# Irreversible processes. Heat equation, diffusion equation

• A
• Higgsono
In summary, irreversible processes are reactions that cannot be reversed and cause a permanent change in the system. The heat equation is a mathematical expression that describes the flow of heat in a system, while the diffusion equation describes the movement of particles from high to low concentration. These two equations are related in that the heat equation helps to describe the transfer of heat in irreversible processes. However, they differ in the factors they consider, with the diffusion equation focusing on concentration gradients and the heat equation focusing on temperature differences.
Higgsono
Both the heat equation and the diffusion equation describe processes which are irreversible, because the equations have an odd time derivative. But how can these equations describe the real world when we know that all processes in nature are reversible, information is always conserved? But these equations seems to describe processes in which information is not conserved.

Who says all processes in nature are reversible?

Chestermiller said:
Who says all processes in nature are reversible?

Because microscopically all processes have a time reversal symmetry.

## 1. What are irreversible processes?

Irreversible processes are physical or chemical processes that cannot be reversed or undone. This means that once the process has occurred, it cannot be reversed back to its original state.

## 2. What is the heat equation?

The heat equation is a partial differential equation that describes the distribution of heat in a given region over time. It takes into account factors such as temperature, thermal conductivity, and heat sources or sinks.

## 3. How is the heat equation used in science?

The heat equation is used in various fields of science, such as physics, engineering, and chemistry, to model and predict the transfer of heat in different systems. It is also used in solving problems related to heat conduction, diffusion, and thermal equilibrium.

## 4. What is the diffusion equation?

The diffusion equation is a partial differential equation that describes how a substance or quantity, such as heat or mass, diffuses or spreads out over time in a given region. It takes into account factors such as concentration, diffusion coefficient, and sources or sinks.

## 5. How is the diffusion equation related to the heat equation?

The heat equation and the diffusion equation are closely related, as they both involve the transfer of a quantity (heat or mass) in a given region over time. In fact, the heat equation can be derived from the diffusion equation by considering the specific case of heat diffusion.

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