Steam is formed at 100°C but I see “steam” being produced at less than that temperature. What is that and why isn’t it steam?
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There’s some good answers here already, but they’re a bit past ELI5 explanations, so I’ll try and keep this to that level. Steam is created when water molecules have enough energy to escape their liquid form. Some molecules have more energy than others and can escape well before the entire liquid mass is “boiling”. Lot’s of things can effect this, such as adding salt to water or lowering air pressure as it’s air pressure that keeps the molecules trapped in the liquid.
This can be shown using a syringe. Suck some warm, but not boiling, water into a syringe, cover the end and pull the plunger outward. The water will start boiling as there is less pressure keeping those molecules in the water, thus making it easier for them to escape. So you can actually make water boil without ever being near 100°C.
What’s really interesting is that when water boils, it actually cools down. The temperature of water is the amount of energy (heat) within the water. As these energetic molecules escape, they take that energy with them, leaving the liquid water cooler. It’s why a boiling pot doesn’t instantly evaporate.
So liquid water doesn’t need to be 100°C to create steam, only individual molecules need enough energy to escape the liquid mass to create steam. We only say 100°C is boiling point, because that is when you will see liquid water “boil” at sea level.
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