Question

A process which proceeds infinitesimally slowly is called (a) irreversible (b) reversible (c) isothermal (d) adiabatic

Short answer

The described process is a reversible process.

Step-by-step solution

Understanding Key Terms

Let's understand one by one what each term means. An irreversible process is a process that cannot return both the system and environment to their original states. A reversible process is a process in which the system and surroundings can be returned to the initial state from the final state without producing any changes. An isothermal process is a change of a system, in which the temperature remains constant and adiabatic process is a process in which no heat is gained or lost by the system.

Match the Given Description

Now, the question says 'a process which proceeds infinitesimally slowly'. The term 'infinitesimally slowly' suggests a process which can be reversed at any point, not causing any changes. Thus, the term which matches this description is a reversible process.

Key concepts

irreversible process

An irreversible process is one that cannot be undone by simply reversing the process path. Once it occurs, both the system and its surroundings are left altered in a way that they cannot return to the original condition without external influence or intervention.

In thermodynamics, these processes are characterized by an increase in entropy. Entropy, often viewed as a measure of disorder or randomness in a system, must inevitably increase in an irreversible process. This increase is aligned with the second law of thermodynamics, which states that the total entropy of an isolated system can only stay the same or increase.

Real-world examples of irreversible processes include:

• Mixing of two substances.
• A car moving along a road due to friction.
• Combustion in an engine.

These processes involve a loss of energy, typically in the form of heat, to the surroundings, making them impossible to reverse without external work.

isothermal process

An isothermal process is a thermodynamic process during which the temperature remains constant. It comes from the Greek words "iso," meaning "equal," and "thermo," meaning "heat."

In order for a process to be truly isothermal, two main conditions must be met:

• The system must be in contact with a thermal reservoir.
• The process must occur slowly enough to maintain thermal equilibrium.

The concept of an isothermal process is important in understanding the behavior of gases, particularly when using the ideal gas law, which is given by:\[PV = nRT\]where:

• \(P\) is the pressure,
• \(V\) is the volume,
• \(n\) is the number of moles of gas,
• \(R\) is the universal gas constant, and
• \(T\) is the temperature.

In an isothermal process, because the temperature \(T\) is constant, any change in pressure \(P\) and volume \(V\) must be inversely proportional to maintain the equality. This is particularly true for ideal gases.

a common example of an isothermal process is the slow compression or expansion of a gas within a cylinder that is in thermal equilibrium with its surroundings.

adiabatic process

An adiabatic process is a process in which there is no heat exchange between the system and its environment. This means that the system is perfectly insulated. The name "adiabatic" comes from the Greek word "adiabatos," which means impassable or not traversable, indicating the prevention of heat transfer.

This type of process is often seen in scenarios where the change is rapid, and there isn't enough time for heat exchange, such as:

• The compression or expansion of gas in a piston.
• Explosion events where gases change volumes rapidly.

During an adiabatic process, the work done by or on the system changes the internal energy of the system, which often results in a change in temperature. The relationship is given by:\[PV^\gamma = ext{constant}\]where:

• \(P\) is the pressure,
• \(V\) is the volume, and
• \(\gamma\) is the adiabatic index or heat capacity ratio.

The concept of an adiabatic process is particularly relevant in thermodynamics and meteorology, helping explain phenomena such as adiabatic cooling, where air parcels rise, expand, and cool without exchanging heat with their surroundings.