I cannot do all the good that the world needs, but the world needs all the good that I can do. Jana
Idea Transcript
pH: Acids and Bases
pH Scale ▪ pH = potential of Hydrogen ▪ Measures how acidic (more H+) or how basic/alkaline (more OH-) a solution is H+ + OH- H2O acid + base neutral
Oven cleaner Toothpaste Human Blood Pepto Bismol Windex Baking Soda
How is pH regulated in our bodies? • Through buffers-> compounds that can bind to H+ ions when the H+ concentration increases, and can release an H+ ion when the H+ ion concentration decreases. • Example-> normal pH of blood is 7.35-7.45 (slightly basic). Any small change could disrupt cells and could potentially be fatal.
1. A student mixes strawberry Kool-Aid and water. The pH was taken using an indicator; the pH was 5.4. What kind of solution is strawberry KoolAid? ________________ 2. In the Kool-Aid mixture, what must there be more of, hydrogen ions or hydroxide ions? ___________________ 3. A student adds an Alka-Seltzer tablet to the Kool-Aid and stirs. The pH is now 8.3. What was released by the Alka-Seltzer tablet to cause this change? _________________________ 4. Bromothymol blue is a chemical indicator that turns blue in basic and neutral solutions, and turns greenish and then yellow as the solution becomes increasingly acidic. Fill in what color you think bromothymol blue would be in each of the situations in the chart. Situation
Ph
Water directly out of tap
pH =7.2
pH after exhaled air is blown through a straw into water for 5 min.
pH=5.1
pH after a snail has lived in water for three day
pH=5.8
pH with 2mL of bleach added to the water
pH=9.4
pH with instant coffee added to the water
pH=5.0
pH after an aquatic plant is grown in water for three days in bright sunlight
pH=7.7
Indicator Color
Chemical Reactions
Reactants – Substances changed by chemical reaction
The amount of energy needed to break a chemical bond or the energy released when a bond is broken.
Direction of reaction
Products – Substances formed by chemical reaction
When reactants and products are formed at the same rate.
Activation energy
6. Amount of energy released
Products
Reactants
Activation energy
10. Amount of energy absorbed
Reactants
Products
Exothermic • Chemical reaction releases more energy than it absorbs. • Ex: Cellular Respiration
Endothermic • Chemical reaction absorbs more energy than it releases. • Ex: Photosynthesis
Meanings…… • C6H12O6 = Glucose • H2O= Water • O2 = Oxygen • CO2 = Carbon Dioxide
Photosynthesis vs. Cellular Respiration
6CO2 6 H 2O C6 H12O6 6O2 light
C6 H12O6 6O2 6CO2 6 H 2O 36 ATP
Relationship • The products of photosynthesis are the reactants of cellular respiration. • It’s a continuous cycle.