@Box-Poorsoft (View Post)
Energy and matter are separate entities.
> But when energy can't be destroyed, does that mean to break something, you can fix that?
Energy can't be touched, it can be converted to matter (in very very extreme cases!) but it isn't matter.
By conversation of energy it means that in the vacuum, with an initial push and no other forces acting upon you, you will slide on indefinitely.
In real life, there are forces like gravity, drag, resistance, friction and many others.
Drag and air resistance may be described as hitting tons of really really small air balls. When you throw a tennis ball, it glides through all those little air balls while pushing them out of the way. Every single push takes energy (Energy can be transferred, but not created or destroyed!) and after a while the ball slows down in midair.
Gravity is just like two magnets pulling on each other, I can't think of a way to describe it to you easily.
In nuclear fusion reactors, the initial push must be done with external effects, using up a tremendous amount of energy. After that, the tipping point is reached and hydrogen begins to bond with other hydrogen, creating helium. Creating those bonds gives off a lot of energy and it pretty much becomes a chain reaction. Some of the energy might be used to heat water and create power. Going even further, you could even convert energy to matter and vice versa, that's what happened during the Big Bang.

To freeze water you remove some of its internal energy by moving it somewhere else, with some external object that has less energy than the water. Energy travels where there is the least of it, so to equalize. After freezing the water, the two objects (The system) are now in balance.
If you're more interested, read up on thermodynamics.