ACIDS, BASES, AND THE PH SCALE GRADE 7 SCIENCE
Objective: Mississippi College- and Career-Readiness Standards for Science (2018) 7.5D.3 Collect, organize, and interpret data using various tools (e.g., litmus paper, pH paper, cabbage juice) regarding neutralization of acids and bases using common substances. Mississippi Science Framework 2010 2b. Categorize types of chemical changes, including synthesis and decomposition reactions, and classify acids and bases using the pH scale and indicators. (DOK 2)
VOCABULARY TERMS Acids Bases pH Neutralization
WHAT IS AN ACID? Any compound that increases the number of Hydronium ions (H+) when dissolved in water. Ranges from 0 to 6.9 on the pH scale The more H + ions, the more acidic the solution.
PROPERTIES OF ACIDS Tastes Sour Conduct Electricity Corrosive-can corrode fabric, skin, and paper Some acids react strongly with metals May be poisonous
USES OF ACIDS Acetic Acid = Vinegar Citric Acid = lemons, limes, oranges, and sour candies Ascorbic acid = Vitamin C which your body needs to function. Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics. Car batteries
WHAT IS A BASE? Any compound that increases the number of Hydroxide ions (OH-) when dissolved in water. Ranges from 7.1 to 14 on the pH scale
PROPERTIES OF BASES Feel Slippery Taste Bitter May be corrosive Can conduct electricity. Do not react with metals. May be poisonous.
USES OF BASES Soaps, ammonia, oven cleaner, and many other cleaning products Chalk Your blood is a basic solution.
WHAT ARE NEUTRAL SOLUTIONS? Solutions that are neither acidic or basic Contain equal concentrations of hydrogen and hydroxide ions. Have a pH of 7
NEUTRALIZATION A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.
ACID – BASE REACTIONS
Each salt listed in this table can be formed by the reaction between an acid and a base.
PH SCALE pH – measure of the Hydronium ion (H+) concentration in a solution. The pH scale ranges from 0 to 14.
PH SCALE Acidic solutions have pH values below 7. acids Acidic solutions have pH values below 7. A solution with a pH of 0 is very acidic with a high H+ concentration.
PH SCALE A solution with a pH of 7 is neutral. Neither acidic nor basic. Equal concentrations of H+ and OH-.
PH SCALE Basic solutions have pH values above 7. bases Basic solutions have pH values above 7. A solution with a pH of 14 is very basic with a low H+ concentration.
PH SCALE A change of 1 pH unit represents a tenfold change in the acidity of the solution. Example: Solution A pH = 1 Solution B pH = 2 Solution A is ten times more acidic than Solution B.
HOW TO DETERMINE WHETHER SOLUTIONS ARE ACIDIC OR BASIC. Method # 1-Look at the chemical formula H= acid OH = Base _____ HCL ____ NaOH ____ HBr ____KOH
METHOD #2 -INDICATORS Substance that changes color in the presence of an acid or base. Types of indicators: Litmus paper 2.
LITMUS PAPER Litmus paper-a strip of paper used to determine whether a solution is an acid or base. Base Turns red litmus paper blue Blue litmus paper remains blue Acid Turns blue litmus paper red Red litmus paper remains red Neutral red and blue paper does not change color