Final answer:
In an open system, the work required to move mass across control volume boundaries is known as work, which is energy transferred by exerting force through a distance, distinct from heat transfer that's driven by temperature differences.
Step-by-step explanation:
In an open system, when mass flows across control volume boundaries, the work required to push the mass into or out of the control volume is known as work. This work can either be the work done on the system or the work done by the system. The key takeaway is that work involves a macroscopic force exerted through a distance, which is distinct from heat transfer. Heat transfer is driven by temperature differences and is a less organized process than doing work. Though both heat and work are forms of energy in transit and can change the internal energy of a system, they are not stored within the system itself. That internal energy can be altered either by heat transfer, which moves energy due to temperature differences, like the Sun warming the air in a tire, or by doing work, such as pumping air into the tire. Hence, the correct answer is: d) Work.
Heat Q and Work W
Heat and work can sometimes produce identical results, such as causing a temperature increase. However, they are fundamentally different in how they operate. While both can alter the system's internal energy, heat is energy transferred due to a temperature difference, and work is energy transferred due to the application of force through a distance. Important thermodynamic processes including isothermal and adiabatic processes can be distinguished by the way they affect heat transfer and work within a system. Both of these processes illustrate how energy interactions within a system following the first law of thermodynamics can either add or remove heat, consequently changing the system's internal energy.