Can you imagine something so tiny that you can't even see it? Well, everything around you right now, everything you can touch and even the air, is made of little itsy bitsy building blocks, so small that they can't be seen without a super powerful microscope.
These building blocks are called molecules. They are made of super small pieces of elements, like gold, iron, hydrogen, and oxygen, combined in groups of two or more!
When two pieces of hydrogen combine with one piece of oxygen we get a special molecule, one that you probably are familiar with, called water. All water everywhere is made of tiny water molecules.
Even oxygen gas in the air is made of molecules, which in this case, are two pieces of oxygen joined together. A single piece of oxygen doesn't really exist by itself in nature. The single pieces become parts of molecules, like water and oxygen gas.
(by Mya Kagan)
Slowing Down Molecules
Molecules move! In liquid water, molecules move right past each other. That's why water can flow! But if you want to slow down water molecules, there's a pretty easy way: freeze them!
Once molecules slow to a point where they've pretty much stopped moving, you get a solid material, like ice.
Try slowing down some water molecules in an ice cube tray. You can even use the molecules that make up juice if you want to make a tasty frozen treat!
The tasty liquid juice will become a tasty solid juice because you affected its molecules, slowing them down!