Question

Why does osmosis occur?

Short answer

Osmosis occurs due to the passive transport of solvent molecules, typically water, across a semi-permeable membrane driven by differences in solute concentration. The semi-permeable membrane allows solvent molecules to pass while restricting solute molecules, making the process selectively permeable. Osmosis progresses until equilibrium is reached and can be explained in terms of entropy and the second law of thermodynamics. It is a crucial process in biological systems as it regulates the transport of water and other solvents across cell membranes, helping maintain homeostasis.

Step-by-step solution

Understand the concept of osmosis

Osmosis is a passive transport process in which solvent molecules move across a semi-permeable membrane, which allows the passage of solvent molecules but not solute molecules. This movement is driven by the difference in solute concentration on either side of the membrane, and it continues until equilibrium is reached.

The role of the semi-permeable membrane

A semi-permeable membrane selectively allows the passage of certain molecules while restricting the passage of others. In osmosis, water molecules are allowed to pass through the membrane, while solute molecules are not. This selective permeability is essential for osmosis to occur.

The role of solute concentration

The main driving force behind osmosis is the difference in solute concentration on either side of the semi-permeable membrane. Solvent molecules move from the area of lower solute concentration to the area of higher solute concentration in order to establish equilibrium. This process effectively dilutes the higher concentrated solution, while concentrating the more dilute solution.

Entropy and the second law of thermodynamics

Osmosis can also be understood in terms of entropy, which is a measure of randomness or disorder in a system. According to the second law of thermodynamics, natural processes tend to progress towards a state of maximum entropy. In the case of osmosis, movement of solvent molecules from low to high solute concentration increases the overall entropy of the system as it distributes the solute molecules more evenly, leading to an increase in randomness or disorder.

The importance of osmosis in biological systems

Osmosis is a fundamental process in living organisms, as it regulates the transport of water and other solvents across cell membranes to maintain homeostasis. In plants, osmosis is essential for the uptake of water and nutrients from the soil. In animals, osmosis ensures proper cell hydration and the removal of waste products from cells. The understanding of osmosis is therefore essential for the study of biology and life processes.