• Sara Thompson

The Code of pH Indicators

By Sara Thompson

Special to the Enterprise


pH indicator paper with multiple colors
pH indicator paper with multiple colors; Image credit: Wikimedia Commons user AgrisR

Scientists are often trying to find the pH of the things they are working with. pH indicates how acidic or alkaline a solution is, which can tell us how it will react in experiments. There are many ways to determine pH, with the most precise being measuring the hydrogen ions, but most scientists will use simple indicators that change color depending on if the solution is acidic or alkaline.


One of the easiest and most common ways to test pH is with litmus paper. Litmus paper is made when dyes extracted from lichens are absorbed into filter paper. When litmus paper is dipped in an acidic solution, it turns red, and turns blue if the solution is alkaline. The pH scale goes from 1-14. Solutions that have a pH less than 7 are acidic, with solutions above 7 being alkaline, or basic, and a pH of exactly 7 being a neutral solution.


There are other natural pH indicators as well. The spice turmeric will turn yellow when exposed to acids, and a reddish brown in alkaline. Hydrangeas will have blue blooms if planted in acidic soils and be pink if planted in alkaline soils. A fun way to experiment with indicators at home is to place a red cabbage head in a large bowl and pour boiling water over it. Let the cabbage soak for about a half hour and take the cabbage head out. You can still use the cabbage in cooking or composting as it only interacted with water. What is left in the bowl is the pigment from the cabbage that was extracted into the water. Put some of the cabbage water into some clear glasses, keeping some space at the top. Next, pour a small amount of vinegar into one of the cups, it should turn a pink or red color as you have increased the acidity. In another glass, sprinkle some baking soda into it, it should turn a blue or green color as its alkaline increases. Keep adding more vinegar and baking soda to the solutions to see how the colors change, but be careful, as vinegar and baking soda will react and cause some foam that could spill out and create a mess.


Campers in this week’s Crazy Chemistry camp explored pH with cabbage water. Campers also learned about the different states of matter and did several fun experiments mixing several chemicals that can be found at home. Explorit has extended our After-school camps through May, and plenty of spaces are still available. Camps are Monday-Friday from 3:30-5:30pm for students in grades K-6. Price is $120 Members/$145 Non-Members. Additional information and registration can be found at https://www.explorit.org/camps.


Explorit's coming events:

• Explorit’s Summer Science Camp is back for 2021! Beginning in June and running through to the beginning of August, our camps are filled with fun, hands-on science activities. Summer camp runs from 8:00-11:15am Monday-Friday. Fee for summer camp is $175 for Members/$200 for Non-Members. Available camps are designed for grades K-3, 1-4, and 4-6. Visit https://www.explorit.org/camps for more information and registration.

• Due to COVID-19 restrictions and the health and safety of our staff and visitors, our gallery will remain closed. Staff regularly check messages and email.

• Like many small businesses the closures have had a significant impact on our income and sustainability. Now is a great time to donate and help Explorit continue to educate and inspire the scientists of tomorrow: https://www.explorit.org/donate.

• Continue to support Explorit during this uncertain time by becoming a member. An Exploit Membership not only support us but grants the recipient with free visits to Explorit’s regular public hours, discounts on events, summer and after-school camps, and workshops, and gives you ASTC benefits to visit other museums throughout the world. For more information visit https://www.explorit.org/membership or call Explorit at 530-756-0191.