SECTION 3-2Concentration and Solubility

Objectives L.3.2.1. Describe how

concentration is measured. L.3.2.2. Explain why solubility is

useful in identifying a substance. L.3.2.3. Identify factors that affect

solubility.

Concentration of a Solution In a dilute solution

the mixture only has a small amount of solute. What does this mean about the amount you can add?

It means you can add a lot more.

In a concentrated solution the mixture has a lot of solute. What does this mean about the amount you can add to it?

It means you can’t add much more, if any.

Dilute to Concentrated

Measuring Concentration The best way to

measure concentration is the mass of the solute divided by the mass of the solution times 100%. Objective L.3.2.1.

How To Measure Concentration

How Can We Decrease Concentration?

Add more Solvent or Remove solute

How Can We Increase Concentration?

Remove Solvent or Add more solute

Solubility Solubility is the measure of how much

solute can dissolve in a solvent at a given temperature.

If the solvent is full of solute and can not hold any more then it is saturated.

If you can add more solute and it will continue to dissolve then the solution is unsaturated.

Using Solubility Solubility can be used to

help identify a substance because it is a characteristic property of matter. Objective L.3.2.2.

Factors That Affect Solubility Temperature Pressure Type of Solvent Objective L.3.2.3.

Solubility In Water Based On Temperature

Direct Relationship Indirect Relationship

Solubility of solids in water usually increases as temperature increases.

Solubility of gases in water usually decreases as temperature increases.

Solubility In Water Based On Temperature

Sugar Carbon Dioxide

Pressure High pressure

can increase solubility of gases in water because the pressure allows more gas to stay in solution.

Solvents Sometimes you

cant make a solution because the substances are not compatible like oil and water.

Like Dissolves Like Ionic and polar

covalent substances dissolve in polar solvents like water. This is because of the positive and negative charges in these substances.

Supersaturated Solution If a heated solution

is cooled, sometimes the extra solute will stay dissolved. This is called a supersaturated solution and it’s how candy is made.

Mass % Solution