III. Rate of dissolving & Solubility

• A. Solubility is the ability of one thing to dissolve in another

• 1. miscible – able to dissolve• 2. immiscible – unable to

dissolve

• 3. “like dissolves like” so polar substances dissolve in other polar substances but not in nonpolar stuff

• a. salt (ionic & polar) dissolves in water (polar)

• b. vitamin k (nonpolar) dissolves in fat (nonpolar)

• c. oil (nonpolar) does not dissolve in water (polar)

Vitamins• Multi Vitamin– Provides many essential vitamins– “Expensive urine” because most is urinated

out!• Water Soluble – will dissolve in water

– Vitamin C– CAN’T be stored - must be replenished

regularly• Fat Soluble – will NOT dissolve in water (will only

dissolve in oils)– Can overdose – Vitamin A, K …– Can be ingested periodically, stored in body fat

B. Common ways to increase the rate of

dissolving• 1. Increase Temperature. Increasing

the temperature adds more energy and creates more collisions of solute and solvent to help dissolve.

• a. Ex: dissolving sugar in Warm tea vs. cold tea

• 2. Increase surface area. – Smaller pieces dissolve more quickly

because there are more places to interact between solvent and solute.

– Pulverize = crush or smash

• a. Ex: Sugar packets vs. Sugar cubes

• 3. Increase movement (stirring). • By adding motion you add kinetic

energy and move the solvent around to dissolve it.

• a. Ex: Stirring the sugar into the tea vs. letting it dissolve on its own

C. Dissolving gases follow different rules

• 1. Gases dissolved in liquids prefer lower temperatures. Cold soda has more carbonation than warm sodas

• 2. Prefer less movement, more movement lets the gas escape more easily. Shaken sodas lose the dissolved gases quickly & so have fewer bubbles.

• 3. Increased Pressure increases rate of dissolving. – So when the bottle the soda they bottle

it under higher pressure to keep the gas dissolved in it

SolubilitySolubility

Solids are more soluble at...Solids are more soluble at...• high temperatures.

Gases are more soluble at...Gases are more soluble at...• low temperatures &• high pressures• EX: nitrogen narcosis,

the “bends,” soda

IV. Concentrations of solution – how “strong” or

“weak” the solution is• A. 3 types of solutions based on

concentration of dissolved solute

• 1. Unsaturated solution – Solution that can easily dissolve more of the solute does not require an increase in temperature to add more solute.

• a. Ex. Weak sweet tea or unconcentrated acid.

• 2. Saturated solution – Solution that has the maximum amount of solute dissolved for that temperature. – Any change in temperature will affect

the concentration.

• 3. Supersaturated solution – Solution that has a higher concentration of solute than it normally would at that temperature. – It was heated up, come out of solution. – Typically can’t be disturbed or it will

crystallize.

Solubility

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute

dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

increasing concentration

• B. Solubility Chart• 1. Shows how the solubility

changes at different temps

Solubility Table

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

0 10 20 30 40 50 60 70 80 90 100

Solubility vs. Temperature for Solids

Sol

ubili

ty (

gram

s of

sol

ute/

100

g H

2O)

KI

KCl

20

10

30

40

50

60

70

80

90

110

120

130

140

100

NaNO3

KNO3

HCl NH4Cl

NH3

NaCl KClO3

SO2

shows the dependence

of solubility on temperature

gases

solids

Solubility

SolubilitySolubility

maximum grams of solute that will dissolve in 100 g of solvent at a given temperature

varies with temp

based on a saturated solution

Classify as unsaturated, saturated, or

supersaturated

per100 gH2O

80 g NaNO3 @ 30oC unsaturated

saturated

unsaturated

supersaturated

45 g KCl @ 60oC

50 g NH3 @ 10oC

70 g NH4Cl @ 70oC