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Solutions•I will describe and categorize solutions•I will calculate concentrations of solutions•I will analyze the colligative properties of solutions•I will compare and contrast heterogeneous mixtures

What are Solutions?

I will describe the characteristics of solutions and identify the various types

I will relate intermolecular forces and the process of solvation

I will define solubility and identify factors affecting it

Parts of a Solution

Solute Substance that dissolves

Solvent Dissolves the solute Water is the most common

Solutions are also known as homogeneous mixtures!

Solution Vocabulary

Soluble A substance that dissolves in a solvent Sugar is soluble in water

Insoluble A substance that does NOT dissolve in a solvent Sand is insoluble in water

Immiscible Any two liquids that can be mixed together but separate

shortly after you cease mixing them Oil and Vinegar are immiscible

Miscible Any two liquids that are soluble in each other Water and ethylene glycol are miscible (antifreeze)

Characteristics of Solutions

It is NOT possible to distinguish the solvent from solute

Exist as solid, liquid (most common), or gas Depends on state of solvent

Examples Gas = air (oxygen, nitrogen, argon, carbon dioxide, etc) Solid = braces (titanium and nickel) Liquids = sugar water

Types of Solutions

Gas Gas in Gas—air (nitrogen + oxygen)

Liquid Gas in Liquid—carbonated soda ( soda + carbon dioxide) Liquid in Liquid—vinegar (water + acetic acid) Solid in Liquid—ocean water (water + sodium chloride)

Solid Liquid in Solid—dental amalgam (silver + mercury) Solid in Solid—steel (iron + carbon)

Solvation

The process of surrounding solute particles with solvent particles to form a solution This process in water is called hydration Attractive forces

solvent + solute > solute + solute

“like dissolves like” Based on polarity and bonding of particles as well as

intermolecular forces

Aqueous Solutions

Of ionic compounds

Of molecular compounds

Factors that Affect Rates of Solvation

Increased solvation if increased collision of particles Because solvation ONLY occurs when and where the

solute and solvent touch!

3 ways to increase collisions Agitating the mixture—stirring and shaking Increasing the surface area of the solute—breaking

solute into smaller pieces Increasing the temperature of the solvent

Heat of Solution

Overall energy change that occurs during the solution formation process

Energy required to overcome attraction within solute or solvent (endothermic)—feels cold

Energy released when solute and solvent particles mix (exothermic)---feels hot

Solubility

The MAXIUMUM amount of solute that will dissolve in a given amount of solvent at a specified temperature and pressure

Expressed in grams of solute per 100g of solvent

Unsaturated Solution Solvation > than recrystallization Contains LESS dissolved solute for a given temperature and

pressure than a saturated solution (more solute could still be added)

Saturated Solution Solvation = recrystallization Contains MAXIMUM amount of dissolved solute for a given

amount of solvent at a specific temperature and pressure

Factors that Affect Solubility

Pressure

The nature of the solute and solvent

Temperature Many (not all)

substances are MORE soluble at high temps, than low temps

Gas solutes in liquid solvents are LESS soluble at high temps fast gas particles

escape liquid faster when heated

Supersaturated Solutions

Contains MORE dissolved solute than a saturated solution at the same temperature. Formed at high temperatures Cooled slowly Ex Boiling water and adding lots of sugar

Unstable Stirring or tapping container = crystallization Ex. Rock Candy

Pressure

Affects solubility of gaseous solutes Pressure Solubility

Explains how we make carbonated soda pressure to solubility of carbon dioxide

(supersaturated) Cap the soda = trapped carbon dioxide in bottle Uncap the soda = carbon dioxide can escape

Henry’s Law

Explains the decreased solubility of the carbon dioxide contained in the soda after the cap is removed

At a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid S = g/L P = varies

Solution Concentration

I will state the concentrations of solutions in different ways

I will calculate the concentrations of solutions

Solution Concentration

A measure of how much solute is dissolved ins specific amount of solvent or solution.

May be used as a qualitative description Concentrated- contains a large amount of solute Diluted- contains a small amount of solute

Expressing Concentration

May be used as a quantitative description Percent by mass Percent by volume Molarity Molality

Express concentration as a ratio of measured amounts of solute and solvent or solution

Concentration Ratios

Concentration Ratios

Concentration Description Ratio

Percent by Mass

Percent by Volume

Molarity

Dilutions

Molality

Percent by Mass

Percent by Volume

Molarity (M)

Molar Concentration M = Molar Examples:

1M solution = A liter of solution containing one mole of solute 0.1M solution = A liter of solution containing 0.1 mole of solute

MUST know Volume of the solution Amount of dissolved solute

1𝐿=1000𝑚𝐿

Molarity (M)

Diluting a Solution

Diluting a Solution

Diluting a Solution

Colligative Properties of Solutions

I will explain the nature of colligative properties

I will describe four colligative properties of solutions

I will calculate the boiling point elevation and the freezing point depression of a solution

Molality (m)

Temperature causes volume of a solution to change, causing Molarity to change.

