tEMPERATURE+AND+pRESSURE+EFFECTS+ON+SOLUBILITY

The solubility of solutes is dependent on temperature. When a solid dissolves in a liquid, a change in the physical state of the solid analogous to melting takes place. Heat is required to break the bonds holding the molecules in the solid together. At the same time, heat is given off during the formation of new solute -- solvent bonds. If the heat given off in the dissolving process is greater than the heat required to break apart the solid, the net dissolving reaction is exothermic (energy given off). The addition of more heat (increases temperature) inhibits the dissolving reaction since excess heat is already being produced by the reaction. This situation is not very common where an increase in temperature produces a decrease in solubility. If the heat given off in the dissolving reaction is less than the heat required to break apart the solid, the net dissolving reaction is endothermic (energy required). The addition of more heat facilitates the dissolving reaction by providing energy to break bonds in the solid. This is the most common situation where an increase in temperature produces an increase in solubility for solids. The use of first-aid instant cold packs is an application of this solubility principle. A salt such as ammonium nitrate is dissolved in water after a sharp blow breaks the containers for each. The dissolving reaction is endothermic - requires heat. Therefore the heat is drawn from the surroundings, the pack feels cold. The variation of solubility for a gas with temperature can be determined by examining the graphic on the left. As the temperature increases, the solubility of a gas decrease as shown by the downward trend in the graph. More gas is present in a solution with a lower temperature compared to a solution with a higher temperature. The reason for this gas solubility relationship with temperature is very similar to the reason that vapor pressure increases with temperature. Increased temperature causes an increase in kinetic energy. The higher kinetic energy causes more motion in molecules which break intermolecular bonds and escape from solution. This gas solubility relationship can be remembered if you think about what happens to a "soda pop" as it stands around for awhile at room temperature. The taste is very "flat" since more of the "tangy" carbon dioxide bubbles have escaped. Boiled water also tastes "flat" because all of the oxygen gas has been removed by heating. 5 EXTRA POINTS WILL BE ADDED TO SOLUBILITY TEST FOR CORRECT ANSWERS.
 * Effect of Temperature on Solubility: **
 * CASE I: Decrease in solubility with temperature: **
 * CASE II: Increase in solubility with temperature: **
 * Solubility of Gases vs. Temperature:**
 * Quiz: Thermal pollution is merely waste heat that has been transferred to water or air. How is the concentration of dissolved oxygen in water be effected by thermal pollution?**