What is an atom?
An atom is a tiny building block that all stuff is made of. Air, water, your toys and even you are built from atoms, far too small to see.
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Atoms & matter
What everything is made of — atoms, solids, liquids and gases.
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What it is and why it matters — intuition first, little or no math.
Why does water boil at different temperatures?
The boiling point is the temperature at which a liquid bubbles into a gas, and it depends on how hard the air presses on the liquid. High on a mountain, water boils below 100 °C; in a pressure cooker, it boils above 100 °C.
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What is an electron?
An electron is a tiny particle with a minus charge that moves around the middle of every atom. When lots of electrons move along a wire together, electricity flows.
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What are evaporation and condensation?
Evaporation is a liquid slowly turning into a gas, and it soaks up heat — that is why wet skin feels cold. Condensation is the opposite, a gas turning back into a liquid, and it gives that heat back.
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What is pressure?
Pressure is how hard something pushes on each bit of a surface. The air around us presses on everything, and squeezing a gas into a smaller space raises its pressure — and warms it up.
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