Which of the following describes the mixture of materials that exhibits a range of colours in acidic, basic, and neutral solutions?

Indicators

The correct answer is 2. Indicators.

Indicators are substances or mixtures of materials that undergo a visible change in color in response to changes in the acidity or basicity (pH) of a solution. These changes in color are particularly noticeable in acidic, basic, and neutral solutions. Indicators are commonly used in chemistry and biology to determine the pH of a solution qualitatively.

Here is how indicators work and exhibit a range of colors in different pH conditions:

1. Acidic Solutions:  In acidic solutions, indicators often take on one color. Commonly, this color is a shade of red. The specific color can vary depending on the indicator used.

2. Neutral Solutions:  In neutral solutions, indicators may exhibit a different color, often different from the color observed in acidic conditions. The color in neutral solutions can be a transition between the acidic and basic colors.

3. Basic Solutions: In basic (alkaline) solutions, indicators may display another distinct color, commonly a shade of blue or green.

One well-known example of an indicator is litmus paper. Litmus paper turns red in acidic solutions, and blue in basic solutions, and may have a transition color in neutral solutions.

Other indicators include phenolphthalein, bromothymol blue, and methyl orange, each with its own set of color changes at different pH levels. Indicators play a crucial role in determining the acidity or basicity of a solution, especially when precise pH measurement is not required.