Question

How are solids , liquids , and gases similar ? How are solids , liquids , and gases similar ? @Chemistry

Answer 1

They're all made of atoms. That is, they're all made of matter. We can distinguish them from, say, electromagnetic radiation, which is not made of atoms.

Furthemore, if you mean the solid, liquid and gas phase of the same substance, then they're related in that they're all made of the exact same type of atom, or type of molecule. Solid CO2 is made of molecules constructed of one carbon atom bonded to two oxygen atoms. So is liquid CO2, and so is gaseous CO2. Nothing about the molecules changes when you go from one phase to another. It's only the arrangement of the molecules that changes, how they are distributed in space, and how they move.

This may seem obvious to you, with your 21st century knowledge, but at one time, before we had the atomic theory of matter, it was not obvious at all. After all, the properties of substances change quite a bit when they melt or boil. Why should we assume they remain the same substance at all? In fact, it was originally thought they did not. When water boiled, the assumption was that it changed into an entirely different substance, steam or even just air, and that this had a lot in common with, for example, a chemical change like alcohol *burning*, when it changes into CO2 and water vapor.

So the fact that we can now distinguish a purely physical change, like water turning into steam, and a chemical change, like alcohol burning into CO2 and water vapor, is an important insight of atomic theory.