Which of the following is a common reason for a color change during a chemical reaction?

• A. Increase in temperature without any chemical change
• B. Formation of a new substance with different electronic structure
• C. Evaporation of the solvent
• D. Physical mixing of two colorless substances

Answer: (B)

Verified step by step guidance

1. Understand that a color change during a chemical reaction typically indicates a change in the electronic structure of the substances involved, which affects how they absorb and emit light.
2. Recognize that an increase in temperature alone, without any chemical change, usually does not cause a permanent color change because it does not alter the molecular structure.
3. Note that evaporation of the solvent is a physical change and generally does not produce a new color unless the solute itself changes chemically.
4. Consider that physical mixing of two colorless substances is a physical process and does not create new substances with different electronic structures, so no color change is expected.
5. Conclude that the formation of a new substance with a different electronic structure is the common reason for a color change during a chemical reaction, as new compounds absorb and reflect light differently.