# PACS 2008 Unit: Gases Mr. Nylen Pulaski Academy High School 2008.

## Presentation on theme: "PACS 2008 Unit: Gases Mr. Nylen Pulaski Academy High School 2008."— Presentation transcript:

Common Properties of Gases Have mass and occupy space (volume) Easily compressed Exert pressure Diffuse through each other readily Fill their containers completely Have no definite shape and volume Gas pressure is temperature dependent

Prove the following in small groups… Gases have mass Gases have mass Gases occupy space Gases occupy space Gases exert pressure Gases exert pressure Gases have no definite shape or volume Gases have no definite shape or volume Gas pressure is temperature dependent Gas pressure is temperature dependent PACS 2008

Gas Pressure Pressure is equal to Force per Unit of Area P=Force/Area psi? Units: Pascals Psi Torrs Atmospheres Bars mmHg Inches Hg

Atmospheric Pressure Weight of air pushing down on you Barometers: Measure air pressure As air pressure increases, column of Hg rises Standard Pressure Average air pressure at sea level – normal air pressure 760 mmHg, 760 torr, 1 atm, 101.3 kPa, 14.7 psi

Kinetic Molecular Theory All gases are made up of particles that have mass All gases are made up of particles that have mass Constant, rapid, random, straight-line motion Constant, rapid, random, straight-line motion Separated by large distances Separated by large distances Frequent, elastic collisions with walls of container Frequent, elastic collisions with walls of container Exert no force of attraction for each other Exert no force of attraction for each other PACS 2008

Activity Page 3

Converting pressures Uh Oh, Factor Label Method AGAIN! Uh Oh, Factor Label Method AGAIN! Use these steps: Use these steps: Write the current unit and what you want to convert into (760 mmHg to psi) Write the current unit and what you want to convert into (760 mmHg to psi) Write the conversion factor to go between the two units (14.7 psi is 760 mmHg) Write the conversion factor to go between the two units (14.7 psi is 760 mmHg) Use factor label method to cancel units Use factor label method to cancel units PACS 2008

Activity Page 4 PACS 2008

Lab – Exploring Gas Laws

Gas Laws Boyle’s Law Relates P and V As pressure increases, volume decreases Charles’ Law Relates T and V As temperature increases, volume increases Guy-Lussac’s Law Relates T and P As temperature increases, pressure increases

Practice What are 2 ways you can increase pressure of a gas? What are 2 ways you can increase pressure of a gas? If temperature is held constant, and pressure increases, what must be happening to volume? If temperature is held constant, and pressure increases, what must be happening to volume? If volume is held constant, how can I change temperature? If volume is held constant, how can I change temperature? If volume is held constant, how can I change pressure of a gas? If volume is held constant, how can I change pressure of a gas? PACS 2008

Charles Law Demo PACS 2008

Lab Design a poster illustrating one of the following Design a poster illustrating one of the following Boyle’s Law Boyle’s Law Charles law Charles law Guy-Lussac’s Law Guy-Lussac’s Law Kinetic Molecular Theory Kinetic Molecular Theory PACS 2008

Combined Gas Law PACS 2008

Ideal Gas Theoretical model used to explain REAL gas behavior Theoretical model used to explain REAL gas behavior Perfect gas – behaves according to the gas laws perfectly, without exception Perfect gas – behaves according to the gas laws perfectly, without exception PACS 2008

Real Gas Behave like ideal gases MOST of the time Behave like ideal gases MOST of the time Gas molecules appear to have no volume and no attraction forces Gas molecules appear to have no volume and no attraction forces In reality, all particles are somewhat attracted to each other In reality, all particles are somewhat attracted to each other PACS 2008

Deviations from Ideal Gas When particles become closer together When particles become closer together Low temperature Low temperature High pressure High pressure Gas laws can’t predict behavior accurately at extremely low temps and extremely high pressures Gas laws can’t predict behavior accurately at extremely low temps and extremely high pressures PACS 2008

Practice Which gas is most like an ideal gas (think size of molecule, how fast it can move, etc). Which gas is most like an ideal gas (think size of molecule, how fast it can move, etc). A. NH 3 A. NH 3 B. H 2 B. H 2 C. CO 2 C. CO 2 D. N 2 D. N 2 PACS 2008

Homework Take out page 28 Take out page 28 We’ll be going over it We’ll be going over it Go over page 24 Go over page 24 PACS 2008

Review Work through Page 25-27 in notes Work through Page 25-27 in notes PACS 2008

Review game PACS 2008