Lesson 13: Particles and States of Matter
Particle models help explain the different shapes and volumes of solids, liquids, and gases. Changes in particle motion, spacing, and arrangement connect heating and cooling with changes of state.
Key Ideas
- Matter is made of tiny particles. How they move and fit together helps explain solids, liquids, and gases.
- In a solid, particles jiggle in place. In a liquid, they move past one another. In a gas, they move freely and spread out.
- Melting or freezing changes how particles are arranged. If none of the material escapes, its mass stays the same.
- A whole object can move while its tiny particles are also moving. Water flowing down a stream shows both kinds of movement.
Vocabulary
- Solid: Matter that keeps its own shape and takes up a set amount of space. Its particles jiggle in place.
- Liquid: Matter that flows and takes the shape of its container. Its particles stay close but move past one another.
- Gas: Matter that spreads out to fill its container. Its particles are far apart and move freely.
- Mass Movement: A whole object or amount of material moving from one place to another, like flowing water.
Discussion Questions
- A closed sample keeps the same mass during a change of state. Why might water need more room when it freezes?
- How does cooling change particle motion? Why should we also consider particle interactions and arrangement when predicting a substance's state?
- A smell spreads faster in a warm room than a cold one. How does the particle model explain this?
Hands-On Activity: Diffusion Experiment
Watch: https://www.youtube.com/watch?v=OVnnz7RB6bk
Supply List
- Three identical clear glasses or jars
- Hot water (caregiver pours; not boiling)
- Cold water (add ice first, then remove ice before adding food coloring)
- Room temperature water
- Food coloring (one color)
- A dropper or spoon
Instructions
- Fill each glass with one type of water: one hot, one room temperature, one cold. Label them.
- At the same time, add one drop of food coloring to each glass. Do not stir.
- Observe all three glasses and record what you see every 30 seconds for about three minutes.
- Discuss: in which glass did the color spread fastest? In which did it spread slowest? Why?
- Connect to particles: warmer water generally has faster thermal motion. Color spreading can also involve bulk currents, so this demonstration does not isolate diffusion alone. Record what actually happens in each glass.
- Write your conclusion: what did you observe about mixing at different temperatures? Which observations might reflect diffusion, and which might involve bulk movement?