The Particle Dance

Why it matters

Ice, water and steam are the SAME molecules — H₂O every time. The only difference is how the crowd behaves: standing in rows, milling about, or sprinting everywhere.

The idea in plain words

The kinetic model in one line per state. Tap them.

solid → liquid → gas

Why can you compress a gas easily but not a liquid?

Squeezing a gas closes empty space; a liquid has none to give

• state 1: solid — molecules packed in a fixed pattern, only vibrating — definite shape AND volume
• state 2: liquid — molecules slide over each other — definite volume, borrowed shape
• state 3: gas — molecules far apart and fast — no fixed shape or volume, fills everything
• Gas molecules have huge empty gaps between them
• Liquid molecules are already touching

Predict first

What changes when ice melts into water?

Same H₂O throughout. Heat loosens the grip between molecules: fixed lattice → sliding crowd → free flyers.

• the ARRANGEMENT and freedom of the molecules — not the molecules themselves — correct
• the molecules themselves change into water molecules
• the molecules disappear and reform

What you do

Heat the particle box through all three states — watch the same dots change their dance.

Check yourself

A liquid has a definite…

Pour 100 mL into any glass: the shape changes, the 100 mL doesn't.

In which state do molecules have the MOST kinetic energy?

Heat is molecular motion: the gas got the most heat, its molecules run fastest.

Solids keep their shape because their molecules…

Even in ice the molecules jiggle — they just can't leave their posts.

• volume but not shape — correct
• shape but not volume
• neither
• gas — correct
• solid
• all equal
• are locked in fixed positions by strong forces, only vibrating — correct
• do not move at all
• are heavier than in liquids