Sun is the source of heat. It also provides thermal energy.

A force is required to change an object's velocity.

The most significant resource that a coal fired power station uses is of course coal. Coal is a non renewable natural resource and mining of coal has significant negative effects. In many cases coal is mined in sensitive grassland and wetland habitats - causing significant water pollution. Power stations also rely on large amounts of freshwater in the cooling towers as part of the power production process.

Natural gas is crucial for heating and cooking. It is not renuable so once humans use it up, it will be obsolete.

The main power output is in the form of heat but a small amount of power is also output as an electrical signal.

That's because you need it in specific forms, either to transport it, or to actually use it. As an example, a hydraulic energy plant uses mechanical energy (potential energy in the water); this is converted to electrical energy, transported to our homes, and then converted to light in a light bulb (among many other uses!). In this example, we have no direct use of the potential energy as such; the energy is converted to electrical energy which is easy to transport, and easy to convert to other forms of energy - such as light in this case.

Air is a form of matter (composed of different gases, which are forms of matter).

Heat, energy, and sound are all forms of energy, not matter.

Actually, light (visible, UV, etc.) goes into solar panels, and interacts with the semiconductor (silicon) materials present, ejecting electrons via the photoelectric effect, and inducing electric current. Heat is typically in the infrared portion of the electromagnetic spectrum, and often doesn't carry the amount of energy needed to produce this effect in sufficient quantities.

Photons of light (energy) are absorbed by the silicon atoms of the solar panel, resulting in an ejection of electrons proportional to the frequency of the photons absorbed. This is called the photoelectric effect. As a large number of electrons are being ejected from atoms and set into motion, this generates an electric current. It is this electric current that can be used to power devices.

ENERGY is defined in physics as the ability to apply force. It may be the energy of matter in motion (kinetic) or at rest (potential). Or it may be a nuclear or thermal manifestation. More commonly, energy is the physical or electromagnetically-radiated release of usable power. Sources include gravity, moving water or air, converted radiation (especially solar), or chemical reactions.

A water turbine produces energy by transferring the energy from flowing or falling water using a generator. A generator uses copper coils and magnets to create energy. The magnetic field produced from the magnets need to cross over the copper coils which excite the particles in the coils to produce and cause the electricity to flow, making electricity from water.