# Lesson 2 The Kinetic Molecular Theory & Pressure

```12/16/2015
The Kinetic Molecular Theory &amp;
Pressure
Learning Goals:
I will be able to explain the states of matter using the KMT.
I will be able to explain pressure and atmospheric pressure.
The Gas State
Takes the shape and volume of the container
Highly compressible
Flows easily
Random movement (called Brownian Motion after
Brown’s work from early 1800s)
1
12/16/2015
The Kinetic Molecular Theory (KMT)
All substances are composed of particles that are in
constant, random motion.
It is because of this motion that the scent of baking
Temperature
Temperature is a measure of the average kinetic energy
of the entities of a substance.
So…as the particles move faster, the temperature
increases.
2
12/16/2015
Pressure
Is the force per unit area
The SI unit is the Pascal (Pa)
Atmospheric Pressure
Is the pressure exerted by air on ALL objects.
We use kilopascals (kPa)
3
12/16/2015
Some Standards…
Standard Temperature &amp; Pressure (STP)
• 0&deg;C
• 101.325 kPa
• Standard Ambient Temperature &amp; Pressure (SATP)
• 25&deg;C
• 101 kPa
Atmospheric Pressure &amp; Altitude
The density of gases decreases as altitude increases, so
atmospheric pressure decreases as altitude increases.
4
12/16/2015