It’s Friday! Air Bag Testing

You need out your air bag lab from yesterday. Continue working with your partner on the

calculations. You have 20 minutes to calculate AND test (you have two trials) your simulation

air bag.

Vocabulary Slides: http://goo.gl/eju5D1

Vocabulary:Solute

Solvent

Solution

solvation

Homogeneous mixture

Heterogeneous mixture

Tyndall effect

Chromatography

Distillation

Filtration

Evaporation

Magnetic separation

Alloy

Colloids

Suspensions

Aqueous

Soluble

Insoluble

Concentration

Electrolyte

Nonelectrolyte

Miscible

immiscible

Unsaturated solution

Supersaturated solution

Saturated solution

solubility curve

Concentrated

Dilute

Dilution

molarity

freezing point depression

boiling point elevation

osmotic pressure

vapor pressure

Matter

Pure Substances

Mixtures

Elements Compounds

Homogeneous Mixtures

(Solutions)

Heterogeneous Mixtures

What is a solution?

The amount of a substance that dissolves in a given volume of solvent at a given temperature

A solution in which the solvent is water

What is solubility?

What is an Aqueous Solution?

The other substances –smaller amount What is a solute?

What is a solvent?

A homogenous mixture, in which the components are uniformly intermingled.

The substance present in the largest amount

Definitions Solution - homogeneous mixture

Solvent - present in greater amount

Solute - substance being dissolved

Solvation

NONPOLAR

NONPOLAR

POLAR

POLAR

“Like Dissolves Like”“Like Dissolves Like”

Miscible

Two substances that are miscible are soluble together and will mix. Water and alcohol for example.

Immiscible

Two insoluble liquids, they will not mix together. Oil and water for example.

What causes miscibility?

Polarity!

Like dissolves like – polar dissolves in polar – nonpolar dissolves in nonpolar

Salt (very polar) dissolves in water (polar)

Oil (nonpolar) doesn’t dissolve in water (polar)

SurfactantSoap/Detergent

polar “head” with long nonpolar “tail”dissolves nonpolar grease in polar water

Classification of Liquid Mixtures

Mixtures that are mostly liquid can be classified as three different things…

1. Solution (homogeneous mixture)

2. Colloid (type of heterogeneous mixture)

3. Suspension (type of heterogeneous mixture)

Simple tests can help determine what type of mixture you have.

SolutionsMade up of two parts

Solute (what there is less of)

Solvent (what there is more of)

If you make sugar water, what is the solvent and what is the solute?

SolutionsMade up of two parts

Solute (what there is less of)

Solvent (what there is more of)

If you make sugar water, what is the solvent and what is the solute?

Solvent – water

Solute - sugar

Solutions - Properties

Clear (see-through), but not necessarily colorless.

Solutions - Properties

Solute particles are ions or molecules with a size less than a nanometer (1 x 10-9 m) – very small!

Particles cannot be seen even with a microscope, and the mixture doesn’t scatter light.

Solutions - Properties

Cannot be separated by filtering, settling, or centrifuging.

Solutions - Properties

Can conduct electricity (but don’t always – remember ionic vs. covalent)

Examples of solutions – salt water, soft drinks, kool-aid

Can you think of any others?

ColloidsA heterogeneous mixture because the particles dispersed throughout the liquid can be seen with a microscope.

The particles in a colloid are bigger than the particles dispersed in a solution.

Colloids - Properties

Can appear clear, slightly cloudy, or very cloudy.

Colloids - Properties

They scatter light. This is called the Tyndall Effect.

Colloids - Properties

Dispersed particles are about 10-100 times bigger than the particles dissolved in solutions.

Will not conduct electricity.

Colloids - Properties

Will not separate into separate parts by settling, standing, or filtering.

Can be separated by centrifuge or heating, depends on the specific colloid.

Colloids, Examples

Fog, jello, homogenized milk..

Can you think of any others?

SuspensionsLarge particles dispersed in liquid – can be seen with a light microscope and sometimes the naked eye.

Suspensions - Properties

Cloudy when shaken, but the dispersed particles settle upon standing.

Can speed separation by filtering or centrifuging.

SuspensionsWill not conduct electricity.

Suspensions - Examples

Muddy water, raw milk (cream separates out on its own), sandy water..

