Types of energy and work I am learning about energy and work, and am a beginner to this topic. Energy is defined as the ability to do work. In some cases, the ability to do work directly follows the type of energy. For instance, heat energy can be used to do work through isothermal expansion of gas, for instance.
Is there a relationship/concept between how easy it is to get a type of energy to do work? Some types of energy might make them more suitable to do work, whereas others might involve a more indirect/contrived route.
 A: Energy defined as the ability to do work; this does not mean that only work is done, it means that work can be done.
Here is an expanded definition that should help.
The energy of a system is a property of the system that is increased (decreased) by the following mechanisms:

*

*work done on (or done by) the system from its surroundings


*heat added to (or removed from) the system from its surroundings


*mass transfer into (or from) the system to its surroundings.
"How easy it is to get a type of energy to do work" depends how the system interacts with the surrounding.
For example, if a system comprised of a gas has a higher pressure than its surroundings and can move a boundary (say a piston), the system can lose energy by doing work on the surroundings as the gas expands.  Or if the gas is in a closed container (fixed volume) and has a higher temperature than its surroundings, the gas can lose energy by transferring heat to the surroundings.  A liquid can have a decrease in its energy, with a decrease in its temperature, by evaporation (mass transfer from the liquid).
The details of energy transfer is addressed by the laws of thermodynamics (e.g., the first and second laws).
