Are fossil fuels are a form of mechanical energy?

Fossil fuels, e.g. carbon, methane and oil, are substances that contain energy in the form of chemical energy.

Energy is a magnitude that do not vary, this is the total amount of energy remains constant, it does not increase or decrease. Energy transforms into different forms. For example, gravitational potential energy can be transformed into kinetic energy; work can be transformed into heat.

Substances may be said to be energy because everyting contains energy, and you can say that all kind of energies are the same in the sense that they can be trasnsformed. Chemical energy may transform into light, heat, motion, and motion is mechanical energy.

So in first term fossil fuels energy is classiified as chemical energy, but in some sense you can say that all the energies are the same.

The questions about energy are more to think about the fact that the amount of energy does not change and that it can be transformed into many differente forms.

The best answer to the questions is that fossil fuels are considered chemical energy and that it may be converted into mechanical energy.
  

The charge of an ion with 55 protons and 52 electrons is +3. the reason is because protons are positive, and there are three more than the amount of negative electrons.