Lessons 15 and 16

Lesson 15
In this lesson we learned about number density and air pressure. Air pressure can be determined by measuring the difference in height of a liquid. We also learned the formula for number density, which is pictured below.

Practice Problems
1. Air is less dense as altitude increases. Both the pressure and temperature is less as atltitude increases.


Lesson 16
In this lesson we learned about moles. A mole is a unit used to keep track of very large numbers.
1 mole= 602,200,000,000,000,000,000,000 We also learned about standard temperature and pressure (STP). 1 atm = 273 K and 1 mole = 22.4 L at atm. Equal volumes of gases have equal numbers of gas particles if temperature and pressure are the same.

Practice Problems
1. Chemists invented the mole in order to keep track of the insanely large number of particles in substances