Tutor profile: Dan S.

What causes a chemical reaction?

A chemical reaction occurs when one atom gives part of itself to another atom. Atoms are made of protons (positive parts), electrons (negative parts), and neutrons (neutral parts), and their parts are not always in balance. Like us, they seek to balance themselves by giving parts of themselves away to another atom that may need some extra electrons, for example. This happens with such speed and force that a great deal of energy is released, resulting in a chemical reaction.

Are all animals related? How did they evolve?

Yes, all animals are related! Every extant organism evolved in some way from an "LCU" (last common ancestors) that most scientists believe was a single cell. All living things have DNA- the information-packed molecule that tells your cells what to do- and we can study how this DNA "mutated" (or changed over time) to understand who an organism evolved from, and when.

When is the right time to use a comma?

Any time there is a pause, a new thought, or your listing something. That's it!