1. Acids and Bases Ch. 2 Pre-AP Biology Ms. Haut

2. Despite strong bonds in water molecules, a portion of bonds break, forming a H + and OH - Despite strong bonds in water molecules, a portion of bonds break, forming a H + and OH - H 2 0  H + + OH - H 2 0  H + + OH - A compound that releases H + ions in solution is an acid, and one that accepts H + ions in solution is a base A compound that releases H + ions in solution is an acid, and one that accepts H + ions in solution is a base Acidity is measured on the pH scale: Acidity is measured on the pH scale: –0-6.9 is acidic –7.1-14 is basic –Pure water and solutions that are neither basic nor acidic are neutral, with a pH of 7 2.15 The chemistry of life is sensitive to acidic and basic conditions

3. The pH scale The pH scale Each pH unit represents a tenfold change in concentration of H+ Figure 2.15 pH scale Acidic solution Neutral solution Basic solution Increasingly ACIDIC (Higher concentration of H + ) Increasingly BASIC (Lower concentration of H + ) NEUTRAL [H + ] = [OH – ] Lemon juice; gastric juice Grapefruit juice Tomato juice Urine PURE WATER Seawater Milk of magnesia Household ammonia Household bleach Oven cleaner Human blood H+H+ OH –

4. pH Indicators: Cabbage Juice Boiled cabbage creates a bluish juice that can be used to test pH of substances Boiled cabbage creates a bluish juice that can be used to test pH of substances http://pbskids.org/zoom/activities/sci/cabbageju iceindicato.html

5. pH Indicators Cabbage juice responds like litmus paper Cabbage juice responds like litmus paper –Indicator turns:  Red in Acids  Blue in Bases http://www.uni- regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusc h/Grafik/cabbage.gif http://www.howe.k12.ok.us/~jimaskew/litmus.jpg

6. pH Indicators Other indicators: Other indicators: –pH paper – phenolphthalein -turns pink in -turns pink in presence of base presence of base http://www.bio-world.com/images/061036.jpg http://ull.chemistry.uakron.edu/organic_l ab/distribution/dist13.gif

7. Cells are kept close to pH 7 by buffers Cells are kept close to pH 7 by buffers Biological fluids contain buffers to maintain a stable pH Biological fluids contain buffers to maintain a stable pH – pH of blood is 7.4 –Outside of a narrow range, enzymes denature & reactions stop (That’s a bad thing!) Buffers are substances that resist pH change Buffers are substances that resist pH change They accept H + ions when they are in excess and donate H + ions when they are depleted They accept H + ions when they are in excess and donate H + ions when they are depleted –Buffers are not foolproof

8. Some ecosystems are threatened by acid precipitation Some ecosystems are threatened by acid precipitation Acid precipitation is formed when air pollutants from burning fossil fuels combine with water vapor in the air to form sulfuric and nitric acids Acid precipitation is formed when air pollutants from burning fossil fuels combine with water vapor in the air to form sulfuric and nitric acids 2.16 Connection: Acid precipitation threatens the environment Figure 2.16A

9. –These acids can kill fish, damage buildings, and injure trees –Regulations, new technology, and energy conservation may help us reduce acid precipitation Figure 2.16B

10. In a chemical reaction: In a chemical reaction: –reactants interact –atoms rearrange –products result 2.17 Chemical reactions rearrange matter REARRANGEMENTS OF ATOMS 2 H 2 +O2O2  2 H 2 O Figure 2.17A

11. –Living cells carry out thousands of chemical reactions that rearrange matter in significant ways Figure 2.17B Beta-caroteneVitamin A (2 molecules)

12. Acknowledgements Unless otherwise noted, illustrations are credited to Pearson Education have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher. Unless otherwise noted, illustrations are credited to Pearson Education have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.