What is pH?

Acids and Bases Some of our favorite foods make our tongue curl up because they are SOUR.

Bitter! Some foods have a “bite” of their own because they’re somewhat bitter. WHY?

Acidic/Basic There is a scientific reason for this: These foods are either acidic or basic. Other substances besides foods have these characteristics.

Acids and Bases Chemicals may be classed as acids or bases. Things that are neither acids nor bases are neutral. pH measures how acidic or basic a solution is.

Acids Often taste sour Strong acids can burn skin & eyes Strong acids can dissolve metals Examples: Lemon juice Vinegar Car battery acid (dangerous!)

Bases Can taste bitter, sweetish, or salty Strong bases can burn skin & eyes Bases react more easily with protein than with metal; they are often used for cleaning Examples: Milk Baking soda Soap Drain cleaner (dangerous!)

Some substances are not really an acid or a base: For example, pure water

Most Substances: Can be identified as either acidic or basic Like the soil in our backyard.

pH Scale A scale that measures the acidity of a substance “p” stands for power and “H” stands for hydrogen;

The pH Scale pH scale ranges from 0 -14 pH 7 is neutral; neither acid nor base Pure water is pH 7 Low pH (0-6.9) = acid High pH (7.1-14) = base The closer to the ends of the scale, the stronger the solution is

How Do We Measure pH? We measure pH by using special strips of paper called pH paper

How Does It Work? The paper is treated with chemicals that change color to show the pH. When the paper touches the substance being tested, it turns a specific color to tell if the substance is an acid or a base.

The pH Scale

The pH Scale Each pH unit is 10 times as large as the previous one A change of 2 pH units means 100 times more basic or acidic x10 x100

Neutralization Reactions Neutralization reactions occur when an acid and a base react to form products that have a pH closer to 7, than the two reactants The reactants are an acid and a base The products are a salt (ionic compound) and water

Predicting products of Neutralization Reactions HCl (aq) + NaOH (aq)  H2O (l) + NaCl (aq) The sodium ion and the hydrogen ion switch places….forming NaCl and H-OH (water) This is a double displacement reaction!!

Predict the products of the following reactions and balance __ HNO3 + __ NaOH  __ HCl + __ Ca(OH)2  __ H2SO4 + __ LiOH  __ HNO3 + __ Ba(OH)2  __ HCH3COO + __ Al(OH)3 

Predict the products of the following reactions and balance 1 HNO3 + 1 NaOH  1NaNO3 + 1 H2O 2 HCl + 1Ca(OH)2  1 CaCl2 + 1 H2O 1 H2SO4 + 2 LiOH  1 Li2SO4 + 2 H2O 2 HNO3 + 1 Ba(OH)2  1 Ba(NO3)2 + 2H2O 3 HCH3COO + 1 Al(OH)3  1 Al(CH3COO)3 + 3 H2O

Homework Pg 275 # 2-5 Pg 281 # 2, 3, 5, 7 Chapter 7 review: Unit 1 Review pg 302-305 # 1-57

Other bases….. Some bases do not contain an OH and yet are basic! These include Metal oxides, eg. CaO, MgO Carbonates eg. CaCO3, (chalk) NaHCO3 (baking soda)