Which statement describes one of the main differences between a physical and a chemical change?

• A. A chemical change results in the formation of new substances, while a physical change does not.
• B. Both physical and chemical changes always produce energy in the form of heat.
• C. A chemical change can be easily reversed, but a physical change cannot.
• D. A physical change always involves a change in chemical composition.

Answer: (A)

Verified step by step guidance

1. Understand the definitions of physical and chemical changes: A physical change affects the form or appearance of a substance but does not change its chemical identity, while a chemical change results in the formation of one or more new substances with different chemical properties.
2. Identify key characteristics of physical changes: These include changes in state (such as melting or boiling), shape, or size, without altering the substance's chemical composition.
3. Identify key characteristics of chemical changes: These involve breaking and forming chemical bonds, resulting in new substances with different chemical formulas and properties.
4. Evaluate the given statements by comparing them to these definitions: For example, check if the statement about energy production applies to both changes or if reversibility is a distinguishing factor.
5. Conclude that the main difference is that chemical changes produce new substances, whereas physical changes do not, making the statement 'A chemical change results in the formation of new substances, while a physical change does not' the correct description.