Acids, Bases and pH Image

Standards & Objectives  PWC Objective: Bio.2a  Critical Attributes: –Water can break into two charged ions (H+ and OH-) –The pH scale is used to rank how acidic or basic (alkaline) a solution is. –Organisms can only tolerate a small change in pH –Water has a pH of 7, but various substances added to it can change its pH  Essential Skills: -Understand the detrimental effects if the pH in a cell is changed considerably -Per volume, there are more H+ ions than OH- ions in an acidic solution; more OH- ions than H+ ions in a basic solution. 2

Water molecules can react to form ions H 2 O H + + OH - H + hydrogen ion OH - hydroxide ion

pH Scale -indicates the concentration (or #) of H+ (hydrogen ions) in a solution -Each step on the pH scale represents a factor of 10. -Ex. pH 4 has 10x more H+ than pH 5

pH Scale continued Range of pH is 0-14 More H+ ions = lower pH value More OH - ions = higher pH value (0 end of scale) (14 end of scale)

pH Scale

ACIDS Acidic solutions –Any substance that forms H+ ions in solution –pH lower than 7 (0-6 on pH scale)

Acidic substances SubstancepH Stomach acid1 Lemon juice2 Vinegar and soda3 Rainwater and shampoo5 Milk6

Let’s Practice! a.1.2 b.2.8 c.3.7 d.4.6 e.5.1 Which of the following would be considered the most acidic (strongest acid)? 1.2

Let’s Practice! a.1.2 b.2.8 c.3.7 d.4.6 e.5.1 Which of the following would be considered the least acidic (weakest acid)? 5.1

BASES Basic or alkaline solutions –Any substance that forms hydroxide (OH-) ions –pH higher than 7 (8-14 on pH scale)

Bases or Alkaline substances SubstancepH Egg8 Baking soda9 Antacid and soap10 Bleach13 Lye14 Image

Let’s Practice! a.8.1 b.10.4 c.11.7 d.12.9 e.13.8 Which of the following would be considered the least alkaline (weakest base)? 8.1

Let’s Practice! a.8.1 b.10.4 c.11.7 d.12.9 e.13.8 Which of the following would be considered the most alkaline (strongest base)? 13.8

NEUTRAL Neutral substances -The concentration of H+ and OH- ions are equal pH = 7 Ex. = pure water

Buffers BuffersBuffers –weak acids or bases that react with strong acids or bases and prevent sharp or sudden changes in pH

Buffers continued Without buffers in our body:Without buffers in our body: –Coma blood’s pH = 7.3 – 7.5 –Tetany blood’s pH increases to 7.8, muscles contract uncontrollably

Buffers, contd Without buffers in our body: –Acidosis – CO 2 builds up in blood and causes pH to decrease suddenly –Alkalosis – an uncorrected increase in blood pH

SALTS SaltsSalts = compounds that release ions other than H+ or OH- in solution –Salts and water are often formed when acids and bases mix

Let’s Review! a.1.1 b.4.9 c.9.1 d.11.5 e.13.9 Which of the following would be considered the most alkaline? 13.9

Let’s Review! a.1.1 b.3.4 c.8.2 d.10.6 e.13.9 Which of the following would be considered the most acidic? 1.1

Let’s Review! a.1.1 b.4.9 c.7.9 d.10.6 e.13.9 Which of the following would be considered the closest to neutral on this list? 7.9

Let’s warm up Based on the following chemical formulas identify the following as an acid or a base HCl Mg(OH) 2 H 2 SO 4 H 2 CO 3 KOH Ca(OH) 2 Draw and label a pH scale. |______________________|________________________| Place the following household items on the pH scale in the proper order: Baking soda9 Shampoo5 Bleach13 Vinegar2

How can you test the pH of items of items? Image Litmus Paper

Litmus PaperLitmus PaperLitmus PaperLitmus Paper Image Red stays red when an acid is present Red turns blue when a base is present Blue turns red when an acid is present Blue stays blue when a base is present

pHydrion paper Starts off golden yellow Use the guide to compare your paper to the known pH comparison paper.

Exploring the pH of common household items Using the litmus paper, let’s determine if it is an acid or a base? (record change/no change in blue and red litmus paper) pHydrion A paper unknownUsing the pHydrion A paper, determine the pH of the unknown in your test tube.

Exploring the pH of common household items DO NOT put the tweezers in the solution! Only the paper! Put the used papers IN THE BEAKER, NOT on your desk, paper, floor… BE CAREFUL! WASH YOUR HANDS IMMEDIALTEY!

Unknown Letter Red paper saw change? Blue paper saw change? Acid or Base? pHWhat you think it is: (Your prediction) Actual substance Example: Unknown ZYesNoBasePool chemicalsLye A B C D E F G H I J K L M N

Credits: Content: Bethzaida Vazquez Layout, animation, graphics: Amy Simcik Images and video clips: credit given throughout PowerPoint Corresponds with: Miller, K., & Levine, J. (2004). Biology. Upper Saddle River: Prentice Hall. Chapter 2-3.