1. Learning Targets “I Can…” Interpret whether is a material is acidic, neutral, or basic using a pH sensor. Add an acid to a material and note the extent that it resists changes in pH Add a base to a material and note the extent that it resists changes in pH Compare the ability of different materials to resist pH changes

2. Acids and Bases How do we use pH Sensor to determine if a chemical is an acid or base?

3. Background Organisms are sensitive to the effects of acids and bases in their environment. Despite these changes, organisms need to maintain a stable internal pH to survive. Many biological, geological, and man-made chemicals are capable of stabilizing the environment’s pH, which allows organisms to survive better in the diverse environments of Earth.

4. Background Biological organisms (tissues or cells) Biological chemicalsNon-biological chemicals

5. What you will do today… Use a Labquest and pH probe to measure the pH level of a strong acid and a strong base Test various materials to compare their buffering ability, and thus their ability to help maintain homeostasis in a living organism

6. Table 1 Material TestedAdd pH, after adding this many drops 051015202530  pH Total Buffer Range acid base acid base acid base acid base acid base acid base acid base acid base acid base

7. Results DROPS pH

8. Results Table 2 MaterialInitial pHRank most acidic 2 3 4 5 6 7 8 least acidic

9. Chemicals As Buffers Buffers are chemicals, biological or otherwise, that resist changes in pH, thus maintaining homeostasis. To find the total buffer range of a chemical, subtract the ΔpH of acid from the ΔpH of base for each solution.

10. Results Table 3 MaterialBufferRank greatest change 2 3 4 5 6 7 8 least change

11. Conclusion Answer Questions 1-7 Due TUESDAY, 10/14!