Lecture 4.2 – The Dissolving Process and the Rate of Dissolving
A Problem
Cools down to room
temperature
Gross!
Justify – TPS• Why does this solid appear at cold
temperatures, but it wasnt present when the cider was hot?
How does temperature, pressure, and surface area impact rate of dissolving?
I. Dissolving• We can alter the rate at which the solute
dissolves by:1. Changing the temperature2. Changing the surface area of the
solute3. Changing the pressure of the
solution.
II. Temperature and Dissolving• As you increase the
temperature, molecules start moving faster.
• By moving faster, the molecules are better able to grab the solute, form the cages around them and pull them into the solution.
• Therefore, the faster molecules are moving, the faster something dissolves.
Remember What Dissolving Looks Like?
Temperature and Dissolving Rate
Cold liquid Hot liquid
III. Surface Area and Dissolving
• As you increase the surface area, the rate at which the solute dissolves increases.
• As you increase the surface area of a substance, you are providing more sites for the solvent to interact with the solute.
Surface Area and Dissolving
Making a Carbonated Beverage
Justify – TPS
• Why does your soda become carbonated when you open it? What is happening?
IV. Pressure and Dissolving• As you increase the pressure, the rate at
which the solute dissolves increases.• The solubility and pressure relationship is
clearly seen when a gas dissolves in a liquid. • Gases can dissolve into liquids.
IV. Pressure and Dissolving• When a gas is above a liquid and the pressure
is increased, the gas molecules collide more often with the wall of the liquid and this causes more gas to be pushed into the liquid.
SUMMARIZE