Solutions Notes
Solutions
A solution is a homogeneous mixture of variable composition in a single phase.
The most abundant substance in the solution is called the solvent.
Dissolved substances are called solutes.
Ex. Kool-aid water is the solvent, Kool-aid powder is the solute
Liquid Solutions
Most solutions we use are liquid solutions.
Called a liquid solution because the solvent is a liquid.
Liquids can dissolve solids, liquids, even gases.
Water is called the universal solvent because it dissolves many different substances.
Solid and Gas Solutions
Though less common, solids can also act as solvents.
Liquids, gases and other solids can dissolve in solids. Ex. Alloys, amalgam
Gases can only dissolve other gases.
Dissolving
Solvation is the dissolving process for solid-in-liquid solutions
Occurs because the solvent separates the solute molecules.
If the solute is an ionic compound, the process is called dissociation.
In solid and gas solutions, solute and solvents mix by diffusion.
When two liquids mix, they are miscible.
If two liquids separate after mixing, they are immiscible (oil and water).
Why?
General rule: Like dissolves like.
Polar solvents dissolve polar solutes but non-polar solvents dissolve non-polar solutes.
Solubility
When a solute is able to dissolve in a solvent, it is said to be soluble.
Solubility is the maximum amount of a solute that can dissolve in a specific solvent.
When a solution contains the maximum amount of solute at a given temperature, it is
saturated.
Supersaturation
Supersaturation occurs when a solution contains more dissolved solute than it does at
equilibrium.
Example: sugar in water
Supersaturated solutions are unstable and can crystallize rapidly
Factors of Solubility
The rate at which a solute dissolves depends on its solubility and the frequency of
collisions with solvent particles.
Three factors increase the frequency of collisions
Temperature
Amount of surface area
Pressure
Temperature
In general, higher temperatures help solutes dissolve faster because it increases the
frequency of collisions.
The exception is with gases, which become less soluble at higher temperatures.
Chilling your soda will keep it fizzy longer.
Surface Area
The more surface area exposed to the solvent, the fast it dissolves.
Ex. BC Powder enters the blood stream faster than a headache pill.
Pressure
An increase in pressure of a gaseous solute increases the solubility of the gas.
Ex. Carbonated Drink – pressure is added when placed in the can to keep the CO2 in the
solution. What happens when the pressure is released?
Pressure and Scuba Divers
When divers are deep, the pressure is higher.
More nitrogen is dissolved into the blood.
If they ascend too fast, pressure decreases and nitrogen bubbles out of blood.
This causes severe pain and convulsions known as the “bends” and can be fatal.