Acids and Bases

Sour and Bitter

Acids: The term acid, in fact, comes from the Latin term acere, which means sour. Acids taste sour, are corrosive to metals, change litmus (a dye extracted from lichens) red, and become less acidic when mixed with bases. Bases: Bases (also known as alkalies) feel slippery, change litmus blue, and become less basic when mixed with acids.

Acids and Bases

Neutralization: (Acid) + (Base) = (Salt) + (Water)

HCl + NaOH = NaCl + H2O

Definitions of Acids and Bases

An acid is a substance that breaks into H+ ions in an aqueous solution.

A Base (alkaline) is a substance that breaks into OH− ions in an aqueous solution.

Note: aqueous solution is any solution where H2O is the solvent.

OH

Characteristics Of Acids

Acids can be characterized by:

1. A sour taste.

2. It turns blue litmus paper red

3. It tastes sour. Try drinking lemon juice (citric acid)

Characteristics of BasesA Base is characterized by:

1. A bitter taste. (Milk of Magnesia)

2. It feels slippery. (Soapy Water)

3. It turns Red Litmus Blue.

Where in the….S

What part of the tongue can taste a lemon or other sour things?

http://www.miamisci.org/ph/phplumber.html

Answer

The green areas are where you would taste sour foods such as a lemon.

Where in the….B

Where might you taste something bitter like baking soda?

Answer

The green area is where you would taste bitter foods such as baking soda.

This tells you how not to take those bitter pills.

Acid rain is rain that has been made acidic by certain pollutants in the air. Acid rain is a type of acid deposition, which can appear in many forms.

Wet deposition is rain, sleet, snow, or fog that has become more acidic than normal. Dry deposition is another form of acid deposition, and this is when gases and dust particles become acidic.

Both wet and dry deposition can be carried by the wind, sometimes for very long distances. Acid deposition in wet and dry forms falls on buildings, cars, and trees and can make lakes acidic. Acid deposition in dry form can be inhaled by people and can cause health problems in some people.

Acid Rain

Lifted from EPA website

What is the pH scale? The pH scale measures

how acidic or basic a solution is.

It ranges from 0-14.

7 is neutral.

A pH less than 7 is acidic. Lower pH, stronger Acid.

A pH of greater than 7 is basic. Higher pH, stronger base

pH stands for the “power of Hydrogen”

Lemon Juice 4

Baking Soda 8

Aspirin 5

Ammonia 10

Milk of Magnesia 8

Lava Soap 10

Borax 9

Water 7

Lemon Soap 6

Vinegar 4

Tonic Water 4

Liquid Plumber 12

Acid or Base?Weak or Strong?

http://www.miamisci.org/ph/phplumber.html

[H+] pH ExampleAcids 1 x 100 0 HCl  - Hydrochloric acid

1 x 10-1 1 Stomach acid1 x 10-2 2  Lemon juice1 x 10-3 3  Vinegar1 x 10-4 4 Soda1 x 10-5 5 Rainwater1 x 10-6 6 Milk

Neutral 1 x 10-7 7 Pure waterBases 1 x 10-8 8 Egg whites

1 x 10-9 9 Baking Soda1 x 10-10 10 Tums® antacid1 x 10-11 11 Ammonia1 x 10-12 12 Mineral Lime - Ca(OH)2

1 x 10-13 13  Drano®

1 x 10-14 14 NaOH

pH

-Table

Indicators

Indicators-- An indicator is a special type of compound that changes color as the pH of a solution changes, thus Gives us an approximate pH of the solution.

Many dyes (chemicals) are sensitive to hydrogen-ion concentration. Beyond a certain threshold, they change visible color and are used as indicators of the relative pH of a solution.

Litmus paper - Paper with powder extracted from certain plants that tests the pH of a substance. Acid turns red while base turns blue; neutral remains white.

Phenolphthalein

Phenolphthalein is a sensitive pH indicator with the formula C20H14O4. Often used in titrations, it turns from colorless in acidic solutions to pink in basic solutions, the color change occurring between pH 8 and pH 10. If the concentration of indicator is particularly strong, it can appear purple.

http://en.wikimedia.org/wiki/Phenophthalein

Phenolphthalein is insoluble in water, and is usually dissolved in alcohol for use in experiments.

It is a colorless, weak acid, which can lose H+ ions in solution. However, the phenolphthalein ion is pink. When a base is added to the phenolphthalein, the [atom ion] equilibrium shifts to the ionization because H+ ions are removed.

Make your own "litmus paper"1. Chop the red cabbage up with a sharp knife. 2. Crush it with a "pestle and mortar" OR put it

in a food mixer and grind it. 3. Add a very small amount of water. 4. Decant the blue liquid (pour the liquid into a

clean glass). 5. Soak some blotting paper in the blue liquid. 6. Let the blotting paper dry out. 7. Cut the blue papers into small squares.

When you buy the red cabbage it is actually blue. It will be quite blue when you slice it up and add some tap water. That is because your tap water is very slightly alkaline. If you add some vinegar it will turn red. This is because there is a pigment (coloured chemical) in the red cabbage which acts as a pH indicator.

http://www.sambal.co.uk/indicators.html

Why is acid an acid?

All substances are made up of millions of tiny atoms. These atoms form small groups called molecules. In water, for example, each molecule is made up of two hydrogen atoms and one oxygen atom. The formula for a molecule of water is H2O. "H" means hydrogen, "2" means 2 hydrogen atoms, and the "O" means oxygen.

Why continued

When an acid is poured into water, it gives up H (hydrogen) to the water. When a base is poured into water, it gives up OH (hydroxide) to the water.

Stronger acids give up more protons (the positively charged parts of atoms); stronger bases give up more OH- (hydroxide). Neutral substances have an even balance of protons and OH-.