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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
Acids and Bases
How do we use pH Sensor to determine if a chemical is an acid or
base?
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.
Background
Biological organisms (tissues or cells)
Biological chemicals Non-biological chemicals
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
Table 1
Material Tested Add
pH, after adding this many drops
0 5 10 15 20 25 30 DpH Total Buffer Range
acid
base
acid
base
acid
base
acid
base
acid
base
acid
base
acid
base
acid
base
acid
base
Results
DROPS
pH
ResultsTable 2
Material Initial pH Rank
most acidic
2
3
4
5
6
7
8
least acidic
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.
ResultsTable 3
Material Buffer Rank
greatest change
2
3
4
5
6
7
8
least change
Conclusion
• Answer Questions 1-7 • Due TUESDAY, 10/14!
