Module III - Ionic Phenomena PHYSICAL SCIENCE 416 MODULE III

ACIDS, BASES AND SALTS Objectives 2.1 To identify the properties normally used to classify substances in aqueous solutions as either acids, bases, or salts. 2.2 To determine the conditions under which substances will show the properties of acids, bases, or salts.

Substances BASES ACIDS SALTS

ACIDS = “acidus” (latin word) meaning sour. The word acids comes from one of its characteristic properties, its taste. ACIDS = “acidus” (latin word) meaning sour.

Bases BASES Bases are substances that are very slippery to touch and have a strong bitter taste.

Salts SALTS Salts are a source of ions that are easily absorbed by living organisms. They are often used to change the physical properties of various solutions by lowering the freezing points or raising the boiling points

Properties of Acids, Bases and Salts Electrical Conductivity Magnesium Taste/ Touch Litmus Paper ACID YES Reaction Sour Turns red BASE No Reaction Bitter/ Slippery Blue SALT Salty Depends on the solution Electrolytes – solutions that conduct electricity

(USED TO DETECT ACIDS OR BASES) INDICATORS (USED TO DETECT ACIDS OR BASES) Litmus paper is a type of indicator (thin strip of paper that is dipped into a solution) 2 Types: Blue Litmus Paper Red Litmus Paper ACIDS – Turn blue litmus paper red BASES – Turn red litmus paper blue BB

Indicators SALTS – not all salts are neutral - can be either acidic or basic (test with litmus paper)

Indicators INDICATORS Phenolphthalein is another type of indicator Bases turn clear phenolphthalein pink INDICATORS

NEUTRALIZATION ACID - BASE - “Making a solution chemically neutral” Chemically neutral – means does not contain an acid or base ACID - Neutralize it with a base BASE - Neutralize it with an acid Acids and bases neutralize each other forming a salt and water Ex. Acid + Base = Salt + water

REMEMBER... Acids, bases and salts conduct electricity Tap water will conduct (free ions around) Distilled water does not conduct (no free ions!)

Depends on the solution KEY POINTS Review chart: (very important!) Electrical Conductivity Magnesium Taste/ Touch Litmus Paper ACID YES Reaction Sour Turns red BASE No Reaction Bitter/ Slippery Blue SALT Salty Depends on the solution

PRACTICE PROBLEMS Worksheet # 1 Study guide, Module 3, page 2

References Science Quest, Grenier,Daigle & Rheaume, 1998 Physical Science Student Study Guide 416-436 Animation Factory Google Images