along the top picks wood, metal, plastic, glass, or rubber. On the left a square takes that color, and a clearer pick like glass lets more of the square show through. On the right, hardness and clarity show as how far a bar is filled, while magnet response and floating show as O or X. The lower picture puts the same pick in a water tank as a circle: a floating one sits near the water line, a sinking one sits below it, and the words for floating or sinking sit at the top. The bars and the circle do not travel through the water; only the lengths and the seat change when the pick changes.
🔍 Materials Are All Different
①Wood is light and floats
②Metal is hard. Only some metals, like iron, nickel, and cobalt, stick to magnets
③Glass is transparent — light passes through
④Rubber stretches well
⑤Each material has unique properties
Float or Sink?
It is easy to decide that anything clear must be glass. Plastic can let some light through too, so clarity alone does not lock in a material name. Floating does not make something wood, and failing to stick to a magnet does not prove it is not a metal. Naming from just one bar or one O or X on the right leaves you out of step with the other three marks. Reading hardness and whether it sits on water, then attaching a name, is late enough to keep those mixes apart.
seegongsik.com
Which materials float and which sink in water
💡 Why Float or Sink?
①At the same volume, materials lighter than water float
②At the same volume, heavier materials sink
③Wood, plastic, rubber usually float
④Metal and glass usually sink
⑤The material you pick in step 1 also changes this picture
Summary
Classifying Materials
Material → unique properties (hardness, transparency, magnetism, weight)
Every material has its own properties
Floating Condition
Compared at the same volume, lighter than water → floats / heavier → sinks
Density — weight for the same volume — decides float or sink
🎯 Key Points
①Materials differ in color, shape, hardness, transparency
②Only iron, nickel, and cobalt stick to magnets. Not every metal does. The list is on Magnets and Magnetic Force
③Some float, some sink
④Knowing properties helps choose uses
⑤Same shape, different material = different properties
Examples and Unit Test
Example 1
Among wood, metal, and plastic, which material sticks to a magnet?
1
Each material differs in whether it sticks to a magnet.
2
Metals like iron, nickel, and cobalt stick to a magnet, but wood and plastic do not.
▸ Metal
Iron, nickel, and cobalt stick to a magnet; wood and plastic do not.
Example 2
What happens to a piece of wood and a piece of metal when you put them in water?
1
Each material differs in whether it floats on water.
2
Wood is light and floats, while metal is heavy and sinks.
▸ Wood = floats / metal = sinks
Depending on its properties, a material may float or sink in water.
Unit-test style
Which statement about the properties of materials is correct?
①Every material floats on water
②Metal is hard, and some kinds stick to a magnet
③Light cannot pass through glass
④Wood sticks well to a magnet
⑤All materials have the same properties
▸ ② Metal is hard, and some kinds stick to a magnet
1
Metal is hard, and some metals like iron, nickel, and cobalt stick to a magnet.
2
Metal is heavy and sinks in water (①), glass is clear so light passes through (③), wood does not stick to a magnet (④), and each material has its own different properties (⑤).