Chapter 13 States of Matter Notes #7B

Gases Gases often act similar to each other at room temperature, regardless of their different compositions. The Kinetic-Molecular Theory is used to describe the behavior of gases and particle motion.

Kinetic Molecular Theory 1. Gas particles do not attract or repel each other

Kinetic Molecular Theory 2. Gases are made of extremely small particles that are separated by large amounts of space.

Kinetic Molecular Theory 3. Gas particles are in Constant random motion.

Kinetic Molecular Theory 4. Gas particles are constantly moving in a straight line, until another particle hits them and changes their direction with elastic collisions Elastic Collision (no energy is lost)

Kinetic Energy 5. All gases have the same average kinetic energy at a given temperature KE = ½ mv2 KE = kinetic energy m = mass v = velocity

Behavior of Gases Low density ( D=m/v ) gases have much less mass contained in the same amount of space as a liquid or a solid.

Behavior of Gases Compression and Expansion: gases are compressible because of the large amount of space between the particles. Gasses expand because of the random motion of particles.

Diffusion and Effusion Behavior of Gases Diffusion and Effusion Diffusion: Gas particles moving and mixing randomly until they are evenly distributed. Effusion: (related to diffusion) When gas particles escape through a tiny opening and the time it takes (rate) for the gas to escape can be measured.

Thomas Graham Thomas Graham: Born in Scotland in 1805. Studied effusion using a glass tube filled with water and different gases.

Graham’s Law of Effusion Basically… heavier molecules are going to move (effuse/diffuse) slower than lighter particles at the same temperature.

Gas Pressure Force per unit area As gas particles collide (hit) the walls of their container, they create a pressure. Remember: a single gas molecule does not create very much pressure by itself, but how many particles are there in one mole of any gas at STP?

Gas Pressure The air we breathe is a gas, so it also creates a pressure on its surroundings (atmospheric pressure).

Barometer vs. Manometer Barometer: Instrument used to measure atmospheric pressure. Manometer: Instrument used to measure pressure in a closed container.

Gas Pressure Units Standard Temperature and Pressure (STP) Standard Temp = 0oC and 273 K Standard Pressure = 101.3 kPa, 1 atm, 14.7 PSI, 760 mm Hg, 760 Torr, 101,300 Pa Note: the pascal(Pa) is the SI Unit for Pressure. 1Pa = 1N/m2

Standard atmospheric pressure Conversions Gas Pressure Units Standard atmospheric pressure Conversions 101.3 kPa 760 mmHg 760 torr 1 atm 14.7 psi = = = = = Table 13-1

Dalton’s Law of Partial Pressure The total pressure of a mixture of gases is equal to the sum of the partial pressures of all the gases in a mixture PTotal = P1 + P2 + P3 + …

Dalton’s Law of Partial Pressure Practice Problems – page 392

13.2 Forces of Attraction INTRAmolecular Forces – this is the attractions within a particle: - ionic bonds - covalent bonds - metallic bonds

Forces of Attraction INTERmolecular Forces – this is the attractions between particles: - dispersion forces - dipole-dipole forces - hydrogen bonds *Intramolecular forces are stronger than intermolecular forces Weakest To Strongest

13.3 Liquids & Solids Liquids – more dense than gases. Can be compressed, however the change in volume is less than that of gases. Fluidity – ability to flow Viscosity – measure of the resistance to flow. Viscosity varies with temperature.

13.3 Liquids & Solids Surface Tension – measure of inward pull by interior particles

13.3 Liquids & Solids Capillary action – Spontaneous rising of a liquid in a narrow tube. Cohesion – force between particles Adhesion – force between particles and container

13.3 Liquids & Solids Solids – more closely packed than liquids – not necessarily more dense Crystalline solid – a solid whose atoms, ions, molecules are arranged in an orderly geometric shape. There are 5 types of crystalline solids.

13.3 Liquids & Solids Table 13-4 page 402. 1. Atomic 2. Molecular 3. Covalent Network 4. Ionic 5. Metallic Amorphous Solid – non crystalline solids

13.3 Liquids & Solids Amorphous solid – a solid whose particles are not arranged in a regular repeating pattern. Example: glass, rubber, plastics