What does the term 'reactivity' refer to in chemistry?

• A. The tendency of a substance to undergo a chemical reaction
• B. The color of a substance
• C. The mass of a substance
• D. The smell of a substance

Answer: (A)

Reactivity is about how likely a substance is to participate in a chemical reaction. It describes the tendency to react with other substances, which depends on how easily bonds break and new bonds form, and on factors like electron arrangement, activation energy, temperature, and concentration. The option that states the tendency to undergo a chemical reaction captures this idea best. Color, mass, and smell are observable properties that don’t measure how readily a substance reacts. For example, some metals react vigorously with water, while noble gases show very little reactivity, illustrating how reactivity varies with chemical nature and conditions.