Environmental pH

(10 points)

Introduction:A liquid may be an acid, base, or neutral. The degree of acidity or basicity can be measured by using the pH scale. The scale is divided into three areas: Acid (readings below 7), neutral (reading of 7), and basic (readings above 7). Each division either increases or decreases the pH of a substance 10 times. The pH of 5 is ten times more acidic than a pH of 6. Water has a pH of 7 but when it mixes with air the suspended materials will either raise or lower its pH. Acid Rain is an example of this type of reaction. Acids: Acids are substances that produce hydrogen ions (H+) when dissolved in water. Ions can be positively or negatively charged particles, however in acids, they are positively charged, because the H+ ions have one more proton than electron. Acids taste sour. Lemons and tomatoes are both examples of acidic foods. Acids are corrosive and therefore have many important applications in household cleaners as well as in the human digestive system as they break down food. Acids also conduct electricity and therefore work well in car batteries. Bases: Bases are substances that produce hydroxide ions (OH-) when dissolved in water. Bases have a bitter taste, feel slippery, and can be corrosive. Baking soda and lye are examples of base materials. Most bases are oxides of metal. When an acid chemically bonds with a base, a salt usually forms.

Objective:The student will determine the pH of various substances and will also determine how some of these substances can affect the environment.

Materials:

  • pH paper and Chart
  • Forceps
  • Masking Tape
  • Micro testing tray
  • Various liquids

Procedure:

  • Label the micro testing tray wells.
  • Putfive drops of liquid in each well: Caution not to come in contact with any of the materials. If contact is made wash it off under running water and notify the instructor immediately.
  • Pick up a piece of pH paper with the forceps.
  • Hypothesize whether the liquid would be acid or base.
  • Record this on the data table below.
  • Touch the pH paper to the liquid in slide A and remove it. Compare the color of the paper with that on the pH chart.
  • Record your observation on the chart below.
  • Repeat the procedure with the rest of the wells.

Well / Hypothesis / ypH / Acidic / Basic / pNeutralp
A / d / d
B / d
C / D
D
E / s
F
G
H
I

Analysis:

1. Which of the liquids had the lowest pH ?

2. Which ofthe liquids had the highest pH?

3. Which of the liquids were closest to being neutral?

4. If the pH of a sample was 3 how many times more acidic is it than a solution with a pH of 6?

5. How might one correct the pH of a lake with a reading of 3?

6. What is the pH of human skin?

7. How does non-tearing shampoo work?

8. What is the pH of rain water?

9. What local industries pump materials into the atmosphere to create a drastic pH change in rain water?

10. Which solution contained the highest concentration of hydroxide ions (OH-)?

11. Which solution contained the highest concentration of hydrogen ions (H+)?

12. You have two solutions, one with a pH of 2 and the other with a pH of 6. Which one is the stronger acid and how much stronger is it?

13. You have two solutions, one with a pH of 11 and the other with a pH of 13. Which one is the stronger base and how much stronger is it?

Extension questions:

The diagram below is of a hypothetical food web found in an estuary.

Osprey

GeeseRatMinnow

Mole

SnailGrasshopper

Mosquito

Marsh Grasses, Sedges, and Algae

  1. Describe two abiotic factors of the aquatic component of this estuary that change twice daily.
  2. Draw an energy pyramid based on the food web. For each trophic level, give two examples of the organisms that would occupy that level.
  3. Cultural eutrophication can cause breakdowns in this type of food web. Give one example of how cultural eutrophication might occur and give one detrimental effect of this process.

Scientists designed an experiment to learn about the functioning of the hydrological cycle and the phosphorous cycle in a forest. Using two areas of the same size and geologic features, they cut all the trees down from one plot and did not disturb the other plot. They were able to accurately measure the amount of water that flowed out of the two plots as well as measure the amounts of phosphorous found in the runoff.

  1. Describe what the differences would be in the volume of water running off the two plots and give one reason why. Assume that the two areas received the same amount of precipitation.
  2. Describe the differences in the levels of phosphate found in the runoff of the two plots. Assume that both plots started off with the same amount of phosphorus in the soil.
  3. Describe one negative effect that might occur in a stream that receives the runoff water and sediment.
  4. When a tropical rain forest is cut down and used as farmland, the fertility of the soil only lasts a few years. Give an explanation as to why there is little organic matter in rain forest soil and what would happen to that material after deforestation.