Molecular MixingChapter 7

Non-bonding versus Bonding Forces

Which of the following attractive forces would be the greatest:1. Ionic

2. Covalent

3. Hydrogen bonding

Essential QuestionsWhat are the forces that attract molecules to one another?

What happens when a solid dissolves into a liquid?

What determines how much of a solid will dissolve?

Essential QuestionsHow does temperature affect how much solid dissolves?

What about when gases dissolve in liquids?

How does soap work?

What does “hard water” mean?

How does a water softener work?

What are the forces that attract molecules to one another?

In pure liquids the forces are:Dipole-dipole (in polar liquids)Induced dipole-induced dipole (in nonpolar

liquids).

Think, Pair, ShareAn example of an electrostatic

attraction would be 1. Iron fillings to a magnet 2. Piece of paper to the floor3. Dust clinging to a mirror

Polar liquids

dipole – dipole attractions are the electrostatic attractions between the positive side of one molecule and the negative side of another molecule.

Nonpolar LiquidsInduced dipole-induced dipole attractions are the weak

attractions created by temporary dipoles in nonpolar molecules causing (inducing) a weak temporary dipole in a nearby molecule.

Practice PagesInduced dipole-induced dipole

attraction

How does Teflon work?

Think, Pair, ShareWhich of the two following

molecules has a greater attraction to itself? Why?

1. There are more hydrogen atoms.2. It is a bigger molecule with more electrons.3. There are more individual induced-dipole,

induced-dipole attractions.

Practice PagesAttraction in mixtures

Attractions in Mixturesion – dipole

Attractions in Mixturesdipole - induced dipole

These forces come about when the presence of a polar molecule induces (causes) a dipole to form in a nearby nonpolar molecule.

Strength of Molecular Mixing

Solutions – Key IdeasSingle-phase homogeneous mixture

can be gas, liquid, or solid

solvent and solute

Concentration

unsaturated vs saturated

solubility

Solutions are Mixtures

A physical blend of two or more substances.

Composition of mixtures can vary.

Solutions are Homogeneous Mixtures

Homogeneous Mixtures (Solutions)Uniform throughout the sample

ExamplesKool-AidGasoline

Liquid, Gas, or SolidAir is a mixture of nitrogen, oxygen, carbon

dioxide, and a few other gases.

Alloys, like 14K gold, steel, or dental fillings, are mixtures of metals.

Gasoline and rubbing alcohol are mixtures of liquids.

All of these are solutions.

Why do Solids DissolveSolids dissolve when the attractive

forces between the solvent and solute molecules exceed the attractive forces between the solute molecules.

Important ConceptIt is important to realize that when a

solid like sugar is added to water:

It may appear as if it has disappeared

Think, Pair, ShareAdding sugar to a 500 mL

container of water will cause:1.The volume to stay the same2.The volume to decrease3.The volume to increase

ConcentrationConcentration is

It is how much _______ there is in a specified ______of solution.

Concentration UnitsConcentrations are often

for example:

remember, the volume is the volume of _______, not the volume of _______.

Concentration Unitsconcentrations can be expressed as the

number of molecules of solute per volume of solution.

For this, we use a unit called the mole.

A mole is 6.02 x 1023 things. (Just like a dozen is 12 things.)

Molar ConcentrationsChemists often express concentrations

in

M

If I dissolve 6.02 x 1023 molecules of sucrose into one liter of solution

Molar Concentrations1.00 moles of sucrose weighs 342

grams, so if I dissolved 342 grams into enough water to make 1.00 liters of solution it would be 1.00 M.

Molar ConcentrationsIf I dissolved 684 grams of sucrose into

1.00 liters of solution it would be 2.00 M.M1 = M2 ; g1 = g2 L1 L2

What is the molarity if I dissolve 34.2 grams of sucrose into 1.00 liters of solution?

SolubilitySolubility is:

Saturated / UnsaturatedSaturated –

Unsaturated –

Concentration CalculationsIf I dissolve 85 grams of baking soda in

water to make 1.0 liter of solution, what is my concentration?

If I dissolved 200 g of baking soda in water to make 2.0 liters of solution, what is my concentration?

If I have 75 grams of sucrose and want to make a solution with a concentration of 125 g/liter, how much solution can I prepare?

If I want to make 500 mL of sucrose solution with a concentration of 250 g/L, how much sucrose do I need?

1.0 moles of NaOH weighs 40.0 grams.

What weight of NaOH do I need to make 200 mL of solution with a concentration of 2.0 M?

Effect of Temperature on Solubility

For most solids and liquids, solubility _________as temperature _______.

Soda StreamHow does it work?What allows the gas to dissolve in the liquid?

Effect of Temperature on Solubility

For gases dissolved in liquids, solubility __________as temperature increases.

For gases dissolved in liquids, solubility __________as pressure increases.

Soap and DetergentsHow do soap and detergents work?

The carbon and hydrogen atoms form the non-polar tail

The carbon and oxygen atoms form the polar head.Dirt is surrounded by Water is attracted to

DetergentsDetergents are synthetic soaps

Were created during the 1940’s as an

Stronger attraction to grease and

Hard Water & Soap

Water-softening Agents

Water Softener Resin Bead

What are the forces that attract molecules to one another?

ion – dipole

dipole - dipole

dipole - induced dipole

induced dipole- induced dipole(temporary dipoles)