What is the significance of temperature change in chemical reactions?

• A. It is evidence used to infer energy transfer during a reaction.
• B. It is the only factor determining reaction rate.
• C. It has no relation to energy.
• D. It always increases during a reaction.

Answer: (A)

Temperature change is a direct sign that energy is moving between a reaction and its surroundings. When bonds break and new bonds form, energy is either released (exothermic) or absorbed (endothermic). That transfer of energy shows up as a rise or fall in temperature of the reacting system or the solution. Because of this, measuring how much the temperature changes lets you infer how much energy has been transferred, and you can even estimate the amount of heat using Q = m c ΔT (mass, specific heat, and the temperature change). The idea is not that temperature alone controls how fast a reaction goes—that depends on factors like concentration, surface area, and catalysts—but that the temperature change tells you about the energy exchanged during the reaction. And temperature doesn’t always rise: an endothermic process can cool the surroundings, while an exothermic process can raise them.