Same stuff, three outfits.

It all comes down to packing and jiggling.

Everything around you is made of particles — tiny building blocks far too small to see, even with a classroom microscope. And every single particle is always jiggling. That jiggle is what "having heat" really means. So the difference between the three states isn't which particles you have — it's how tightly they are held together and how fast they are moving.

That neat, repeating pattern in a solid has a name — a lattice, which just means a tidy grid that repeats over and over, like the squares on graph paper. Here's the same three states laid out side by side so you can compare them in one glance:

Notice the bottom rows of the table. A solid keeps its own shape; a liquid borrows its container's shape but keeps the same amount (pour 200 mL of juice into any cup and it's still 200 mL); and a gas gives up on shape and on staying put, swelling to fill whatever space it's trapped in. Shape first, then space — that's the ladder you climb as things heat up, and the ladder you climb back down as they cool.

Drag the heat — watch them freeze, melt, and boil.

Each dot is one particle, and the thermometer on the right shows the temperature in degrees Celsius (°C). Slide the heat up and watch the neat solid lattice loosen into a flowing liquid as you pass 0°C, then burst apart into a gas that fills the box once you pass 100°C. Slide it back down to freeze everything again. There's no wrong way to play — drag it fast, drag it slow, and watch what changes.

Notice three things while you play. First, the particles never disappear and no new ones pop in — there are always the same number, no matter the temperature. Second, they don't get bigger or smaller; they just spread out or crowd together. Third, the change isn't instant — right around 0°C the grid goes wobbly before it fully melts, and right around 100°C the liquid starts flinging particles loose before the whole box turns to gas. That's the costume change happening in front of you.

A few things worth trying with your own hands: park the slider exactly on 0°C and watch the box hover between locked and loose — that's the melting point caught in the act. Then ease it up to just under 100°C, where the liquid is restless but still pooled, before nudging it over into a full gas. Finally, drag it all the way to the top and then slam it back to the bottom: the gas crowds back into a liquid and re-freezes into a grid, the whole journey in reverse. The colour shifts too — cool blue-green when slow, warm orange when fast — a stand-in for the energy the particles are carrying.

Every switch has its own name.

When a material jumps from one state to another, scientists call it a change of state. There are six of them, and they come in pairs: a heating one that goes "forward," and a cooling one that goes back the other way. Click any arrow in the diagram to see what it's called, whether it needs heating or cooling, and a real example you've seen.

You probably already know the two most famous ones by heart — melting and freezing — but the diagram lays all six out together so the pattern jumps straight out at you. Take your time and tap through every arrow; reading the little example attached to each is the quickest way to make the names stick, because every single change of state here is something you have watched happen with your own eyes.

A quick word about the top-right arrow. Boiling and evaporating are both liquid turning to gas — the difference is just speed and where it happens. Evaporation is slow and happens only at the surface (a puddle drying over a whole afternoon). Boiling is fast and happens all through the liquid at once, which is why a pot rolls with bubbles. Same change of state, two settings on the same dial.

Spot the pattern across the whole diagram and you'll never have to memorise the six names as a random list. The two arrows along the top both point "uphill" from tightly packed to free, and both need heating. The two along the bottom point "downhill" from free to packed, and both need cooling. The big curves are the same idea, taking the express route past the liquid middle. So whenever you meet one of these words in class, just ask: is this thing getting looser (heating) or tighter (cooling)? That single question places it on the map instantly.

Water freezes at 0, boils at 100.

Every material switches states at its own special temperatures. The temperature where a solid turns to liquid is its melting point; the temperature where a liquid turns to gas is its boiling point. Water has wonderfully tidy ones, which is exactly why we built the Celsius scale around it.

Here's a neat detail: the melting point and the freezing point are the same temperature — 0°C for water. Going up through it, ice melts; coming back down through it, water freezes. It's one doorway you can walk through in either direction; which way you're heading just depends on whether heat is going in or coming out.

Now the small print on "100°C." Water only boils at exactly 100°C when the air is pushing on it with normal sea-level pressure (pressure is just how hard the surrounding air squeezes down). High up a mountain, the air is thinner and pushes less, so water particles escape more easily and water boils at a lower temperature — sometimes around 90°C on a tall peak. That's why a recipe might say "boil longer at high altitude": the water is bubbling, but it's cooler than the 100°C your noodles were expecting. The melting and boiling points are real and reliable — they just quietly depend on the pressure around them.

And it isn't only water that has these switch-over temperatures — every material has its own. Iron sits as a solid in your hand because its melting point is roughly 1,500°C; you'd need a furnace to pour it as a liquid. The oxygen you're breathing is a gas at room temperature because its boiling point is about −183°C — so to ever see liquid oxygen you'd have to chill it far colder than the coldest place on Earth. "Solid," "liquid," and "gas" aren't permanent labels glued to particular materials; they're just whichever outfit a material happens to be wearing at the temperature around it right now. Rock can run as molten lava; air can be chilled into a liquid. Same idea, different dials.

