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

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)

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

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)

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

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

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)

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

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

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

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