Can you think of others?

How do we know if the

products of a chemical

reaction are (aq), a solution

or (s), a suspension or a

precipitate?

Separation of Mixtures:Other types must be separated through

various processes.

Chromatography (based on polarity)

Filtration (based on particle size)

Centrifugation Distillation (based on boiling point) and Desalinization

Separation of Mixtures:

Type Process?????

Pond Water?????

Water + Dirt

????Blood

???????????

?????Ocean Water

????? and Desalinization??????

Separation of Mixtures:

Type ProcessSuspensionPond Water

FiltrationWater + Dirt

ColloidBlood

CentrifugationSerum + Blood Cells

SolutionOcean Water

Distillation and DesalinizationWater + Salt

Solvation Solvation – the process of dissolving

solute particles are separated and pulled into solution

solute particles are surrounded by solvent particles

ElectrolytesSome solutions can conduct electricity. These are called electrolytes.

Either ionic compounds or highly polar compounds can act like electrolytes.

Ionic Ex: NaCl splits in water to form Na+ and Cl-. The ions carry the current.

Highly Polar Ex: HCl in water is able to split into Cl- and H+ (which attaches to water to form H3O+). These charged particles carry the current.

Solvation & Electrolytes

StrongElectrolyte

Non-Electrolyte solute exists

asions only

- +

salt

- +

sugar

solute exists asmolecules only

- +

acetic acid

WeakElectrolyte

solute exists asions andmolecules

DISSOCIATION IONIZATION

Ionization – a molecular compound that is soluble

based on its polarity

Dissociation – an ionic compound that is soluble

NaCl(s) Na+(aq) + Cl–(aq)

HNO3(aq) + H2O(l) H3O+(aq) + NO3–

(aq)

Three categories of Strong Electrolytes

1. Strong Acids

2. Strong Bases

3. Soluble Salts (ionic compounds)

1. Strong AcidsHCl, HBr, HI, H2SO4, HNO3, HClO4, HClO3

These need to be memorized.

2. Strong BasesHydroxides of group I and II. (Except Be(OH)2 and Mg(OH)2 – these remain mostly solid)

These also need to be memorized

Soluble SaltsCOMPOUNDS OF THESE IONS ARE ALWAYS SOLUBLE

EXCEPT WITH

NO3-, Group I, NH4

+, C2H3O2-, ClO4

-, ClO3

-

No exceptions

Cl-, Br-, I- Pb+2, Ag+1, Hg2+2

SO4-2 Pb+2, Ag+, Hg2

+2, Ca+2, Sr+2, Ba+2

•If a compound does not fit into one of the three categories above, assume it is insoluble and a nonelectrolyte (fix this in your notes).

•Also – gases, pure liquids, and solids are nonelectrolytes. (but gases can be dissolved in water)

SolubilitySATURATED SOLUTIONno more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTIONbecomes unstable, crystals form

concentration

Saturated Solution:

Saturation of a solution is sort of like saturation of a sponge. There are only so many holes in a sponge to hold a liquid, and when it is full there is simply no more room.

Magnified Sponge (x40)

Unsaturated Solution An unsaturated solution

is like a sponge that can hold more water.

More solute can be dissolved at that temperature.

I’m still thirsty!

Supersaturated Solution

Can be prepared by

changing the conditions

of a saturated solution

(temperature, volume,

or pressure).

A supersaturated solution is a solution that contains more of the solute than it can normally hold.

How is Solubility Expressed?

_____ g / 100g of water at ____ °C

Solvent Temperature

Solubility is the amount of a substance that can be dissolved in a liquid under specified conditions.

Solute

How is Solubility Expressed?

_____ g / 100g of water at ___ °C

Control Independent Variable

(CAUSE)

Dependent Variable

(EFFECT)

SolubilityEx: 80 grams of KNO3 will dissolve in 100 grams of water at 50 degrees Celsius.

This is the maximum amount.

Called “saturation”

SolubilityUnsaturated is when more solute could dissolve.

Ex: 70 grams of KNO3 dissolved in 100 grams of water at 60 degrees Celsius.

Any point below the line is unsaturated. You could dissolve more.

SolubilitySupersaturated is when more is dissolved than normally could be.

Ex: 110 grams of KNO3 dissolved in 100 grams of water at 60 degrees.

