States of matter simulation

What the simulation shows

Everything around us is made of particles far too small to see. How those particles are arranged and how they move decides whether a substance is a solid, a liquid or a gas. This simulation draws the same set of particles in a box. Press Heat and they move from solid to liquid to gas. Press Cool and they go back the other way.

• Solid: particles packed in neat rows, vibrating in place. That is why a solid keeps its shape.
• Liquid: particles still touching but jumbled, sliding past each other. That is why a liquid flows and takes the shape of its container.
• Gas: particles far apart, moving fast in all directions. That is why a gas spreads out to fill whatever space it is in.

Why a particle model helps

Children can see ice melt, but they cannot see why. Without a model, "melting" is just a word for something that happens. A particle picture gives a reason: heating gives the particles more energy, so they move more, until they break out of their fixed places. Cooling does the reverse.

It also clears up common misconceptions. Many children think the particles themselves melt or expand, or that a gas weighs nothing. In the simulation the particles stay the same size and the same number throughout. Only their arrangement and movement change.

Where this fits in school

• US, grade 5: the Next Generation Science Standards ask students to develop a model showing that matter is made of particles too small to be seen (5-PS1-1).
• US, middle school: NGSS MS-PS1-4 asks students to model how particle motion, temperature and state change when thermal energy is added or removed. The simulation is a simple starting model for that.
• England, Year 4: pupils group materials as solids, liquids or gases and observe that some materials change state when heated or cooled.
• Younger children: use it to sort everyday things into solids, liquids and gases, and to talk about what "heating" and "cooling" do.

A 10-minute states of matter activity

• Start with the solid. Ask the child to describe the particles using three words.
• Heat once. Ask: "What is this change called?" (melting). Ask for a real example, such as chocolate in a warm hand.
• Heat again. Name the change (boiling or evaporating) and ask where they have seen it, such as steam from a kettle or a puddle drying up.
• Cool back down to a liquid. Name the change (condensing) and link it to water droplets on a cold glass.
• Cool to a solid. Name the change (freezing) and ask what has to happen to the particles for it to happen.

Back up the screen with something real. An ice cube on a plate, watched over ten minutes, makes a perfect partner to the simulation, and needs no special equipment.

Words worth knowing

Melting is solid to liquid. Freezing is liquid to solid. Evaporating and boiling are liquid to gas: evaporating happens at the surface at any temperature, while boiling happens throughout the liquid at its boiling point. Condensing is gas to liquid. Older students may also meet sublimation, where a solid turns straight into a gas, as dry ice does.

Learning more

Science is part of Eurekami's skill map, with lessons that draw science diagrams live and narrate them in English or Spanish. For older students, Exam Prep includes GCSE Combined Science practice papers.