Cherries as a Natural Indicator
Kyle Clough, Justin Gorden, Missy Iio, Sarah Liang, Harry Wise
The purpose of this lab is to find a natural substance that acts as an acid/base indicator using sprite, water, vinegar, and bleach. An acid is a substance which dissociates into H+ ions among other ions. A base dissociates into OH- ions among other ions. An indicator reacts with these H+ or OH- ions and changes color because either the acid or base form of the indicator becomes dominant. The acid form becomes dominant when there is a high H+ concentration and the base form becomes dominant when there is a high OH- concentration.
Before
We began with raw cherries.
After
We pulverized the cherries, then forced them through a coffee filter to extract the juices. This juice was our finished indicator.
Experimental Setup
In order from left to right the substances are sprite, bleach, vinegar, and water. These are the substances for which we experimentally determined the pH.
Experimental Setup
In order to determine the pH of the four aforementioned substances, we prepared a set of pH standards. We added our natural indicator to seven substances to identify the color which the indicator turned at varying known pH levels. With this known, we could then determine the pH of the experimental substances based on the color which the indicator turned.
Indicator
The initial color of the indicator was dark red.
Standards
The pH of the standards are from left to right as follows: 1, 3, 5, 7, 9, 11, 13.
Initial Household Substances
The household substances were initially clear and colorless. From left to right they were sprite, bleach, vinegar, and water.
Household Substances After Testing
Below from left to right:
The sprite had a pH of approximately 3.
The bleach had a pH of approximately 12.
The vinegar had a pH of approximately 2.
The water had a pH of approximately 7.5.
Conclusions
Acids resulted in red and variants of red in the indicator. Bases resulted in a range of green, brown, yellow-brown, and red-brown. Cherries are better at indicating bases, as the variation of color between pH levels is more pronounced. When in the presence of an acid, the indicator only changed color within the range of pink to red. Whereas when in the presence of a base, the indicator ranged from red to brown to green. The issue with judging the pH came when trying to discern the pH level of the acidic substances we used. It was difficult to assign them a definite pH level as the colors in the acidic range do not vary much. If we were to do this experiment again, we would choose more alkaline substances than acidic substances because it is easier to determine the pH of a base with cherries as a natural indicator.