Physical ScienceChapter 22: Acids, Bases, and Salts

• Try to identify 2 common acids and bases which are commonly seen.

Acids• An acid is a substance which gives off H+

ions when it is mixed with water. Therefore, it always has hydrogen as part of it’s formula.

Properties of Acids

• All acids have certain distinctive properties.

These properties include:-pH value below 7-act as electrolytes (a liquid

which will conduct an electric current)

-are often poisonous

more

-acids taste sour

-are corrosive to metals and living

tissue

-turn litmus paper red

Different common acids

• Citric acid – found in lemons and limes

• Hydrochloric acid (HCl) – stomach acid

• Sulfuric acid

(H2SO4) – battery acid

• Acetic acid - vinegar

• Carbonic acid – carbonated beverages

• Nitric acid – TNT, nitroglycerin

• Phosphoric acid – detergents and fertilizers

• Acid rain is rain that has a lower than normal pH, making it more acidic.

This is caused by pollutants like sulfur and nitrogen compounds mixing and reacting with moisture in the air, to form compounds such as H2SO4, sulfuric acid.

Derrick noticed that at the old cemetery near his house, a lot of the headstones were weathered to the point where they could hardly be read. Derrick’s dad said that was due to the effects of acid rain.

“How could that happen here”, asked Derrick. “We live way out in the country.” Answer??

• Derrick then noticed that while a lot of the headstones were weathered to the point where they could hardly be read, others that were the same age were still very clear.

• What’s up with that?

Bases

• Bases produce OH- ions in a solution (water).

• Therefore, most bases have OH in their formulas.

• Some general properties of bases

include the following:

-pH greater than 7

-taste bitter

-slippery

-corrosive to metals and living tissue

-turn litmus paper blue

-act as an electrolyte

Some common bases

• NaOH (lye) – used in soaps and drain

cleaners

• NH3 (ammonia) – use in household

cleaners and fertilizers

• Aluminum hydroxide - deodorants

• Magnesium hydroxide - laxatives and antacids

• Sodium bicarbonate – baking soda

pH

• The pH of a solution tells how basic or acidic it is. 0-14

• A pH of 7 is completely neutral, and the strength of the acid or base increases the further away it is from 7.

• Acids and bases will neutralize each other. Neutralization is a chemical reaction where the properties of an acid and a base will cancel each other out.

• Ex. Vinegar and baking soda

• An indicator is a material which will produce predictable color change when exposed to an acid or a base.

Litmus paper is a particular type of indicator which turns red in an acid and blue in a base.

Salts• A salt is a compound which forms

when the negative ion from an acid combines with the positive ion from a base.

For example: NaOH + HCl NaCl + H20

The NaCl is a salt, Na+ and Cl-

Soap• A soap is an

organic salt, meaning a salt with carbon in it's formula.

• Most solid soap will have NaOH in it, while most liquid soap will have KOH.

• The process of soap-making is called saponification.

+

animal fat ashes soap

(tallow) (lye)

Detergents

• A detergent is a special type of soap which does not produce a soap scum in hard water.

• A hydrate is a compound with water chemically attached, and part of it’s formula.

• Ex.: concrete, plaster of paris, sodium

polyacrylate

The End