Solutions. Chemistry Joke It’s a lit-moose test! What on earth does this have to do with chemistry?

SolutionsSolutions

Chemistry Joke

It’s a lit-moose test!

What on earth does this have to

do with chemistry?

SolutionsSolutions

Homogeneous MixturesHomogeneous Mixtures Uniform throughoutUniform throughout

Composed of a solute and a solventComposed of a solute and a solvent The The solutesolute is dissolved into the is dissolved into the solventsolvent The solute or the solvent can be a gas, a The solute or the solvent can be a gas, a

liquid, or a solid.liquid, or a solid.AirAir: gas / gas solution: gas / gas solutionSalt waterSalt water: solid / liquid solution: solid / liquid solutionCarbonated waterCarbonated water: gas / liquid solution: gas / liquid solutionSteelSteel: solid / solid solution: solid / solid solution

““Like Dissolves Like”Like Dissolves Like”

Polar solvents dissolve polar Polar solvents dissolve polar solutessolutes

Water is a polar molecule. It has an uneven distribution of charge.

Water will easily dissolve polar solutes such NaCl.

Nonpolar solvents dissolve Nonpolar solvents dissolve nonpolar solutesnonpolar solutes

““Like Dissolves Like”Like Dissolves Like”

Gasoline is a nonpolar molecule. It has an even distribution of charge.

Gasoline is often used as a solvent to clean nonpolar grease from machine parts.

Making SolutionsMaking Solutions In order to dissolve, the solvent In order to dissolve, the solvent

molecules must come molecules must come in contactin contact with with the solute.the solute.

Process is called Process is called solvation.solvation. 3 Factors3 Factors that affect the that affect the raterate

Stirring (agitation)Stirring (agitation) Particle size (surface area)Particle size (surface area) TemperatureTemperature

Making SolutionsMaking Solutions

1.1. StirringStirring moves fresh solvent into contact moves fresh solvent into contact with the solute.with the solute. It’s why we stir iced tea when we add It’s why we stir iced tea when we add

sugar.sugar.2.2. Smaller piecesSmaller pieces increase the amount of increase the amount of

surface area of the solute.surface area of the solute. Think of how fast a breath mint dissolves Think of how fast a breath mint dissolves

when you chew itwhen you chew it

Making SolutionsMaking Solutions3. Higher temperature makes the molecules of makes the molecules of

the solvent move around faster and contact the solvent move around faster and contact the solute harder and more often.the solute harder and more often.

Slowest Faster Fastest

Making SolutionsMaking Solutions

So, the rate of solubility is affected by:Stirring, Particle Size, & Temperature

What determines the amountamount of solute that will dissolve?Temperature & Pressure

Making SolutionsMaking Solutions

Temperature:Temperature: Affects the solubility of solids, liquids, and

gases. For most solids and liquids, the solubility

increases with increasing temps. For most gases, the solubility decreases with

increasing temps. As carbonated drinks get warm, they get “flat”

Effect of TemperatureEffect of Temperature

The mineral The mineral deposits around deposits around hot springs result hot springs result from the cooling from the cooling of the hot, of the hot, saturated solution saturated solution of minerals of minerals emerging from emerging from the spring.the spring.

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Effect of PressureEffect of Pressure

Pressure:Pressure: Affects only the solubility of gases.

Gas solubility increases as the partial pressure of the gas above the solution increases.

How Is Solubility Expressed?How Is Solubility Expressed?

Solubility Max amount of a substance that will dissolve at

a specific temp. Units are g solute/ 100 g solvent.

Saturated Contains the max amount of solute that can

dissolve Rate of particles dissolving equals rate of

particles crystalizing.

How Is Solubility Expressed?How Is Solubility Expressed?Unsaturated

Can still dissolve more solute Supersaturated

Holds more than it can theoretically contain

How Is Solubility Expressed?How Is Solubility Expressed?

Electrolytes Compounds that conduct electricity in

aqueous solution or in a molten state All ionic compounds are electrolytes Some ionic compounds are strong

electrolytes; others are weak electrolytes. Strong electrolytes dissociate (break apart)

completely. Weak electrolytes only partially dissociate.

Most molecular compounds do not conduct electricity. Called nonelectrolytes Sugar and rubbing alcohol are

nonelectrolytes

How Is Solubility How Is Solubility Expressed?Expressed?

NaCl: Strong Electrolyte

HgCl2: Weak Electrolyte

Glucose: NonElectrolyte

Colligative PropertiesColligative Properties Properties that affect solutions.Properties that affect solutions.

Depends only on theDepends only on the number of dissolved solute of dissolved solute particles—not on what particles—not on what kind of particle they are of particle they are

Two important colligative properties are:

1) Boiling point elevationAs solute particles are added to a solution, the boiling point rises.

2) Freezing point depressionAs solute particles are added to a solution, the freezing point lowers.

Ionic compounds work best because they dissociate in water into more particles.

In water, NaCl becomes Na+ and Cl-.

Chemistry Joke

Q: Why did the white bear dissolve in water?

A: Because it was polar!!