Can a chemical reaction take place without reacting its activation energy point? why or why not?

Describe the difference between a. a hypothesis and a theory and b. an observation and an experiment.

This image is an example of a(n) a) atom. b) compound. c) mixture. d) molecule.

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.