Solubility and the Dissolving Process

Chapter 7.2 and 7.3

What is solubility?

• The amount of solute that will dissolve into a solvent (at a certain pressure and temperature)

• Remember, solute is the smaller amount of a substance and the solvent is the larger portion of what is combined

Different substances have different solubilities…

• Solubilities of some ionic compounds in water

How to describe how much solute is dissolved in the solvent…

• Concentration—the amount of a particular substance in a solution – Large amount of solute = concentrated solution– Small amount of solute = dilute solution

How concentrated are solution?

• Saturated solution—a solution that cannot dissolve anymore solute into it (It’s full!)

• Unsaturated solution—a solution where more solute can still be dissolved into it (“contains less solute than the saturated solution”)

Temperature… • The solubility increases as the temperature of

the solution increases (if you heat up the solution, more can be dissolved into it!)

• Supersaturated solution—a solution that holds more dissolve solute than the regular equilibrium saturated state

How to make a crystal…• Heat up a solution, dissolve more solute in

than can normally dissolve, then cool back down the solution

• Add one extra bit of solute (a crystal of solute”) and the whole solution and extra solute will crystallize out!

What affects the dissolving process?

• Stirring or shaking (helps solute dissolve faster by bumping them against the solute particles faster)

• Heating up the solvent (particles move faster with more energy)

• Larger surface area increases dissolving rate (more area of the solute to interact with the solvent)

Solute affect the physical properties of solutions…

• Adding solute will cause…– The boiling point of a solution to increase (boiling

point elevation) – The freezing point of a solution to decrease

(freezing point depression)• So, instead of water freezing at 0 degrees Celsius, it

freezes at -15 degrees Celsius.

Your mission…• …if you choose to accept it….