Question

When osmosis occurs between two solutions of different concentrations, what would you observe about each solution? Explain your observations in terms of molecular motion.

Short answer

When osmosis occurs between two solutions of different concentrations, you would observe a decrease in the volume of the less concentrated solution and an increase in the volume of the more concentrated solution. This is due to the movement of solvent molecules from the area of lower solute concentration to the area of higher concentration, in an attempt to establish equilibrium. This movement is caused by the random motion of the solvent molecules, which have a higher probability of moving from the less concentrated to the more concentrated solution due to their higher number in the former.

Step-by-step solution

Understanding Osmosis

Osmosis is the movement of solvent molecules from a region of lower solute concentration to a region of higher solute concentration through a semi-permeable membrane. This means that, in context of this exercise, when a solvent is in contact with two solutions of different concentrations, solvent molecules will move from the solution with less solute to the one with more until equilibrium is established.

Observing Changes in the Solutions

If one were to observe two solutions of different concentrations undergoing osmosis, they would note a few changes. The volume of the solution with a lower concentration (hypotonic solution) would decrease, while that of the solution with a higher concentration (hypertonic solution) would increase. This is due to the solvent moving from the hypotonic to the hypertonic solution in an attempt to establish equilibrium. Ultimately, this movement would continue until both solutions reach an isotonic state, or equal concentrations.

Explaining Observations in terms of Molecular Motion

The motion of molecules explains this phenomenon. Solvent molecules are always in random motion due to their kinetic energy, which can cause them to collide with the membrane separating the two solutions. As there are more solvent molecules on the side of the hypotonic solution, the probability of these molecules striking the membrane and passing to the hypertonic side is higher. This is what causes the net movement of solvent from the hypotonic to the hypertonic solution, eventually leading to a state of equilibrium.

Key concepts

Molecular Motion

Molecular motion refers to the constant and random movement of molecules in a substance. This movement arises from the kinetic energy inherent in the molecules themselves. In the case of osmosis, this motion plays a crucial role.
Solvent molecules, like water, move incessantly and collide with one another and any barriers they encounter. Their kinetic energy propels them in various directions, allowing them to transfer from areas with high molecular abundance, or lower solute concentrations, to higher solute concentrations.

• This movement is essential for processes like osmosis, which attempt to balance solute distributions across membranes.
• Temperature is a key factor as higher temperatures can increase molecular motion.

Understanding molecular motion helps in grasping why and how equilibrium is achieved during osmosis. Warmed solvents increase molecule speed, enhancing their motion and potential movement across semi-permeable membranes.

Semi-permeable Membrane

A semi-permeable membrane is a selective barrier allowing certain molecules to pass through while restricting others. In the context of osmosis, it plays a pivotal role by permitting the passage of solvent molecules such as water, while typically restricting solute molecules like salts or sugars.
This selectivity is due to the membrane's structure, which may include pores or channels that are specific in size and charge.

• These membranes are important in biological processes, for example, cell walls that regulate osmosis in living organisms.
• They help maintain the balance and concentration of solutes within cells and their surrounding environments.

By understanding the functionality of semi-permeable membranes, one can appreciate how they facilitate processes like osmosis and influence equilibrium between hypotonic and hypertonic solutions.

Hypotonic and Hypertonic Solutions

Hypotonic and hypertonic solutions are terms used to describe the concentration of solutes in different solutions. A hypotonic solution has a lower concentration of solutes compared to another solution, while a hypertonic solution has a higher concentration.
During osmosis, water, as a solvent, moves from the hypotonic solution, where solute concentration is lower, to the hypertonic solution, where it is higher. This movement aims to equalize solute concentration on both sides of a membrane.

• In the case of cells, if placed in a hypotonic environment, they might swell due to water intake.
• Conversely, a cell in a hypertonic environment may shrink as water leaves.

Understanding these terms helps in explaining how cells and organisms regulate their internal environments through osmosis, and why changes in concentration gradients are crucial for cellular function and overall homeostasis.