FACTORS AFFECTING SOLUBILITY 1. Temperature
Temperature has a direct effect on solubility. For the majority of ionic solids, increasing the temperature increases the rate at which the solution can be made. As the temperature increases, the particles of the solid move faster, which increases the chances that they will interact with more of the solvent particles. This results in increasing the rate at which a solution occurs.
Temperature can also increase the amount of solute that can be dissolved in a solvent. Generally speaking, as the temperature is increased, more solute particles will be dissolved. For instance, when you add table sugar to water, a solution is quite easily made. When you heat that solution and keep adding sugar, you find that large amounts of sugar can be added as the temperature keeps rising. The reason this occurs is because as the temperature increases, the intermolecular forces can be more easily broken, allowing more of the solute particles to be attracted to the solvent particles. There are other examples, though, where increasing the temperature has very little effect on how much solute can be dissolved. Table salt is a good example: you can dissolve just about the same amount of table salt in ice water as you can in boiling water.
For all gases, as the temperature increases, the solubility decreases. The kinetic molecular theory can be used to explain this phenomenon. As the temperature increases, the gas molecules move faster and are then able to escape from the liquid. The solubility of the gas, then, decreases.

2. Pressure
The second factor, pressure, affects the solubility of a gas in a liquid but never of a solid dissolving in a liquid. When pressure is applied to a gas that is above the surface of a solvent, the gas will move into the solvent and occupy some of the spaces between the particles of the solvent. A good example is carbonated soda. Pressure is applied to force the molecules into the soda. The opposite is also true. When the gas pressure is decreased, the solubility of that gas is also decreased. When you open a can of carbonated beverage, the pressure in the soda is lowered, so the gas immediately starts leaving the solution. The carbon dioxide stored in the soda is released, and you can see the fizzing on the surface of the liquid. If you leave an open can of soda out for a period of time, you may notice the beverage becoming flat because of the loss of carbon dioxide.
This gas pressure factor is expressed in Henry’s law. Henry’s law states that, at a given temperature, the solubility of a gas in a liquid is proportional to the partial pressure of the gas above the liquid. An example of Henry’s Law occurs in scuba diving. As a person dives into deep water, the pressure increases and more gases are dissolved into the blood. While ascending from a deep-water dive, the diver needs to return to the surface of the water at a very slow rate to allow for all of the dissolved gases to come out of the blood very slowly. If a person ascends too quickly, a medical emergency may occur due to the gases coming out of blood too quickly. This is called having the “bends.”

EFFECT OF POLARITY OF SOLUTE AND SOLVENT

SAMPLE | WATER | ETHANOL | HEXANE | Potassium Nitrate | soluble | insoluble | Insoluble | Sodium Chloride | soluble | insoluble | Insoluble | Ammonium Acetate | soluble | insoluble | Insoluble | Coconut Oil | immiscible | miscible | Miscible | Toluene | miscible | miscible | Miscible | Aspirin | soluble | insoluble | Insoluble |

GUIDE QUESTIONS 1. Why does the solubility of solids increase with an increase in temperature?
The solubility of a given solute in a given solvent typically depends on temperature. Many salts show a large increase in solubility with temperature. Some solutes exhibit solubility that is fairly independent of temperature. A few, such as cerium (III) sulfate, become less soluble in water as temperature increases. This temperature dependence is sometimes referred to as retrograde or inverse solubility, and exists when a salt's dissolution is exothermic; this can be explained because, according to Le Chatelier's principle, extra heat will cause the equilibrium for an exothermic process to shift towards the reactants.

2. By looking at the structure of a substance, how would you predict if it is polar or non-polar?
Examine the mixture after the two liquids have sat together for a time. If they have not separated, but have formed a solution, the unknown liquid is polar. If there is a clear boundary between the two liquids, it is non-polar.

3. What is the molecular basis of the general rule in solubility which is “Like dissolves like”?
"Like dissolves like" is an expression used by chemists to remember how some solvents work. It refers to "polar" and "nonpolar" solvents and solutes. Polar substances will dissolve in polar substances. Non-polar substances will dissolve in nonpolar substances. Non-polar substances will not dissolve in polar substances.