Introduction: Sketch the pH scale Solutions and pH Introduction: Sketch the pH scale

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

Water is the solvent of Life! 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 pH H2O  H+ + OH- One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-) Hydrogen Ion Hydroxide Ion Acid Base H2O  H+ + OH-

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

Acids and Bases Strength compared using pH scale Ranges from 0 – 14 Logarithmic Scale (gets 10x bigger/smaller) Acid – donates H+ when added to aqueous solutions Ranges from pH 0-6.9 Base – breaks up into hydroxide (OH-) ions and another compound when placed in an aqueous solution Ranges from pH 7.1 – 14 Distilled water is pH 7.0 or neutral. Why? H2O H+ + OH-

Acids:  Bases: Taste sour.  Taste bitter. Give sharp stinging pain in a cut or wound.  Feels slippery 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 pH of 1-3 Produce lots of H+ ions

Bases Strong Bases have a pH 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 pH (neutralization). Produced naturally by the body to maintain homeostasis Weak Acid Weak Base

Acids and Bases Buffers – compounds used to maintain a contant pH within a system H2CO3 H+ + HCO3- Carbonic acid bicarbonate ion

Acids and Bases

Making Biological Molecules and H2O Condensation Reaction H2O 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. 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 pH

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