Forces are the way that energy is transferred from one object to another when they interact, but forces are not the energy itself. Gravity is a force, so it just provides one way for objects to exchange and transform energy to different states. As a force, no energy can be extracted from gravity itself.

Work is the amount of energy necessary to move an object from one point to another. Imagine moving a table or seat from your living room to your dining room. On the other hand, power is the rate at which the energy is spent.

The major difference between force and power is that force is an action on a body or interaction of two bodies. While power is the amount of energy consumed during an action over the body.

When two objects interact, each one exerts a force on the other. These forces can transfer energy between the objects. For any such pair of objects the force on each object acts in the direction such that motion of that object in that direction would reduce the energy in the force field between the two objects.

Any object that possesses mechanical energy – whether it is in the form of potential energy or kinetic energy – is able to do work. That is, its mechanical energy enables that object to apply a force to another object in order to cause it to be displaced.

In physics, energy is a property of matter. It can be transferred between objects, and converted in form. It cannot be created or destroyed. Everything in the Universe is made up of matter and energy.

Typically for most forms of matter the phase is determined by the amount of energy possessed by the molecules of matter. If we add heat to the ice thereby increasing the energy in the molecules of water these molecules begin to vibrate at much higher velocities.

Energy is a property that matter has. The same amount matter can have different amounts of energy and so represent different states of matter. For example, if you add energy to an ice cube made of water, it becomes liquid water, and if you add even more energy, it becomes steam.

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The change from the liquid state to the solid state is called freezing. As the liquid cools, it loses thermal energy. As a result, its particles slow down and come closer together.

Again, the molecules do not go through an intermediate liquid state when going from the gas to the solid. See also physical vapor deposition, which is a class of processes used to deposit thin films of various materials onto various surfaces. Deposition releases energy and is an exothermic phase change.

Matter either loses or absorbs energy when it changes from one state to another. For example, when matter changes from a liquid to a solid, it loses energy. The opposite happens when matter changes from a solid to a liquid. For a solid to change to a liquid, matter must absorb energy from its surroundings.