Acids and Bases

 An acid is a compound that dissolves in water to form a solution with a pH lower than 7  A base is a compound that dissolves in water to form a solution with a pH greater than 7  The pH measurement indicates how acidic or basic a substance is  Recall that a pH is a measure of the number of hydrogen ions in a solution

Acid and Base Scale

Acids and Bases in your body  Acids and Bases are in the food we eat and the products we use  The are essential components of your biochemistry Example: Saliva is basic so our teeth won’t dissolve away Example: Saliva is basic so our teeth won’t dissolve away

Acids and Bases in your body  Your stomach makes hydrochloric acid which activates pepsin which works in the break down of proteins into amino acids  Sodium hydrogen-carbonate deactivate pepsin so it won’t eat away your intestines  NaHCO 3 then goes into your blood stream to act as a buffer  A buffer is a substance that can keep the pH of a solution nearly constant despite the addition of a small amount of acid or base

Properties of Acids and Bases  Your sense of taste helps you in sorting our acids and bases 4 forms of tastes are sweet, sour, salty and bitter 4 forms of tastes are sweet, sour, salty and bitter Latin word “acidus” means sour Latin word “acidus” means sour  Acids and bases feel different Bases are slippery such as soap Bases are slippery such as soap

Properties of Acids and Bases  Acids react with almost metals  Most bases do not react with metals  The easiest way to determine whether a substance is an acid or a bases is by determining its pH

Indicators  Acid-base indicators are chemicals that are used to determine if a solution is an acid or a base  Indicators change color depending on the pH of a solution  Litmus indicator is a chemical derived from lichen, a plant-like organism, or a werewolf  Litmus is usually used in paper format

Indicators  Blue litmus turns red when in an acid and in a base, it stays blue.  Red litmus stays red when in an acid and in a base it turns blue  In a neutral solution, such a pure water, litmus paper does not change color  Red = acid  Blue = base

Universal Indicator  A universal indicator is a mixture of several indicators that change color as the acidity changes

Universal Indicator

The pH scale  pH scale is a measure of acidity  Most solutions are between 0 and 14  A neutral solution has a pH of 7 at 25 o C  Acid substances are below a pH of 7  Bases have a pH higher than 7  Every increase of 1 on the pH scale indicates an increase of 10 in how basic a substance is  A decrease in 1 on the pH scale indicates a 10- times increase in acidity

Properties of Acids and Bases PropertyAcidBase TasteSourBitter Touch Not slippery Slippery Reaction with metals Metal corrodes, H2 bubbles form No reaction Litmus indicator RedBlue Electrical conductivity Conductive NOT Conductive pH of solution < 7 > 7