The Chemical Detective
Read the clues and crack the case: is it a solid, liquid or gas? Master the particle model and the changes of state like a true detective.
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The Chemical Detective 🔍
Every substance leaves **clues**: does it keep its shape? Does it fill its container? From the clues a good chemist can name the **state of matter**. Crack the cases by mastering the **particle model** and the **changes of state**.
Three states, three arrangements 🗂️
The particle model explains each state:
Match each state to its particle arrangement
- Solid
- Liquid
- Gas
- A regular pattern, vibrating in fixed positions
- Close together but random, able to flow
- Far apart, moving quickly in all directions
Read the clues
A substance has a fixed volume but takes the shape of whatever container it is poured into. Which state is it?
- A liquid
- A solid
- A gas
- None of these
Changing state 🔄
Add or remove energy and a substance changes state: - **Melting**: solid to liquid. - **Freezing**: liquid to solid. - **Boiling** (or evaporating): liquid to gas. - **Condensing**: gas to liquid. - **Sublimation**: solid straight to gas.
Match each change to what happens
- Melting
- Freezing
- Condensing
- Sublimation
- Solid to liquid
- Liquid to solid
- Gas to liquid
- Solid straight to gas
Heat it up
An interactive activity.
Name the change
Steam touches a cold window and turns into droplets of water. Which change of state is this?
- Condensing
- Melting
- Freezing
- Boiling
The flat part of the curve 💡
Heating gives particles more energy. But during **melting or boiling** the temperature **stays constant**: the energy goes into **breaking the forces between particles**, not into raising the temperature. That is why a heating curve has a **flat part** at each change of state.
Particle model
Select the TWO true statements about the particle model.
- In a solid, particles vibrate in fixed positions
- In a gas, particles are far apart and move quickly
- In a liquid, particles are locked in a regular pattern
- Gas particles do not move at all
A key number
An interactive activity.
Crack the case
An interactive activity.
States-of-matter frame
Solids keep a fixed shape; liquids take the shape of their _____; gases fill all the space. Heating a solid makes it _____ into a liquid, then _____ into a gas. During a change of state the temperature stays _____.