Which of the following best describes whether a chemical change can be undone?

• A. Most chemical changes cannot be easily reversed because new substances are formed.
• B. All chemical changes can be undone by simply cooling the substance.
• C. Chemical changes are always reversible by physical means.
• D. Chemical changes can be undone by dissolving the products in water.

Answer: (A)

Verified step by step guidance

1. Understand the definition of a chemical change: it involves the formation of new substances with different properties from the original substances.
2. Recognize that because new substances are formed, reversing a chemical change typically requires another chemical reaction, not just physical processes.
3. Evaluate the options: cooling a substance is a physical change and does not reverse chemical changes; dissolving products in water is a physical process and does not reverse the chemical transformation.
4. Conclude that most chemical changes cannot be easily reversed because the original substances no longer exist in their initial form.
5. Therefore, the best description is that most chemical changes cannot be easily reversed because new substances are formed.