Any disturbance or seed crystal will cause the excess to precipitate out.

How much will ppt out in this situation?

Review What We’ve Learned

Solutions that are described by the line are always SATURATED SOLUTIONS.

Solutions that are above the line are always SUPERSATURATED SOLUTIONS.

Solutions that are below the line are always UNSATURATED SOLUTIONS.

Practice

How much KClO3 could possibly dissolve at 70 oC?

Which compound is least soluble at 40 oC?

How many grams of NaCl could dissolve at 10 oC?

Practice

90 grams of sodium nitrate is dissolved in 100 grams of water at 30 oC. The solution is ____.

Which substance is least soluble at 0 oC?

Solubility Trends Seen..

Solids become more soluble as temperature increases.

Gases become less soluble as temperature increases.

Solubility Curve:____ g / 100g of water at

____ °C

What if we change the amount of water?

Think About It:If we make one pack of Kool-Aid, we will need 2 quarts of water.

If we make two packs of Kool-Aid, and we want it to have the same concentration as a 1 pack Kool-Aid solution, how much water would we need?

Solubility CurveIn order to reach saturation, if we double the amount of water that is being used to prepare the solution, we would need to also double the solute.

20 g / 100g of water at 25 °C

40 g / 200g of water at 25 °C

How many grams of ammonia could dissolve in 200 grams of water at 50 oC?

If 95 grams of NaCl is dissolved in 200 grams of water at 90 oC, is the solution saturated, unsat, or supersat?

Measuring the Concentration of

Solutions

MolarityThe molarity of a solution is a measure of how many moles of solute are present for each liter of solution. The higher the molarity, the more concentrated a solution is.

Molarity (M) = mol solute

L solution

Molarity is useful in stoichiometric problems.

Molality – another measure of concentration

Molality is the concentration of a solution calculated by dividing the number of moles of solute by kilograms of solvent (usually water) used to dissolve.

m = mol solute

kg solvent

This measurement is useful for something else – calculating how boiling and freezing temperatures changes as you add solute to solvent.

Mole Fractionanother measure of

concentration

Say you have a solution made of component 1 and component 2

Mole fraction for component 1 of solution = moles of component 1

total moles of all components

In other words:

X = 1

1+2 THIS IS A FRACTION SO THERE ARE NO UNITS

Percent MassThe last measure of concentration!

% mass = grams component x 100

grams of mixture

DilutionsFrequently it is necessary to dilute a more concentrated solution to produce the needed concentration in the lab.

I may have 18 molar sulfuric acid, but I need only a small amount of 1 molar.

Dilutions FormulaM1V1 = M2V2

M is molarity

V is volume

1 is initial (higher concentration)

2 is final (diluted concentration)

Colligative Properties of Solutions

Colligative Properties

Properties of a solution that depend on the amount of solute particles the type of particle doesn’t matter.

Freezing Point Depression

By adding a nonvolatile solute, we can change a solvent’s freezing point and boiling point.

Nonvolatile – doesn’t evaporate easily.

Freezing Point Depression

Antifreeze

Salt on iced over bridges

ΔT = Kfmi

ΔT = change in FP temperature

Kf = molal freezing point constant (-1.86 for water)

m = molality (mol solute / kg solvent)

i = number of ions

Boiling Point Elevation

Boiling point can be increased by adding a nonvolatile solution, and the “elevation” or number by which the BP is elevated, can be calculated.

Boiling Point Elevation

Cooking with boiling water

ΔT = Kbmi

ΔT = change in BP temperature

Kb = molal boiling point constant (0.51 for water)

m = molality (mol solute / kg solvent)

i = number of ions

If the solute is ionic & soluble.. It breaks into ions.

You have more particlesIf the solution has an ionic compound, it has more than one particle per formula unit.

Ex: MgCl2 (s) Mg+2 (aq) + 2Cl- (aq)

Three particles are present, so the change in temperature is tripled.

ΔTb = iKbm

ΔTf = iKfm

i = number of ions in the formula.

Vapor Pressure Lowering

The vapor pressure of a liquid is the pressure due to evaporated liquid in a closed container.

Decreasing Vapor Pressure

Adding a nonvolatile solute lowers the vapor pressure because surface area available for evaporation is limited.