Lesson 2: Solids, Liquids, and Gases
Solids, liquids, and gases behave differently when their shape or container changes. Familiar materials, including pourable grains, help explain how shape and volume can be used to tell these states apart.
Key Ideas
- Solid, liquid, and gas are three common states of matter.
- A solid keeps its own shape. A liquid flows and takes its container’s shape. A gas spreads out to fill its container.
- Some solids, such as sand, can be poured. Each grain still keeps its own shape.
- A material’s state can change. Ice, liquid water, and water vapor are all water.
Vocabulary
- Matter: Anything that has mass and takes up space.
- Solid: Matter that keeps its own shape and takes up a set amount of space. Solids can be hard or soft.
- Liquid: Matter that flows and takes its container’s shape, while keeping the same amount of space.
- Gas: Matter that spreads out to fill its container.
Discussion Questions
- If you discovered a brand new substance no one had ever seen, how would you figure out what state of matter it is?
- Why are solid, liquid, and gas useful categories for everyday materials? What could you investigate about other states of matter?
- Sand pours like a liquid but piles up like a solid. What does this tell us about the limits of our categories?
Hands-On Activity: Making Oobleck
Supply List
- 1 cup of cornstarch per student or pair
- Half a cup of water
- A bowl or tray
- Food coloring (optional)
- Newspaper or a plastic tablecloth to protect surfaces
- Notebook and pencil
Instructions
- Mix the cornstarch and water together in the bowl. Add a drop of food coloring if desired. Stir slowly until combined.
- Try hitting the surface of the oobleck quickly with your fist. What happens?
- Now rest your hand on the surface and let it sink in slowly. What happens this time?
- Try rolling some in your palms into a ball. Hold it still and watch what happens.
- Pour it slowly from one hand to the other. What does it look like when it flows?
- Discuss: is oobleck a solid or a liquid? What evidence do you have for each answer? Does it fit neatly into one category, or does it challenge the definitions you built?