All matter that we encounter in everyday life exists in at least one of three physical forms.

Embryos of different species look very similar, which shows that the organisms share a ancestor.

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.

When balancing a chemical equation: