Why does red cabbage juice change color when it comes into contact with different substances?

  Students in Teacher Harvey’s M3 Science class explored the properties of red cabbage juice as a natural pH indicator. They learned that the pigment anthocyanin in red cabbage juice is sensitive to hydrogen ion concentration, causing the indicator to change color at different pH levels. Students tested a variety of everyday materials, including lemon juice, vinegar, Sprite, hydrochloric acid, instant coffee, antacid tablets, alkaline water, washing powder, soap, and baking soda, and observed the different color changes produced by each sample. They learned that substances producing a reddish color indicate acidic conditions, while those changing to green or blue indicate basic/alkaline conditions. Through this hands-on investigation, students connected visible color changes with pH and the properties of acids and bases.