Solutions

Solution

A homogeneous mixture that contains small particles ($< 1\text{ nm}$). Liquid solutions are transparent.

Solute

The substance present in a lesser amount in a solution.

Solvent

The substance present in a larger amount in a solution.

Aqueous Solution

A solution that has water as a solvent.

Colloid

A homogeneous mixture with larger particles ($1\text{ nm} - 1\ \mu\text{m}$) often having an opaque appearance. Their particles do not settle out and cannot be filtered by common filtration techniques.

Suspension

A heterogeneous mixture that contains large suspended particles ($> 1\ \mu\text{m}$) that do not dissolve. They can settle out and be separated by filtration or centrifugation.

Tyndall Effect

The scattering of light as it passes through a colloid due to small suspended particles (does not show in a true solution).

Unsaturated Solution

A solution that contains less than the maximum amount of solute that it can dissolve in a given amount of solvent at a given temperature.

Saturated Solution

A solution that contains the maximum amount of solute that it can dissolve in a given amount of solvent at a given temperature, leaving any excess undissolved substance at the bottom.

Supersaturated Solution

A solution that contains more than the maximum amount of solute that it can dissolve in a given amount of solvent at a given temperature.

Solubility

The maximum amount of solute that dissolves in a given amount of solvent (expressed in $\text{g}/100\text{ mL}$) at a given temperature.

Solvation

The interaction where solvent molecules surround and stabilize solute particles.

Miscible

Two liquids that can mix in all proportions to form a homogeneous mixture.

Immiscible

Liquids that do not form a homogeneous mixture when added together.

Concentrated Solution

A solution that has a relatively large amount of dissolved solute.

Dilute Solution

A solution that has a relatively small amount of dissolved solute.

Molarity ($M$)

The number of moles of solute per liter of solution.

Parts per Million (ppm)

A unit of concentration expressing the mass of solute per mass of solution multiplied by $10^6$ (often expressed as $\text{mg/L}$ for dilute aqueous solutions).

Parts per Billion (ppb)

A unit of concentration expressing the mass of solute per mass (or volume) of solution multiplied by $10^9$ (often expressed as $\mu\text{g/L}$).

Dilution

The process of decreasing the concentration of a solution by adding more solvent, keeping the total amount of solute constant while changing the volume.

Colligative Properties

Properties of a solution that depend on the concentration or number of particles dissolved in a solution, but not on their identity (e.g., boiling point elevation, freezing point depression, and osmotic pressure).

Freezing Point Depression

The lowering of a solvent's freezing point caused by the addition of solute particles.

Boiling Point Elevation

The raising of a solvent's boiling point caused by the addition of solute particles.

Semipermeable Membrane

A membrane with tiny pores big enough to allow solvent molecules to pass through, but small enough to block larger solute molecules, ions, and large proteins.

Osmosis

The passage of a solvent (usually water) across a semipermeable membrane from a solution of lower solute concentration to a solution of higher solute concentration.

Osmotic Pressure

The pressure necessary to prevent osmosis.

Osmolarity (osmol)

The molarity multiplied by the number of particles produced by each formula unit of solute.

Isotonic Solution

Two solutions that share the same osmotic pressure.

Hypotonic Solution

A solution that has a lower osmotic pressure than body fluids, causing water to diffuse into a cell so that it swells and eventually bursts.

Hemolysis

The swelling and rupture of red blood cells placed in a hypotonic environment.

Hypertonic Solution

A solution that has a higher osmotic pressure than body fluids, causing water to diffuse out of a cell so that it shrinks.

Crenation

The shrinking of red blood cells in a hypertonic environment.

Dialysis

The selective movement of small molecules and ions across a semipermeable membrane while retaining large molecules like proteins and starch.