What is "empty space"?
I always hear this term: "empty space." It is synonymous with "vacuum," but I am having trouble understanding either of these two ideas.
How can space be "empty?"
Homework Statement
Why does water volume increase when heated past 4 degrees Celsius?
2. The attempt at a solution
I know that water molecules move quicker when energy is applied (e.g. heat), but I don't understand why the volume of water must increase. Why can't water molecules just move...