Purpose: The purpose of this lab was to measure the effects of acids and bases on biological and non-biological materials- more specifically, we were testing how capable each substance was at resisting pH changes with the addition of an acid or base.
Introduction: Every substance has a pH and the levels vary due to amount of hydrogen and hydroxide. Acids have more hydrogen than bases do. Bases have more hydroxide than the acids. Acids donate hydrogen and therefore make the substance more acidic. Some substances resist the change to acids and bases more than others.
Method:
For this experiment we used Logger Pro 2 (for data collection), two beakers (one labeled acidic and the other basic), two pH probes, water, buffered aspirin, orange juice, acid, base, and dropper.
20mL of water was measured out and poured into each beaker. Once prepared, the pH probes were placed into the beakers (one per beaker). Using a dropper, 30 drops of acid were put into the beaker labeled "acid" and 30 drops of base were put into the beaker labeled "base". Data was collected after every 5 drops.
Once that was completed, the beakers and probes were rinsed and the procedure was repeated for buffered aspirin and orange juice.
Data Tables & Graphs
Water
Buffered aspirin
Orange juice
Discussion:
When we added acids and bases to water, they changed its pH slowly at first and towards the end of the trial. However, the pH was affected dramatically in between, making the total buffer range encompass over half of the pH scale. In comparison, the buffered aspirin also changed pH more in the middle, but its buffer range was smaller. However buffered aspirin had wildly differing starting pHs, possibly from contamination of the beakers or pH probe from the testing of water. Orange juice followed a completely different pattern than the others, beginning acidic with both the beaker with acid added and the one with the base dropping in pH. The orange juice started out with an even greater difference in pH, and the beaker with base added dropping in pH even more than the acid. This seems to be due to an experimental error and may also be related to contamination of materials. The inconsistencies with the buffered aspirin and the orange juice mean that the results may not be valid estimates of their buffer ranges. More thorough cleaning of material between trials would contribute to making the results more accurate and consistent. The total buffer ranges were generally as expected, with water not resisting change and the other substances more resistant, although the buffered aspirin was predicted to have a smaller buffer range and the orange juice a large one. Most of the other data was not as predicted, with the pattern of the orange juice completely contradicting our expectations.
Conclusion:
In conclusion, all three substances displayed how both biological and non-biological materials are capable of pH resistance even if to only a small degree.
