Chapter 3 Chemistry

Section 1: Working With Solutions There are two types of mixtures: 1) Solutions are well mixed mixtures. You

can’t separate them with filters, BUT you can boil the water away and it will leave it behind. Examples: Salt water, cool aid etc.

2) Suspensions are mixtures that contain particles that can be seen and separated by a filter. Examples: Muddy water, paint, flour and water, blood

A Closer Look at Suspensions

A Closer Look at Solutions

Solutions are made of two parts1) Solvents: That which dissolves a

substance.2) Solutes: A substance that is

dissolved in a solvent and is present in a smaller amount.

Water: The Universal Solvent

Why is water called the “universal solvent?”

It dissolves a lot of substances…not all, but a whole bunch! Thirsty?

Solutions Without Water

Gasoline: A solution of different fuels. Several hydrocarbons and ethanol (Biofuel.)

Brass: A solution of zinc and copper Air: A solution of Nitrogen, Oxygen

and other gases.

Concentration

Two different concentrations:1) Dilute Solutions: A little solute is

dissolved in a solvent.2) Concentrated Solution: Solutions

with a lot of solute dissolved in a solvent.

Solubility

A measure of how well a solute can dissolve in a solvent at a given temperature.

A saturated solution is holding the maximum amount of solute it can. Add more and it will settle to the bottom of the solvent.

An unsaturated solution can hold more solute to bring it up to saturation.

Sponge Example!

Temperature can affect solubility!

You can dissolve more solutes (like Cool aid) in warm water than you can in cold. It dissolves faster too!

Example: Mr.Lynch’s Coolata!

Let’s Graph Solubility!

Data: Temp(oC) Solubility (g/100g of

H2O) 0 13 20 31 40 65 60 108 80 164 100 247

Set up your graph

1) Determine what goes on the x and y axis. Do this by asking yourself , does solubility affect temperature or does temperature affect solubility . The one that affects the other is the X axis variable. (A.K.A. independent variable.) The Y variable is the other. (A.K.A. dependent variable.)

2) Choose number scales that cover all of your values. Use a continuous increment.

What are Continuous Increments?

Continuous increment means going with the same increase each time. Example: 0,2,4,6,8 (2 is the increment) or 0,3,6,9,12 (3 is the increment)

Graphs aren’t worth the paper they’re printed on without continuous increments!

Graph Reminders

Y

X

20 4

0

2

5HUH?

Let’s Graph Solubility!

Data: Temp(oC) Solubility (g/100g of

H2O) 0 13 20 31 40 65 60 108 80 164 100 247

Effects of Solutes on Solutions

Lower Freezing Points:Adding solute to solvents will lower the freezing temperatures of the solutionExample: Water will freeze at a lower temperature when the solute salt is dissolved in it. That’s why we use it on roads in the winter time! The ice will form at lower temperatures.

Higher Boiling Points:The addition of a solute to a solvent will increase the boiling temperature of the solution. Example: We add salt to boiling water to make it boil at a higher temperature. It cooks the food faster!

Describing Acids and Bases

Acids:-Produce H+ ions in water-Taste sour (Don’t try this at home!)-React with metals and carbonates-Turn blue litmus paper redExamples:

Bases: -Produce OH- ions in water -Taste Bitter (DON’T) -Feel slippery -Turns red litmus paper blue Examples:

Strengths of Acids and Bases

Strength of acids and bases means how well they break up into ions in water.

Ex: If you put an acid in water and it breaks up into a lot of H+ ions it’s a strong acid.A few H+ ions it’s a weak acid.Hydrochloric Acid is strongAcetic Acid is weak

If you put a base in water and it breaks up into a lot of OH- ions, it’s strong. A little, it’s weak.

Ex: Sodium Hydroxide is a strong base and Ammonia is a weak base.

Do not confuse strength with concentration!

A strong acid or base is still strong even if you dilute it with a lot of water. They still readily break up into ions but the damaging effects of the acids and bases will be reduced when they’re dilute.

The most dangerous acids and bases are concentrated strong acids and bases.

The pH Scale

-Helps us determine whether a solution is an acid or a base by measuring the concentration of H+ ions in solution

It’s a scale from 0-14 0-6 are acids. 0=strong, 6=weak 7 is a neutral solution. Neither acid

or base. 8-14 are bases. 8 is a weak base, 14

is a strong base.

Example of a pH Scale

Neutralization

The process of mixing an acid and a base in exact quantities to produce a neutral solution (pH of 7) made of water and salt.

If you don’t mix exact quantities the solution will still be either acidic or basic depending on which there was more of at the start.

Example of Neutralization

Acid + Base = salt and water Hydrochloric Acid + Lye Salt +

Water

HCl + NaOH NaCl + H2O