To prevent running into that problem, scientists sometimes uses Molality instead since that doesn’t change with temperature.

1𝑘𝑔=1000𝑔

Molality (m)

Colligative Properties

Physical properties of solutions that are affected by the number of particles but NOT the identity of dissolved solute particles “depending on the collection”

Example: Vapor pressure lowering Boiling point elevation Freezing point depression Osmotic pressure (NOT on test)

Electrolytes

Ionic compounds (some molecular compounds) Dissociate in water Conduct an electric current

Strong Produce many ions in solution Ex NaCl(s) Na+(aq) + Cl-(aq)

1 mole NaCl (aq) = 1 mole Na ions + 1mole Cl ions 1 mole NaCl (aq) = 2 moles solute particles in solution

Weak Produce only a few ions in solution

Nonelectrolytes

Many molecular compounds Dissolve in solvents Do NOT ionize (do NOT dissociate

when dissolved….stay as one particle) Do NOT conduct electric current

Example Sucrose 1m sucrose solution = 1 mole sucrose

particles

Vapor Pressure Lowering

Vapor pressure The pressure exerted in a closed container by liquid

particles that have escaped the liquid’s surface and entered the gaseous state

LOWERS due to the number of nonvolatile solute particles in solution Solute particles occupy some surface area Solvent particles have less surface area to escape to a

gaseous state

Nonvolatile solute One that has little tendency to become a gas

Predicting Effect of Solute on Vapor Pressure

Based on electrolyte or nonelectrolyte

Examples 1 mole nonelectrolytes = same relative effect on Vp

Glucose1mole Sucrose1mole Ethanol 1mole

1 mole electrolytes = increasingly greater affect on Vp Sodium chloride (NaCl) 1 mole Na+ 1mole Cl-

Sodium sulfate (Na2SO4) 2 mole Na+ 1 mole SO4-

Aluminum Chloride (AlCl3) 1 mole Al+ 3 mole Cl-

Boiling Point Elevation

Boiling vapor pressure = atmospheric pressure

What happens when a nonvolatile solute is dissolved in a solvent? At normal boiling point, vapor pressure is still LESS than

atmospheric pressure Must be heated to raise vapor pressure

Boiling point elevation The temperature difference between a solution’s boiling point and

pure solvent’s boiling point The greater the number of solute particles in the solution, the

greater the boiling point elevation

Freezing Point Depression

Freezing Point Temperature (solvent) Particles NO longer have sufficient kinetic energy to overcome

the interparticle attractive forces The particles form into a more organized structure (solid)

What happens when a solute is dissolved in a solvent? Solute interferes with attractive forces among solvent particles PREVENTS solvent from entering solid state at normal freezing

point Freezing points of solutions are always LOWER than that of the

pure solvent

Freezing Point Depression The difference in temperature between its freezing point and the

freezing point of its pure solvent

Calculate Solution Boiling/Freezing Point

Pure Solute vs Solution

Osmosis and Osmotic Pressure

Osmosis the diffusion of solvent particles across a semipermeable membrane Higher solvent concentration Lower solvent concentration EX. Kidney dialysis or uptake of nutrients by plants

Semipermeable membranes Barriers with tiny pores Allow some (NOT all) kinds of particles to cross Ex. Surrounding ALL living cells

Osmotic Pressure Amount of additional pressure caused by the water molecules that

moved into the solution Depends on # of solute particles in a given volume of solution

NOT ON TEST

Heterogeneous Mixtures

I will identify the properties of suspensions and colloids

I will describe different types of colloids

I will explain electrostatic forces in colloids

Heterogeneous Mixtures

Contain substances that exist in distinct phases Regions with uniform composition and properties

Different substances remain physically separate

Types Suspensions Colloids

Heterogeneous Mixtures

Example: Blood

The blood cells are physically separate from the blood plasma

The cells have different properties than the plasma.

The cells can be separated from the plasma by centrifuging physical change

Suspensions

A mixture containing particles that settle out if left undisturbed

Can be separated with a filter or by settling out

Suspended Particles Diameter > 1000 nm

Examples Cornstarch and water Sand and water Muddy water

Suspensions

Colloids

Heterogeneous mixture of intermediate size particles (between suspensions and solutions)

Can NOT separate with a filter or settling

Particles 1nm< diameter < 1000 nm

Example Homogenized Milk

Colloids

Brownian Motion

Erratic movement of colloid particles Dispersed particles make jerky, random movements Results from collisions of particles with dispersion

medium Prevents particles from settling out

Destroying a colloid (gives colliding particles enough energy to overcome electrostatic forces) Stirring in an electrolyte heating

Brownian Motion

Tyndall Effect

Particles are large enough to scatter light

Both concentrated & diluted colloids exhibit this effect Concentrated colloids look cloudy Diluted colloids may look clear

Suspensions also exhibit this effect

Solutions NEVER exhibit this effect

Tyndall Effect

The beam of light is visible in the colloid because of light scattering

Review