Lesson ​2
Solids, Liquids, and Gases Introduction
Everything around us exists as a solid, liquid, or gas. Learners sort familiar objects and materials into one of these three states of matter, work out the defining features of each, and begin building their own definitions.

Key Ideas
  • Every material falls into one of three states based on how it acts: solid, liquid, or gas.
  • A solid keeps its own shape without any help from a container. A liquid has no fixed shape of its own and adjusts to whatever holds it. A gas has no fixed shape or volume and spreads to fill whatever space is available.
  • Some solids, like sand or sugar, can be poured because their tiny pieces are loose. But each individual grain is still a solid. Pour them into a pile and they hold that shape. A liquid cannot do that.

Vocabulary

  • Matter: Anything that takes up space and has weight.
  • State of matter: One of the three forms that matter can take: solid, liquid, or gas.
  • Solid: A state of matter that holds its own shape regardless of its container.
  • Liquid: A state of matter that flows and takes the shape of whatever container holds it.
  • Gas: A state of matter that spreads out to fill any space it is given.

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 do you think scientists settled on three states of matter instead of more or fewer?
  • Sand pours like a liquid but piles up like a solid. What does this tell us about the limits of our categories?

Supplies:
Hands-On Activity: Making Oobleck
 SciShow Video Here and Crash Course Kids Here

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?

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L2 Solids, Liquids, and Gases UPDATED by Selene
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