Question: why does smoke and steam curl in the air? why not go straight up? and where does the smoke/steam go when we cant see it anymore? (i hope that made sense...)

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  1. The particles that make up air are constantly moving and they are never still. When steam and smoke are introduced into the air, you can see this with the curling patterns that occur as the steam and smoke particles are pushed by air particles moving into them.

    Where smoke and steam end up after going invisible are two very different places because of what they are made up of. Smoke is made up of very small solid particles and these can be carried away by wind currents into the atmosphere or fall to the ground over time.

    Steam on the other hand is made of small water droplets. If the steam condenses on a surface, you get water but if you let the steam escape, the water droplets become smaller as they move into the atmosphere. They don’t disappear, the water droplets become too small to be seen by the eye.

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  2. Yes, smoke “dissipates” – so the particles separate and go their separate ways. Steam water droplets evaporate and get too small to see. There’s water in the air already, we just don’t see it because it’s gaseous water – too small.

    Why smoke and steam curl is a super-cool question. I NEVER get tired of watching that. If you burn a candle that generates a bit of smoke there’s that ultra-smooth bit of smoke that goes right up and then at some point you get this chaos start where things go nuts, and it seems to be a very definite point.

    The point depends on a lot of things. What you’re looking at are a combination of things all in play. So the straight smooth bit is usually the hot part of the smoke. Things rise straight up because they’re being carried by heat and therefore the movement of the particles are quick and even.

    As they move up they cool. They also encounter regular air molecules that aren’t part of the smoke trail. At first the smoke particles don’t care. They barge right through those air molecules and keep going straight. But as the particles slow down (because they’re colliding with things) there will come a point where they slow down and start mixing with regular air, and new currents start developing, in the way that you see when you mix something in water – you get new little currents going off randomly.

    Though it looks like chaos, it’s governed by very simple physical laws.

    Yet it’s still complex and impossible to predict because it’s so complex. So what exactly happens depends on very small air flow changes in the room, and lots of other things like how fast the candle is burning and the temperature of the rest of the air.

    This area of science – simple things operating by simple laws, but still being unpredictable, is called chaos theory. There’s a really great book called Chaos by James Gleick that you could read. It talks about smoke and water patterns. If you want to study this area, do maths!

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  3. The air currents make the the smoke and steam curl. This question is related to something called chaos theory, in which tiny changes lead to big effects. When you roll ball down a hill its path is different each time. Same with water drops sliding down a window pane. The same slight differences means that the smoke and steam do not go straight up but have slight deviations which we see as curling. Jame Gleick has a interesting book about this.

    We see “steam” because the cooler air causes small water droplets to form. If these droplets evaporate, then they become invisible. Smoke is slightly different because there are small ash and soot particles that remain as solids and cannot evaporate. However, wind might spread out these ash and soot particles so that we do not see them anymore.

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