Turmeric as a Natural Indicator
By: Kaitlyn Soloway, Grant Lynn, Sarah Neal, and Marc Noeh
- The purpose of this project is to make our own natural indicator from turmeric, and be able to make a rough estimate of the pH of various household substances after setting up standards for known pH values ("Red Cabbage Lab").
- Indicators turn different colors in solutions of different pH. All indicators chemically react with hydrogen or hydroxide ions to give a unique color. All indicators have different pH ranges over which it changes shade ("Red Cabbage Lab").
- An acid is an ionic compound that gives off positive hydrogen ions when dissolved in water. A base is an ionic compound that releases a negative hydroxide ion when dissolved in water ("Definitions of Acids and Bases, and the Role of Water")*.
- Household Substances and Predictions
- Evian Bottle Water - slightly basic (8)
- Milk - slightly acidic (6.5)
- Clorox - basic (12)
- Sprite - acidic (3.0)
*see bottom of flyer for citation
Making the Indicator
To turn turmeric into a "liquid" to use as an indicator, we dissolved the turmeric particles in water.
First we transferred these household items from their containers into beakers.
Set Up (Cont.)
Then we added about one inch of each substance into their respective test tubes. Finally we added 20 drops of turmeric into each test tube.
Making the Indicator
Color of Indicator with pH Standards
From right to left:
1 - very light yellow
3 - light yellow
5 - yellow
7 - dark yellow
9 - light orange
11 - burnt orange
13 - red
Initial Color of Indicator
Sprite with Indicator
pH of approximately 3
- We learned from using Turmeric as a natural indicator that it has a transition range somewhere between seven and nine. We know this because when we set up our pH standards, seven was still yellowish, while nine turned orange, meaning somewhere in between must have been the transition range. For acids, the substance became a shade of yellow, while for bases, the substance became a shade of orange or even red.
- Our indicator is better at detecting acids than bases. Since we know our transition range occurs after seven, we know that some bases thus will not be detected. However, since no numbers under seven are in the transition range, all acids will change color.
- One problem encountered with our natural indicator was that there were not many distinct color changes. Since all acids were just different shades of yellow, it was very hard to tell sometimes the difference between colors. Although the shades for the bases were a little more distinct, it still was not easy. Another problem was that we only tested every odd numbered pH. Since our transition range falls somewhere between seven and nine, we could not see the specific range. Further, adding more pH tests would give us more shades of colors to help accurately match substances with the correct pH standards. So if we could make one change, it would be to do many more pH standard tests.
Red Cabbage Lab: We used an in-class lab, titled "Red Cabbage Lab" to help answer questions one and two in the procedure.