GASES

Aim 1: To review properties of the states of matter and to assign them levels of entropy.

Entropy Entropy = disorder, randomness Nature loves to increase entropy! … increases when… - temperature increases -something dissolves (becomes aqueous) - highest in gases

States of Matter--Solids Particle arrangement: Close, ordered, vibrate in place Intermolecular forces of attraction: strong, high forces are hard to separate Shape: definite Volume: definite Entropy: low

Liquids Particle arrangement: less ordered, flow around each other Intermolecualar forces of attraction: medium Shape: takes the shape of the container Volume: definite Entropy: medium, can be increased by dissolving matter into the liquid

Gases Particle arrangement: Far apart, random movement Intermolecular forces of attraction: low, molecules are not close together to feel an attraction Shape: takes the shape of the container Volume: Uniformly fills the container, COMPRESSIBLE** Entropy: high

More on Solids—Two Categories Amorphous solids are “solids without form” AKA Glass

Crystalline solids have the crystal lattice structure and are considered “true” solids

More on Liquids– Two Properties Volatile Liquids are those that easily evaporate and therefore have weak intermolecular forces

Liquids Viscous liquids: liquids that resist motion whenever they move past each other– Think molasses Stronger attractive forces= higher viscosity Increasing temperature causes molecules to move faster so they have less resistance!

STP Standard Temperature and Pressure TABLE A 273K =_________DC 1 atm and 101.3kPa

Aim 2: To predict the behavior of gases according to their properties.

Gases Gases can be elements, compounds, or mixtures All gases behave in similar ways. Not all gases are colorless.

Gases Gases collide into the walls of the container which exerts pressure. Gases have low density and mass.

Volume The volume of a gas is equal to its container. Usually measured in L or mL  

Temperature KELVIN ONLY!!!!!! K=C+273 this is on table T Standard temperature=273K

78DC= _____________K 900 K=________________DC Which is colder, 65 DC or 354 K?

Pressure Gas particles exert pressure by colliding into the walls of the container. More collisions=higher pressure Standard pressure= 1atm=101.3kPa

Aim 3: To predict the behavior of gases using different gas laws.

Boyle’s Law P1V1=P2V2 ONLY compares P and V Amount of gas and T remain constant States: volume and pressure are inversely related.

Boyle As P___________ V_____________ and as P____________ V _____________

What happens to the volume that the gas occupies when the piston is pushed down?   What happens to the volume that the gas occupies when the piston is raised?

When volume is increased, particles will have decreased collisions with the container walls, and therefore pressure will decrease. When volume is decreased, particles will have increased collisions with the container walls, and therefore pressure will increase.

Animation 1. A sample of gas has a volume of 34.2 L when its pressure is 1.49 atm. What volume will the gas occupy at 2.7 atm if temperature remains constant?

2. If 50. 0L of hydrogen gas is exerting a pressure of 105 2. If 50.0L of hydrogen gas is exerting a pressure of 105.8 kPa has its volume expanded to 75.0 mL, what would the new pressure of the hydrogen gas be?

Charles’ Law (V1 = V2) T1 T2 Compares V and T Amount of gas and Pressure remain unchanged States: volume and temperature of a gas are directly related.

As T __________V __________  

If temperature is increased, particles will move more rapidly If temperature is increased, particles will move more rapidly. Volume will increase so the number of collisions with the container wall will increase

Charles’ Animation

Practice 1. A sample of gas occupies 500. mL at 313K and 1atm. What volume will this gas occupy at STP? 2. Calculate the final volume when a 150.0 mL sample of neon gas at 288K is cooled to standard temperature and pressure is constant.

Guy-Lussac’s (P1 = P2) T1­ T2 Compares P and T Amount of gas and Volume remain constant States: the pressure of a fixed mass of gas varies directly with Kelvin temperature As T__________P___________

If temperature is increased, particles will move more rapidly If temperature is increased, particles will move more rapidly. This leads to increased number of collisions with the container which means the pressure increases.

Practice 1. A gas exerts 200.0kPa at 323K. At what temperature will the pressure be 126.5 kPa? 2. If neon gas exerts a pressure of 1.25 atm at 301 Kwhat would the temperature be if the pressure is changed to 725 mmHg?

P T V