Question

What is the law of conservation of energy? How does it relate to energy exchanges between a thermodynamic system and its surroundings?

Short answer

The law of conservation of energy states that the total energy of an isolated system remains constant. In a thermodynamic system, this law implies no net change in energy during energy exchanges with surroundings; instead, energy is transferred or transformed.

Step-by-step solution

Defining the Law of Conservation of Energy

State the law of conservation of energy, which asserts that the total energy of an isolated system remains constant—it is said to be conserved over time. Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another.

Understanding Thermodynamic Systems

Explain what a thermodynamic system is—a body of matter and/or radiation, confined in space by physical boundaries, which may exchange energy with its surroundings.

Describing Energy Exchanges

Describe how the law of conservation of energy pertains to energy exchanges in a thermodynamic system. The total energy of a system and its surroundings is conserved. When a system undergoes a process, energy can be transferred to or from its surroundings, typically as heat or work, but the total energy remains unchanged.

Key concepts

Thermodynamic Systems

Understanding thermodynamic systems is crucial when studying energy and its behavior. A thermodynamic system refers to any region of space containing matter and energy that can interact with its environment. This could be as simple as a single atom or as complex as an entire star. Boundaries of a thermodynamic system can be physical, such as the walls of a gas container, or imaginary, like the borders outlining a system in a diagram.

There are different types of thermodynamic systems, with the main ones being:

• Isolated systems: These do not exchange energy or matter with their surroundings.
• Closed systems: These exchange energy (like heat or work) but not matter with their environment.
• Open systems: These exchange both energy and matter with their surroundings.

For instance, if you're boiling water on a stove, the pot with water is considered a thermodynamic system. It exchanges heat with its surroundings (the stove and air), illustrating a practical example of thermodynamic properties and interactions.

Energy Transformation

The essence of energy transformation is a fundamental principle that manifests in various phenomena of physics. It's the process by which energy changes from one form to another. Common forms of energy include kinetic, potential, thermal, electrical, chemical, and nuclear energy. In a thermodynamic context, these transformations are dictated by the surroundings and the laws of thermodynamics.

Take for example a hydroelectric dam. Gravitational potential energy of water stored at height transforms into kinetic energy as the water flows down due to gravity. When it hits the turbine blades, this kinetic energy then transforms into mechanical energy, which subsequently is transformed into electrical energy by a generator. Throughout this entire process, while the form of energy changes, the total amount of energy remains constant, adhering to the law of conservation of energy.

Energy Exchanges

In regards to energy exchanges, these are interactions where energy moves between a system and its surroundings. Understanding these exchanges is vital in the science of energy conservation.

Energy can be exchanged in forms such as heat or work.

Heat Exchange

Heat typically flows from a hotter to a cooler object. This is what happens when you place a cold spoon in a hot cup of tea; the spoon heats up by absorbing heat energy from the tea.

Work Exchange

Work, on the other hand, involves the transfer of energy through force applying over a distance, such as when you wind a watch and the spring stores energy.
It’s essential to note that during these exchanges, although energy might appear to be 'used' or 'lost' - such as heat lost to the atmosphere when boiling water - it is actually always conserved within the larger system that includes both the thermodynamic system and its environment, illustrating the relentless persistence of the conservation of energy as a cornerstone of physical sciences.