1. Gas Laws Ideal Gas Laws – Just 2: Boyle’s Law and Charles’ Law
High School Physical Science
Lost Mountain Middle School
Betsy Sanford

2. Characteristics of A Gas
Gases assume the shape and volume of a container
Gases are the most compressible of all states of matter
Gases will mix evenly and completely when confined to the same container
Example: the Earth’s atmosphere (air) is made up of:
78.0% nitrogen
21.0% oxygen
0.93% argon
Trace amounts of neon helium, methane, krypton, hydrogen, xenon, ozone, and water vapor
Gases have lower densities than solids or liquid (less mass per volume)

3. Gas vs. Liquid vs. Solid
Gases have high kinetic energy (move faster) and low attractive force
Liquids have medium kinetic energy (move slow) and medium attractive force
Solids have low kinetic energy (move even slower) and high attractive force

4. Historical Perspective
Gases were the first state of matter studied in great detail
Results of gas experiments are the primary evidence for the theory that all matter is made of atoms
It is the easiest state to understand from a chemistry perspective
Mathematical equations can be generated to explain gas behaviors
Equations work best with “ideal” circumstances (certain ranges of temperature and pressure in the real world)

5. Measurable Properties of Gas
Mass = amount of matter in the gas
Volume = amount of space occupied by the gas
Temperature = the amount of thermal energy (heat) in the gas
Pressure = the amount of force exerted by the gas on another substance

6. Ideal Gases Gas particles move in straight lines, randomly
Average kinetic energy of gas particles depends on temperature (amount of thermal energy)
Gas particles collide and change direction (they may exchange kinetic energy)
Collisions with walls causes pressure
The more collisions the greater the pressure
Gas particles have no volume
There are no attractive or repulsive forces between gas particles
In reality, no gas is “ideal”, but scientists use these principals to create mathematical equations to explain gas behaviors

7. Boyle’s Law Boyle’s Law is all about pressure
When temperature is constant and volume is increased, pressure decreases (an inverse relationship)
When temperature is constant and volume is decreased, pressure increases (an inverse relationship)

8. Charles’ Law Charles’ Law is all about temperature
When pressure is constant and temperature is increased, volume is increased (gases expand when heated)
When pressure is constant and temperature is decreased, volume is decreased (gases contract when cooled)
There is a directly proportional relationship between the temperature of a gas and its volume

9. Importance Human body processes
Scuba diving increases pressure on blood gases; rising too quickly to the surface cause rapid expansion of blood gases; gases bubble out of tissues and cause problems
Vehicle tires
Correct pressure in tires allows durability of tires, tires with too little pressure are less heat resistance, more prone to blow outs, and more likely to get puncture from road debris or potholes

10. Data Set #1 – Graph a GAs Graph the data in the chart.
Which law is demonstrated by this data set?
How do you know?

11. Data Set #2 – Graph a GAs Graph the data in the chart.
Which law is demonstrated by this data set?
How do you know?