91Ó°ÊÓ

Internal energy is a key concept in thermodynamics that describes the total energy contained within a system. This energy results from the movement and interactions of the molecules within the system. There are three main components to internal energy:

• Kinetic energy of the molecules moving around.
• Potential energy due to the forces acting between the molecules.
• Other forms of energy, such as chemical energy in bonds.

In our exercise, internal energy is involved when we calculate \( \Delta E \), which refers to the change in internal energy. The first law of thermodynamics helps us determine how internal energy changes during a process, by considering the heat added to the system and the work done by or on it. Understanding how internal energy shifts in a thermodynamic process is crucial for solving related physics problems.

Heat is the transfer of thermal energy from one system to another, resulting from a difference in temperature. In our exercise, heat is either absorbed or released by the system, impacting its internal energy.
The sign convention for heat is important in this context:

• Heat absorbed by the system is considered positive.
• Heat released by the system is considered negative.

For example, in Step 1 of the exercise, the system absorbs 72 J of heat, resulting in a positive heat value. Conversely, in Step 2, it absorbs 35 J of heat. Understanding how to account for heat transfer helps us use the first law of thermodynamics effectively in calculating changes in the system's internal energy.

Work, in the context of thermodynamics, refers to the energy transferred when a force moves an object. Work can be done on the system or by the system, and this distinction affects how we calculate changes in internal energy.
The sign convention for work is as follows:

• Work done on the system is considered negative, as it increases the system's energy.
• Work done by the system is considered positive, as it decreases the system's energy.

In Step 1 of our exercise, 35 J of work is done on the system, and is therefore negative. In Step 2, 72 J of work is done by the system, which makes it positive. By understanding how work interacts with heat in a thermodynamic process, we can accurately apply the first law of thermodynamics to calculate internal energy changes.

A thermodynamic process is a change in the state of a thermodynamic system that can involve changes in pressure, volume, temperature, or internal energy. These processes can be isothermal, adiabatic, isobaric, or isochoric, depending on the constraints involving heat transfer and work done.
The first law of thermodynamics, also known as the law of energy conservation, provides a framework for understanding these processes: \[ \Delta E = Q - W \]- \( \Delta E \) is the change in internal energy- \( Q \) is the heat added to the system- \( W \) is the work done by the system
In our exercise, this law is applied to two distinct steps to determine the overall change in internal energy. By understanding this relationships, we can predict how different actions impact the system, reinforcing the importance of the first law in analyzing thermodynamic processes.