Solutions and p H Introduction Sketch the p

Solutions and p. H Introduction: Sketch the p. H scale

Solutions & Suspensions • Water is usually part of a mixture. • There are two types of mixtures: – Solutions – Suspensions

Properties of Water Universal Solvent Water is the solvent of Life! Solute – substance dissolved in a solvent to form a solution Solvent – fluid that dissolves solutes Example: Ice Tea – water is the solvent and tea and sugar the solutes

Solution • Ionic compounds disperse as ions in water • Evenly distributed • SOLUTE – Substance that is being dissolved • SOLVENT – Substance into which the solute dissolves

Solution

Suspensions • Substances that don’t dissolve but separate into tiny pieces. • Water keeps the pieces suspended so they don’t settle out.

Acids, Bases and p. H One water naturally Ion (H+) molecule in 550 million dissociates into a Hydrogen and a Hydroxide Ion (OH-) H 2 O Hydrogen Ion Acid H+ + OH - Hydroxide Ion Base

The p. H Scale • Indicates the concentration of H+ ions • Ranges from 0 – 14 • p. H of 7 is neutral • p. H 0 up to 7 is acid … H+ • p. H above 7 – 14 is basic… OHb • Each p. H unit represents a factor of 10 X change in concentration • p. H 3 is 10 x 10 (1000) stronger than a p. H of 6

Acids and Bases Strength compared using p. H scale Ranges from 0 – 14 Logarithmic Scale (gets 10 x bigger/smaller) Acid – donates H+ when added to aqueous solutions Ranges from p. H 0 -6. 9 Base – breaks up into hydroxide (OH-) ions and another compound when placed in an aqueous solution Ranges from p. H 7. 1 – 14 Distilled water is p. H 7. 0 or neutral. Why? H 2 O H+ + OH-

Acids: Bases: Taste sour. Taste bitter. Give sharp stinging pain in a cut or Feels slippery wound. Turn blue litmus paper red. Turn red litmus paper blue. Turn phenolphthalein colorless. Turn phenolphthalein pink. React with metals to produce hydrogen gas. React with carbonates or bicarbonates to produce carbon dioxide gas.

Acids • Strong Acids have a p. H of 1 -3 • Produce lots of H+ ions

Bases • Strong Bases have a p. H of 11 to 14 • Contain lots of OH-ions and fewer H+ ions

Buffers • Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in p. H (neutralization). • Produced naturally by the body to maintain homeostasis Weak Acid Weak Base

Acids and Bases Buffers – compounds used to maintain a contant p. H within a system H 2 CO 3 Carbonic acid H+ + HCO 3 - bicarbonate ion

Acids and Bases

Making Biological Molecules and H 2 O Condensation Reaction H 2 O Hydrolysis Reaction

Practice When most people think of chemistry the first terms that come to mind are acids and bases. Many of the chemicals that people run across have some connection to acids and bases. For instance many people take medicine every day to cure heart burn. These medicines are (acids/bases). One of these comes in a blue bottle and is known as “Dr. MOM”. The common name for this is Milk Of Magnesia Another product claims that it is better for us to use because it contains calcium. So in addition to helping relieve the heartburn, it also provides us with needed calcium. This product is called Tums and its chemical name is _________.

Practice Another product that is used all the time is Draino is a(n) (acid/base) and it has the common name of “lye” the chemical name is ___________, and the chemical formula is __________. This chemical is more dangerous than the ones used for heartburn and can cause blindness or burns. (Acids/Bases) are also commonly used to produce soaps and have a (bitter/sour) taste.

Practice Seltzer water and all sodas contain a very mild (acid/base) known as ___________. This is formed by dissolving carbon dioxide in water. The chemical formula for this substance is __________. Vinegar is a(n) (acid/base) finds its way into our diet in ketchup and most salad dressings. The chemical name for vinegar is , the chemical formula for this substance is __________.

Homework • Keep track of what you eat today and determine which are acids and bases • Bring things in from home that you would like to test for p. H

Application • Why is it important to know about p. H in Biology? • What happens to p. H of solutions in your body when you don’t drink enough? • What happens to p. H of solutions in your body when you eat to many sour foods?