Question

1. which of the following is a characteristic of all chemical changes? *

a. a different state of matter is produced
b. some mass is converted to energy
c. some form of light is given off
d. a new material is formed

Explanation:

• Option A: A different state of matter can be produced in physical changes (e.g., melting of ice). So, it is not a characteristic of all chemical changes.
• Option B: Mass - energy conversion is significant in nuclear reactions, not in all chemical reactions. Chemical reactions follow the law of conservation of mass (in a closed system, mass is conserved, and the conversion of mass to energy is negligible in chemical reactions compared to nuclear reactions).
• Option C: Some chemical changes do not give off light. For example, the reaction between hydrochloric acid and sodium hydroxide (\(HCl + NaOH=NaCl + H_{2}O\)) is a neutralization reaction and does not give off light.
• Option D: By definition, a chemical change (chemical reaction) results in the formation of a new substance. For example, when hydrogen gas (\(H_{2}\)) reacts with oxygen gas (\(O_{2}\)) to form water (\(H_{2}O\)), a new material is formed.

Answer:

D. a new material is formed