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a. Describe solutions in terms of• solute/solvent• conductivity• concentration

b. Explain factors affecting the rate a solute dissolves in a specific solvent.

c. Explain that solubility is related to temperature by constructing and reading a solubility curve.

Solutions Solutions GoalsGoals

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A solution is made up of two parts—a solutesolute and a solventsolvent.

A solute is the substance being dissolved, while a solvent

is the substance doing the dissolving.

For example, in a saltwater solution, salt is the solute and

water is the solvent. The ability of a substance to

dissolve in another substance is called solubilitysolubility.

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Effects of Adding a Solute to a SolventEffects of Adding a Solute to a Solvent

Freezing point

depression

Raising of the boiling

point

Adding a solute interferes with the formation of the solid making it harder for the

solvent to freeze.Ex: Antifreeze

(ethylene glycol).

Solute particles interfere with the

evaporation process and more energy is

needed for the molecules to escape into the gas phase.

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Solutions and Conductivity•Solutions can only conduct electricity if the atoms ionizeionize (break apart into ions)

•Solutions that conduct electricity are called electrolytes.

•Solutions that do not conduct electricity are called nonelectrolytes.

•They do not produce ions in solution.

Strong vs. Weak

Electrolytes

Strong: Ionize

completely. NaCl

Weak: Produce few

ions in solution.

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Factors affecting the rate a solute dissolves in a specific solvent.

What Affects the rate at which a solute will What Affects the rate at which a solute will dissolve in a solvent?dissolve in a solvent?

1.1.Crystal SizeCrystal Size

2.2.TemperatureTemperature

3.3.For Gases: For Gases: Pressure Pressure above the above the solventsolvent

Increased surface area increases the rate of

dissolving. Remember: dissolving occurs at the

surface.Increases the speed of the molecules in the solvent.

More atmospheric pressure pushing down on the

solvent makes it harder for the gas molecules to escape

the solvent.

Dissolving Website

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Factors affecting the rate a solute dissolves in a specific solvent.

Molecular Structure

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Polar Nonpolar

Polar solutes dissolve in Polar solvents

Nonpolar solutes

dissolve in Nonpolar solvents

““Like Like dissolves dissolves

like”like”

EX: Water

and HCl

EX: Gas and Oil

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To be more precise we need to express the concentration by volume. Usually as a percentage by volume.

In order to compare concentrations, we express the amount dissolved in 100g of water.

ConcentrationConcentrated Dilute

A lot of solute in a little solvent

A little solute in a lot of solvent

NOT VERY Precise!

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•As the As the temperature temperature increasesincreases......

•The amount The amount of oxygen of oxygen that is able to that is able to dissolve in dissolve in waterwater……

•decreases.decreases.

Solubility Curves9

Unsaturated Saturated Supersaturated

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Can dissolve dissolve

more more solutesolute at a

given temperatu

re

Contains all of the all of the solute it solute it can holdcan hold/

dissolve at a certain

temperature

Contains more solute more solute

that a that a saturatedsaturated

solution at a given

temperature. Can be

created by cooling a saturated solution without

disturbing it- no solute

come out of solution.

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10

20

70

80

110

50

40

30

60

20 60 80 18040 120

1.30g of KNO3 @

120˚C?

2.50g of NaCl @ 20˚C?

3.56g of NaCl @ 20˚C?

4.120g of KNO3 @ 20˚C?

5.How would you make a saturated sol. of KNO3 at 80˚C?

Solubility Curves