Question

Select the best statement. A. Chemical changes provide the only valid basis for identification of a substance. B. Chemical changes are easily reversed by altering the temperature of the system. C. Chemical changes always produce substances different from the starting materials. D. Chemical changes are associated primarily with extensive properties. E. Chemical changes are accompanied by changes in the total mass of the substances involved.

1) Chemical changes provide the only valid basis for identification of a substance.
2) Chemical changes are easily reversed by altering the temperature of the system.
3) Chemical changes always produce substances different from the starting materials.
4) Chemical changes are associated primarily with extensive properties.
5) Chemical changes are accompanied by changes in the total mass of the substances involved.

Answer 1

The correct statement about chemical changes is that they always produce substances different from the starting materials, involving a transformation at the atomic or molecular level.

Step-by-step explanation:

The best statement regarding chemical changes is C: Chemical changes always produce substances different from the starting materials. Chemical changes involve a transformation where new substances with different properties are formed by breaking and forming bonds between molecules or atoms.

The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction, meaning that chemical changes do not lead to a change in the total mass of the substances involved. Therefore, statements A, B, D, and E are not the best options as they either provide incomplete information or are incorrect.