MixturesWater

pH

Honors Biology

Mixture:A combination of two or more

substances that are physically mixed

They are not chemically combined!!Examples: soil, salsa, trail mix, milk &

cereal, sugar water.

Types of Mixtures:

A. Solution: A mixture formed when one substance dissolves in another- molecules are evenly distributed.

1. Solute: the substance that is dissolved in a solution

2. Solvent: the substance that does the dissolving.

Example: salt water

solute=salt, solvent=water

Parts of a Solution :

1. Solute: the substance that is dissolved in a solution

2. Solvent: the substance that does the dissolving.

Parts of a Solution :

B. Suspension: Mixture of water and non-dissolved materials

(In between a Mixture and Solution)A Colloid: A suspension where you can’t see

materials with naked eye

Examples: Blood, Milk

Now test what you learned:

Indicate whether each is a mixture, solution or suspension.

Unknown #1: Mixture

Salt & Pepper

Unknown #2:

Saltwater: Solution

Solute:

Solvent:

Water

Salt

Unknown #3:

Solution

Solute:

Solvent:

Sugar

Lemon Juice

Unknown #4:

SuspensionMuddy Water

Unknown #5:

Solution

Solute:

Solvent:

Chocolate

Milk

Unknown #6:

Solution

Solute:

Solvent:

Kool-Aid

Water

Kool-Aid

Special Type of SolutionEmulsion – a type of Colloid

An emulsion is a suspension of two liquids that usually do not mix together.

For example if we mix oil and water a suspension will form that over time separates. But now, if we add a few drops of a third substance, the emulsifier, and shake the mixture the oil and water will stay mixed much longer.

Examples of emulsions include butter and margarine, and mayonnaise.

Water: Needed for Life

Water has several properties that make it necessary for life.

It is POLAR - It has area with a slight positive charge, and an area with a slight negative charge.

Water: Needed for Life

This polarity gives us the property of Hydrogen Bonding.

Water: Needed for Life

Hydrogen Bonding allows one water molecule to “stick” to another water molecule.

Water: CohesionCohesion is the ability for water molecules

to stick to themselves

Beads of WaterSurface Tension

Water: Adhesion

Adhesion is the ability for water molecules to stick to other materials

Meniscus in a graduated cylinder

Water: A Great Solvent

Remember… A solvent has the ability to

dissolve other materials

Water is a solvent for many things

For example: The liquid part of your blood (the plasma) is 90% water

Some items, such as fats and oils DO NOT dissolve in water.

pH: What is it?

The pH scale is used to measure the strength of acids and bases

pH: What is it?

Some compounds break up into ions when they dissolve in water.

Solutions with more H+ ions are more ACIDIC They have a LOW pH (<7)

Solutions with less H+ ions are more BASIC They have a HIGH pH (>7)

H2O H+ + OH-

pH: What is it?

Some properties of acids and bases

pH Example Characteristics

Acids

Neutral

Bases

< 7

= 7

> 7

Lemon vinegar soda, aspirin

Sour, burns, dissolves things

Pure Water ------

Soap,baking soda, ammonia

Bitter, Slippery

pH: Looking at common items

Battery Acid

pH = 0

Orange Juice

pH = 3

Ocean Water

pH = 8

Oven Cleaner

pH = 13

pH: Importance to Humans

Blood has a pH of 7.4 (about neutral)

If pH goes below 6.8 or above 7.8 it is deadly!

To keep blood at the proper pH - our body uses buffers

pH: Buffers

Buffers are weak acids or bases that neutralize, or weaken, strong acids or bases.

In blood, buffers prevent pH change.

Sodium bicarbonate, or baking soda, is a buffer