Learners will reason their way to the discovery that all matter is made of particles too small to see. They also work out the difference between a single substance and many materials assembled together.

Key Ideas

• All matter is made of particles too small to see, even with most microscopes. A single grain of sugar contains millions of individual particles.
• A larger amount of something does not mean larger particles. It means more particles. The particles of a substance are all the same size. That is part of what makes it that substance.
• Those particles are what give a substance its properties. When you tear paper into smaller and smaller pieces, each piece is still paper, because the fundamental particles have not changed.
• A single substance can be put back together. Water can be evaporated and collected again and it is still water. But many materials assembled in a specific way cannot always be restored. A bicycle taken apart is no longer a bicycle, even though the metal, rubber, and plastic particles are all still there.

Vocabulary

• Particle: A tiny piece of a material. All matter is made of particles too small to see individually.
• Particulate nature: The idea that all matter is made of fundamental particles.

Discussion Questions

• If particles are too small to see even with most microscopes, how do scientists know they actually exist?
• A smell travels across a room even though the object producing it is not moving. What does this tell us about the particles of that substance?
• When you dissolve sugar in water you can still taste it. What other senses might help us detect particles we cannot see?