colorless vinegar added to purple cabbage juice turns pink What is the reason behind and why is it considered a chemical change?
Red cabbage juice contains a chemical (a flavin) called anthrocyanin. It turns a different color in acid and basic solutions. The chemical change is the switch from the acid to the base form.
The reason for colorless vinegar turning pink when added to purple cabbage juice is due to a chemical change called an acid-base reaction. Purple cabbage contains a pigment called anthocyanin, which is responsible for its purple color. Anthocyanins have different colors based on the pH of the solution they are in.
When colorless vinegar (which is an acid called acetic acid) is added to purple cabbage juice (which is slightly basic), it reacts with the anthocyanins in the cabbage juice. This reaction causes a change in the pH, resulting in a color change from purple to pink.
This is considered a chemical change because the reaction alters the chemical composition of the substances involved. The interaction between the acid and the base causes the molecules to rearrange and form new substances. In this case, the reaction between acetic acid and the anthocyanins leads to a new color being produced, indicating a chemical change has occurred.
The reason behind colorless vinegar turning purple cabbage juice pink has to do with the presence of a compound called anthocyanin in purple cabbage. Anthocyanin is a pigment that gives the cabbage its characteristic purple color. When the cabbage juice is at its natural pH, the anthocyanin molecules are in a form known as flavylium cation, which appears purple.
However, when vinegar, which is an acid, is added to the cabbage juice, it lowers the pH of the solution. The acid from the vinegar reacts with the flavylium cation, causing it to lose a hydrogen ion (H+). This results in a shift in the molecular structure and the formation of a new compound called the quinoid base. The quinoid base appears pink in color instead of purple.
This phenomenon is considered a chemical change because the reaction between the acid in vinegar and the flavylium cation in cabbage juice leads to the formation of a completely new compound with different properties, including a change in color. Chemical changes involve the breaking and forming of chemical bonds, resulting in the creation of new substances. In this case, the color change indicates a change in the composition of the solution, making it a chemical change rather than a physical change.