In a solid the particles are close and held in fixed positions. They vibrate but cannot move past each other.
Step 1: Something to Notice
Watch first. The explanation comes later.
Ice, water and steam are the same substance. One is rigid, one pours, one fills any container it is put in.
If the particles are identical, where do such different properties come from?
Step 2: Find Out
Melt something and check whether the particles changed.
Step 1 — Predict
When ice melts, what happens to the particles themselves?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
Liquid
Still close together, but free to slide past each other. That is why a liquid pours and keeps its volume.
Gas
Far apart and moving fast in all directions. A gas fills its container and can be squashed.
The particles never change
Only the arrangement and the motion. Ice, water and steam are the same particles throughout.
Same particles, different arrangements
In a solid the particles are close and fixed in place, in a liquid close but mobile, in a gas far apart and fast. The particles themselves are identical in all three.
The properties follow from the arrangement
Solids hold their shape because the particles cannot move past each other. Gases fill their container because nothing holds them together. Each everyday property traces to the arrangement.
Step 4: A Common Mistake
Lots of people think
“The particles themselves change when a substance melts — they get softer or smaller.”
Step 5: Why Ice Floats
The same idea somewhere new.
Almost every substance is denser as a solid than as a liquid. Water is the strange exception: its particles lock into a pattern with gaps in it, so ice is less dense than water and floats. If it behaved normally, ponds would freeze from the bottom up and almost nothing in them would survive a winter.
Step 6: Think It Through
Practice makes it stick.
Pouring
Problem 1 of 2
Why can a liquid be poured but a solid cannot?
Melting Ice
Problem 2 of 2
When ice melts, what happens to the particles themselves?
Three Arrangements
1 of 4
Match each state to its arrangement.
Tap a card on the left to start.
2 of 4
Which state can be squashed noticeably?
3 of 4
Do particles change when a substance melts?
4 of 4
Why does ice float on water?
Step 7: Quick Check
Show what you know.
Question 1 of 1
Where do the different properties of ice, water and steam come from?
Step 8: Explain It in Writing
Claim, evidence, then reasoning.
The question
Ice, water and steam are the same substance with very different properties. Explain.
Words to usearrangementfixedslidingfar apartidenticalheldmove
Fill in all three boxes. The reasoning box is the one that matters most.
What You Found Out
- Solid: close, fixed in place, vibrating — keeps its shape.
- Liquid: close but sliding — pours, keeps its volume.
- Gas: far apart, fast — fills its container and can be squashed.
- The particles are identical in all three; only the arrangement changes.