10/19/16

1

DISSOLVING AND SOLUBILITY

QUICK REVIEW:

•  Homogeneous mixtures: a solution of substances in which no settling occurs (looks like one thing). A solution occurs when the particles of the components slip in between each other in an even distribution throughout the entire mixture.

•  Heterogeneous mixtures: contains two or more materials that are still visible (can see the different phases). Can be further classified based on the size of their components.

10/19/16

2

QUICK REVIEW:

•  In-Between Mixtures: ● Suspension – heterogeneous mixture in which some

particles settle after mixing (can be filtered). •  Examples: orange juice with pulp, salad dressing, paint, dust

● Colloids – heterogeneous mixture in which particles do not settle.

•  Examples: fog or hairspray (liquid dispersed in a gas), smoke or smog (solid dispersed in a gas), jelly or jello (liquid dispersed in a solid) shaving cream or whipped cream (gas dispersed in a liquid).

● Emulsion – a special colloid, with an emulsifying agent

to keep particles suspended. •  Example: mayo

WHAT MAKES MATERIALS DISSOLVE?

•  Dissolving is forming a solution by mixing two or more materials together. ● Example: salt dissolved into water.

•  But how does it dissolve?? ● Draw 4 beakers in your journal.

10/19/16

3

HOW DOES SUGAR DISSOLVE IN WATER?

•  R Remember the particle model!! Particles can attract each other and they are always moving!

WHAT MAKES MATERIALS DISSOLVE?

•  As water particles pass by the nearest (or outermost) sugar particle, the water particles can pull a sugar particle away from the other sugar particles and then the motion of the water particles carries it away. This leaves room for more water particles to move in and attract another sugar particle.

•  This process will continue until all of the sugar is dissolved. The particles will move around until they are evenly mixed throughout.

10/19/16

4

BUT WAIT…

•  What if the attraction between the different particles is stronger than the attraction bond between the same particles? ● NO DISSOLVING!!

LET’S TALK ABOUT SOLUTES AND SOLVENTS

•  A solute is the substance that dissolves in a solvent •  Example: sugar.

•  A solvent (usually more than the solute) is the substance that dissolves a solute. •  Example: water.

10/19/16

5

Example Made up of

States of Matter

Solute Solvent

Air Oxygen, nitrogen

Gas – nitrogen

Gas – oxygen

Soda water Carbon dioxide in water

Gas - carbon dioxide

Liquid - water

Vinegar Acetic acid in water

Liquid – acetic acid

Liquid – water

Ocean water

Various salts in water

Solid – salts Liquid - water

WATER = UNIVERSALLY LOVED (BY MOST SOLUTES)

•  Water : sometimes referred to as the universal solvent ●  WHY? Because it dissolves so many materials

•  Think about it: Your body is made up of a lot of water •  The water portion of your blood dissolves and transports

●  Food ●  Nutrients ●  Waste ●  Minerals ●  Vitamins

•  The same things are dissolved and transported in water in plants

10/19/16

6

MAYBE NOT SO UNIVERSAL…

•  Soluble vs. Insoluble •  If a certain solute is able to be dissolved in a particular

solvent, it is said to be soluble in that solvent. •  Soluble means able to be dissolved in a particular

solvent. •  Example: sugar is soluble in water.

•  If a certain solute is not able to dissolve, it is said to be

insoluble.

WHAT DO YOU THINK CAN INCREASE THE RATE AT WHICH SOMETHING DISSOLVES? There are many factors that can influence the rate of

dissolving of a substance: 1.  Agitation (stirring/shaking) can increase the

interactions of the solvent with the solute. It moves to fresh solvent particles close to the solute particles.

2.  Increased surface area of solute provides more area where dissolving can occur.

3.  Increased temperature increases particle movement which increases the rate of dissolving.

4.  Increased pressure moves particles closer together, increasing their interactions. Doesn’t matter much for solids and liquids but greatly affects gases.

10/19/16

7

HOW MUCH CAN BE DISSOLVED?

Solubility refers to the mass of a solute that can dissolve in a given amount of solvent to form a saturated solution at a given temperature. A saturated solution is one in which NO more solute will dissolve in a specific amount of solvent at a specific temperature. An unsaturated solution is one in which more solute could still be dissolved in that amount of solvent at that temperature.

HOW MUCH CAN BE DISSOLVED?

10/19/16

8

YOU CAN GRAPH SOLUBILITY

HOW DOES THAT LOOK ON A GRAPH?

10/19/16

9

THE LINE ITSELF ALSO REPRESENTS A “PERFECT” SOLUTION; THAT IS, A SOLUTION WITH THE EXACT AMOUNT OF SOLUTE THAT WILL SATURATE

100 ML OF WATER:

At any temperature, any LESS solute than the value on the line would produce an UNSATURATED solution à points below the line!

If 5 grams of mix were added to 40o water, the solution would not be saturated, as

shown by the point BELOW the saturation line

10/19/16

10

At any temperature, any MORE solute than the value on the line would produce an SUPERSATURATED solution à points above the line

If 70 grams of mix were added to 100o water, the solution would be more than saturated, as shown by

the point ABOVE the saturation line

BEYOND THE LIMIT

•  Supersaturated: A solution that contains more solute than would normally dissolve at a certain temperature.

10/19/16

11

WHAT ABOUT A NEGATIVE SLOPE

As temperature increases

10/19/16

12

BACK TO THE TABLE!

•  What if we want more than 100mL? Say…200mL

Amount (g) = x___ 100mL 200mL Example: salt 35.7g = x__ 100mL 200mL x = 71.4g