Week 3 Lecture 1
Solutions at the bottom.

1)  In-video quiz at timepoint 01:58.

 "The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons."

- Wikipedia, atom, http://en.wikipedia.org/wiki/Atom

"A molecule /ˈmɒlɪkjuːl/ is an electrically neutral group of two or more atoms held together by chemical bonds."

- Wikipedia, molecule, http://en.wikipedia.org/wiki/Molecule

2)  In-video quiz at timepoint 10:36.

"In physics, a wave is a disturbance or oscillation that travels through space and matter, accompanied by a transfer of energy. Wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass transport."

- Wikipedia, wave, http://en.wikipedia.org/wiki/Wave