1

SolutionsWhy Does Pasta Expand When Cooked?

Why does Lemon Juice sting?Why Do Salt Grains Dissolve?

2

How Do Solutions Form?

Polar molecules pull polar molecules apart

Water molecules break up the salt crystals

3

Polar Molecules

• Salt Crystal • Water molecules attracting sodium

4

Some DefinitionsA solution is a mixture of 2 or

more substances. The substance that dissolves the

others is the SOLVENT.The substance that dissolve into

the solvent are SOLUTES.

Example: Salt WaterWater = Solvent Salt = Solute

5Solute Solvent Example

Solid Solid Alloys

Bronze is copper and tin

Liquid Liquid Liquor

Ethanol dissolved in water

Gas Liquid Carbonated Water

Carbon Dioxide in Water

Gas Gas Air

Oxygen and other Gasses in Nitrogen

6

DefinitionsSolutions can be classified as

saturated or unsaturated.

An unsaturated solution contains less than the maximum amount of solute.

That means you can dissolve more at that particular temperature

7

DefinitionsSolutions can be classified as

saturated or unsaturated.

A saturated solution contains the maximum quantity of solute that dissolves at that temperature.

If it gets too saturated, crystals will form and drop out of solution.

8

How Temperature Affects Solubility• More can dissolve in hot fluids than cool fluids.• That is why you heat water to dissolve sugar or

other substances into them.• At cooler temperatures, the crystals will just

drop to the bottom.• If it is saturated and you cool it down, crystals

will drop out of solution.

9

DefinitionsSUPERSATURATED SOLUTIONS

contain more solute than is possible to be dissolved

Supersaturated solutions are unstable and temporary

Any disturbance, including shaking, stirring, or adding more solute will cause it to come out of solution.

10

SupersaturatedSodium Acetate

• One application of a supersaturated solution is the sodium acetate “heat pack.”

• Click on the metal piece inside and it instantly precipitates

11

How do we know ions are present in aqueous solutions?

ELECTROLYTESThey conduct

electricity

HCl, MgCl2, and NaCl are strong electrolytes.

They dissociate completely (or nearly so) into ions.

Aqueous Solutions

12Aqueous Solutions

Some compounds dissolve in water but do not conduct electricity.

They are called nonelectrolytes.

These are usually covalent compounds, not ionic

Examples include:sugarethanolethylene glycol

13

Electrolytes in the Body

Carry messages to

and from the brain

as electrical signals

Maintain cellular

function.

Make your own50-70 g sugarOne liter of warm waterPinch of salt200ml of sugar free fruit

squashMix, cool and drink

14Changing Physical Properties

On adding a solute to a solvent, the properties of the solvent are modified.

• Vapor pressure decreases• Melting point decreases• Boiling point increases• Osmosis is possible (osmotic pressure)

They depend only on the NUMBER of solute particles relative to solvent particles, not on the KIND of solute particles.

15

Change in Freezing Point

The freezing point of a solution is LOWER than that of the pure solvent

Pure water Ethylene glycol

16Change in Freezing Point

Common Applications of Freezing Point Depression

Propylene glycol

Ethylene glycol – deadly to small animals

17

Properties of Acids

• Sour Taste

• Litmus paper turns red

• Reactivity with Metals

18

Properties of Bases

• Bitter Taste

• Litmus paper turns blue

• Slippery Feel

• Corrosive

19Definitions:

An acid is a substance that increases the H+ (or H3O+) concentration in an aqueous solution. Also known as proton donors.

HCl + H2O

A base is a substance that increases the OH- concentrationin an aqueous solution. Also known as proton acceptors.

H+ + H2O + Cl-

H3O+ + Cl-

NaOH(s) Na+ + OH-

20

pH Scale

21

Why is Sea Water Basic?

Alkaline substances such as limestone dissolve from rocks, head down rivers, and are deposited

in the sea

Coral, clams, snails, and others make their shells from the calcium dissolved in sea water

22

Ocean AcidificationThe pH of the ocean is becoming more acidic with global warming.

That is because more CO2 is dissolving into the ocean as more if released by humans into the atmosphere

This makes it more difficult for sea creates with calcium shells to survive

Their calcium shells dissolve in the acidic water

Coral reefs are being destroyed and the ocean ecosystems affected.

23

Acid/Base reactions (neutralization):Produce water and a salt (and sometimes carbon dioxide).

Hint: concentrate on the water first. Remember, water has the formula HOH.

Complete and balance the following:

HCl + KOH

HCl + Ca(OH)2

H2O + KCl

2

Require equal numbers

2HOH + CaCl2