One last surprise hides inside melting. Put a thermometer in a glass of icy water and warm it gently: the temperature climbs to 0°C — and then, while the ice is actually melting, it stops climbing and parks at 0°C until the very last sliver of ice is gone. Where did the heat go? Into the hard work of prising the particles out of their locked grid, rather than into speeding them up. Only once the ice has fully melted does the temperature start rising again. The very same pause happens at 100°C while water is boiling. So every change of state quietly "soaks up" a chunk of energy without changing the temperature — a detail you'll bump into again and again the deeper you go in chemistry.

You watch this happen every single day.

Two of these changes are so common you've stopped noticing them. The first is evaporation. Leave a puddle on the pavement after rain and by afternoon it's gone. The water didn't vanish or soak away — its fastest particles kept escaping from the surface into the air as an invisible gas called water vapour. (Important: that's vapour, the invisible gas — not the white cloud you see above a kettle. We'll get to that in a second.) Evaporation doesn't even need boiling; it happens slowly at any temperature, which is how wet hair dries and how laundry stiffens on the line.

The second is condensation — evaporation run backwards. Pour an ice-cold drink and within minutes the outside of the glass is beaded with water. That water came out of the air: invisible vapour drifting past touched the cold glass, lost energy, slowed down, and clumped back into tiny liquid droplets you can see. The same thing fogs up a bathroom mirror after a hot shower and paints dew on the grass at dawn.

Here's the kettle answer you were promised. The truly invisible stuff right at the spout is steam (water vapour). The white billowing cloud just above it is that vapour already condensing back into millions of tiny liquid droplets in the cooler room air — which is why you can see it. So a "cloud of steam" is really a cloud of teeny water droplets. Clouds in the sky are the exact same trick on a giant scale.

Evaporation has a hidden superpower, too: it cools things down. When you get hot and sweat, the fastest, most energetic water particles are the ones that escape your skin first — and they carry their energy away with them, leaving the cooler, slower particles behind. That's why climbing out of a swimming pool feels chilly even on a warm day, why a wet flannel on your forehead soothes a fever, and why a panting dog stays a little cooler. Evaporation is nature's air-conditioning, running on the simple fact that the escaping particles take their heat with them.

That giant scale runs the whole planet, and it's called the water cycle. The Sun heats lakes and oceans; water evaporates into vapour and rises; high up where it's colder it condenses into droplets to make clouds; the droplets join up, get heavy, and fall as rain (or, colder still, freeze and fall as snow). Then it all starts over. It's the same water particles, just changing outfits over and over, around the whole world, forever.

Sometimes a solid skips straight to gas.

Usually you go solid → liquid → gas, climbing the ladder one rung at a time. But a few materials take the shortcut: they jump straight from solid to gas without ever being a puddle in between. That skip-the-middle move is called sublimation (and the reverse — gas straight to solid — is deposition, the frost-on-a-cold-window one from the diagram).

The classic example is dry ice, the frozen carbon dioxide that makes spooky fog at concerts and Halloween parties. Dry ice never melts into a cold puddle — it turns straight into carbon-dioxide gas, which is why it leaves no wet mess and seems to "smoke" as it disappears. (That visible fog is actually ordinary water vapour from the air condensing in the cold, riding along with the invisible carbon-dioxide gas.) You can spot sublimation in gentler places too: old snow can slowly shrink away on a freezing but sunny day without ever melting, and ice cubes left for weeks in the freezer get smaller and frostier as they slowly sublime. It's rarer than melting and boiling — but it's the same family of idea: heat gives particles enough energy to break free, even straight from a locked solid.

Sublimation even hides in your snack cupboard. Freeze-dried strawberries and the crunchy "astronaut ice cream" sold in museum gift shops are made by freezing the food solid and then letting the ice inside it sublime straight off as vapour — pulling the water out without ever turning the food into a soggy puddle. The same trick dries the little vegetables in instant noodles and the powder in instant coffee. And while solids, liquids, and gases are the three states you'll meet every single day, scientists do count a few rarer ones — like plasma, the super-hot, electrically charged state that stars and lightning are made of. For life here on the kitchen counter, though, the big three are the whole story.

Do the particles themselves melt?

This is the trip-up almost everyone makes at first, so let's name it out loud and clear it up.

A close cousin of this myth is "the gaps fill with air." Nope — when ice melts or water boils, the space between particles isn't air sneaking in. It's just empty space (or, in a gas, more of the same particles spread far apart). Keep coming back to the one rule: the particles don't change — only their spacing and their energy do.

Name the state.

Ten everyday things, one at a time. Decide whether each one is a solid, a liquid, or a gas at normal room temperature, then tap your answer. A couple of them are sneaky on purpose — read the little note after each to see why.

Two questions to lock it in.