Turmeric is a natural indicator. On adding its paste to acid and base separately, which color is observed?

A. yellow in both acid and base

B. yellow in acid and red in the base

C. Pink in acid and yellow in the base

D. Red in acid and blue in the base.

Turmeric is indeed a fascinating natural indicator, and it reacts differently when mixed with acids and bases. When you add turmeric paste to an acid, such as lemon juice or vinegar, it retains its yellow color. However, when you introduce it to a basic solution, like baking soda or soap, it changes to a reddish-brown hue. Therefore, the correct answer to your question is B: yellow in acid and red in the base.

Understanding Turmeric as a Natural Indicator

Turmeric contains a compound called curcumin, which is responsible for its vibrant yellow color. This compound is sensitive to pH changes, which is why turmeric can be used as a natural pH indicator. Let's break down how it works in different environments:

Reaction with Acids

When turmeric is mixed with an acidic solution, the pH level is low (below 7). In this environment, the curcumin remains stable and retains its characteristic yellow color. This is why you observe:

• Color in Acid: Yellow

Reaction with Bases

In contrast, when turmeric is added to a basic solution, the pH level rises (above 7). The alkaline environment causes a structural change in the curcumin molecule, resulting in a color shift. This is where you see:

• Color in Base: Red

Practical Applications and Examples

This property of turmeric can be demonstrated easily at home or in a classroom setting. For instance, if you mix turmeric powder with water and then add a few drops of vinegar, you will see that the mixture remains yellow. On the other hand, if you add a small amount of baking soda to another turmeric solution, it will turn reddish-brown. This simple experiment not only illustrates the concept of pH indicators but also highlights the versatility of natural substances in chemistry.

Why Use Natural Indicators?

Natural indicators like turmeric are beneficial for several reasons:

• They are non-toxic and safe to use.
• They are easily accessible and inexpensive.
• They provide a visual representation of pH changes, making learning interactive and engaging.

In summary, turmeric serves as an excellent natural indicator, showcasing a vibrant yellow color in acidic conditions and transitioning to red in basic environments. This property not only enhances our understanding of pH levels but also encourages the use of natural materials in scientific exploration.