A liquid may be an acid, base, or neutral. The pH scale can be used to measure how acidic or basic a solution is. The scale is divided into three areas: Acid (readings below 7), neutral (reading of 7), and basic (readings above 7). Each division either increase 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.
Students will determine the pH of various substances and their effect on organisms in the environment.
Wide range pH paper and chart, spot plate, forceps, soapy water, lemon juice, ammonia, cola, distilled water, pond water, salt water, baking soda solution, 8 dropper bottles.
- Using a spot plate, place a couple of drops of each solution into the numbered wells being careful NOT to mix solutions. (Well 1- soapy water, well 2- lemon juice, well 3- ammonia, well 4 – cola, well 5 – distilled water, well 6 – pond water, well 7 – baking soda solution, well 8 – vinegar))
- Pick up a piece of pH paper with forceps.
- Touch the pH paper to the liquid in well # 1 and remove it.
- Compare the color of the pH paper to the pH color chart.
- Record the pH on your data table.
- Use a new piece of pH paper each time, and repeat steps 2 – 5 for each of the other solutions.
1. Which liquid had the lowest ph?
2. Which of the liquids had the highest pH?
3. Which of the liquids was 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 someone correct the pH of a lake with a reading of 3?
6. What would be the pH of human blood?
7. How does non-tearing shampoo work?
8. What would be the likely pH of acid rain?
9. What industries in our area pump materials into the atmosphere to create a drastic change in rain water? (Hint: Some days you can smell this industry.)
10. List any substances that had a pH that would cause tadpoles & fish to die.