Review the use of units to describe amounts of large items. Discuss the need for a unit to describe and count small objects, like atoms and molecules. Introduce the concept of the mole. Define how it is based on carbon 12. List the mole as 6.02 x 10e23 particles. View a video on the determination of a mole and how large the number actually is. Run problems which solve for the number of particles, atoms, and/or molecules of specific chemicals. Show how to best set up a ratio which can be used to calculate the number of particles.