Describing Acids and Bases Acids & Bases in Solution Chapter 7, Section 3 & 4 Describing Acids and Bases Acids & Bases in Solution

Properties of Acids Taste sour React with metals and carbonates Turn blue litmus paper red Some common acids: Hydrochloric acid Nitric acid Sulfuric acid Carbonic acid Acetic acid Table Talk: Can you think of some other foods that are acidic based on their sour taste? DO NOT RANDOMLY TASTE CHEMICALS!

Acids React With Metals Acids React With Carbonates Acids react with magnesium, zinc, and iron to produce hydrogen gas Corrosive = they wear away other materials Carbonate ion = CO32- CO2 gas is formed Hydrochloric acid on limestone

Acids React With Indicators How Acids are Commonly Used Litmus paper, made from a dye found in lichens, turns red in an acid, blue in a base Many of the vitamins in foods you eat are acids Ascorbic acid = vitamin C Folic acid is in leafy green vegetables Nitric acid and phosphoric acid are used to make fertilizers Sulfuric acid is in batteries Muriatic acid helps clean swimming pools

Table Talk: summarize the properties and uses of acids

Properties of Bases Common Uses of Bases Taste bitter Feel slippery Turn red litmus paper blue Some common bases: Sodium hydroxide Calcium hydroxide Ammonia In cement Cleaning solutions In baking (baking soda)

Solutions Solution = A uniform mixture that contains a solvent and a solute Solvent = the part of the solution present in the largest amount; it dissolves the other substance Solute = the substance that is present in a solution in the smaller amount; it gets dissolved by the solvent

Acids in Solution Bases in Solution Acids in water solution separate into hydrogen ions (H+) and negative ions Example: HCl  H+ + Cl- Most bases are made of positive ions combined with hydroxide ions When bases dissolve in water, the positive ions and the hyroxide ions separate NH3 + H2O NH4+ + OH-

Strength of Acids & Bases “Strength” refers to how well an acid or base produces ions in water Knowing the concentration of hydrogen ions is the key to knowing how acidic or basic a solution is This is measured with the pH scale, a range of values from 0-14, with 7 being “neutral” (neither acidic or basic) The lower the pH, the more concentrated the ions are and the more acidic the solution is. See BrainPop “pH Scale”

Table Talk: If you found that certain foods upset your stomach or gave you heartburn, what could you say about them? How could you ease that uncomfortable feeling?

Acid-Base Reactions Neutralization = a reaction between an acid and a base Example: HCl + NaOH  H2O + Na+ + Cl- After neutralization, a acid-base mixture is less acidic or basic than either of the individual starting solutions This do-it-yourself volcano is actually an acid-base reaction between vinegar (an acid) and baking soda (a base). The foaming is the formation of CO2 gas.

Products of Acid-Base Reactions To a chemist, salt = an ionic compound that can be made from the neutralization of an acid and a base In a neutralization reaction, an acid reacts with a base to produce a salt and water: HNO3 + KOH  H2O + K+ + NO3- Table Talk: Potassium nitrate, KNO3, is a salt. Why is it split apart into ions in this equation? Answer: because potassium nitrate is soluble in water. What do you think would form if a salt was insoluble in water? A precipitate! See BrainPop “Acids & Bases” & “pH Scale” end