UNDERSTANDING KMT USING GAS PROPERTIES AND STATES OF MATTER Learning Goals: Students will be able to describe matter in terms of particle motion. The description should include Diagrams to support the description. How the particle mass and temperature affect a gas How the size and speed of gas particles relate to everyday objects What are the differences and similarities between solid, liquid and gas particle motion

If you have a bottle with Helium & Nitrogen at room temperature, how do the speed of the particles compare? A. All have same speed B. The average speeds are the same C. Helium particles have greater average speed D. Nitrogen particles have greater average speed

Light and heavy gas at same temperature 300K Speed of each particle varies!!

What happens if you add energy using the heater? A. All atoms speed up B. All atoms speed up about the same C. The lighter ones speed up more D. The heavier ones speed up more

answer Heavy  Light 

Which is most likely oxygen gas? ABCABC

Which is most likely liquid water? ABCABC

How many water molecules are in a raindrop(.5 cm diameter). The molecules are about.1nm If we just look at how many are across.005m/.1E-9m = 5E7 or 50 million.

To show vibration mistry/Spectroscopy/Vibrational_Spectroscopy/ Vibrational_Modes mistry/Spectroscopy/Vibrational_Spectroscopy/ Vibrational_Modes

KINETIC MOLECULAR THEORY: WHY GASES BEHAVE THE WAY THEY DO Unit 7

Kinetic Energy Kinetic energy: the energy an object possesses due to its motion.

5 assumptions of KMT 1. Gases consist of large number of particles that are in CONTINOUS, RANDOM motion. 2. Gas molecules take up ZERO space (have no volume).

5 assumptions of KMT 3. Gas molecules do not attract or repel one another.

5 assumptions of KMT 4. When molecules collide, energy is conserved and they are perfectly elastic (no energy is lost). Elastic collision vs inelastic collision

5 assumptions of KMT 5. The average kinetic energy of the molecules is proportional to the temperature. The higher the temp., the more the kinetic energy.

Average Molecular Speed vs Temp.

Pressure Force: mass of an object times its acceleration F = mass*acceleration Pressure: Force per unit area P = Force/Area With gases, pressure is created by the moving molecules (force) hitting the walls (area) of the container.

Pressure Force: mass of an object times its acceleration F = mass*acceleration Pressure: Force per unit area P = Force/Area With gases, pressure is created by the moving molecules (force) hitting the walls (area) of the container.

Atmospheric Pressure

Units of pressure 1 Atm = 760 torr = 760 mmHg = kPa = 14.7 lb/in 2 These are equivalent measurements, which means we can convert!

Units of pressure 1 Atm = 760 torr = 760 mmHg = kPa = 14.7 lb/in 2 These are equivalent measurements, which means we can convert!

Units of pressure 1 Atm = 760 torr = 760 mmHg = kPa = 14.7 lb/in 2 These are equivalent measurements, which means we can convert!

Pressure conversion practice

Oh yeah, temperature conversions too… Kelvin = °C Kelvin does not have a degree sign

Oh yeah, temperature too… Kelvin = °C Kelvin does not have a degree sign

Oh yeah, temperature too… Kelvin = °C Kelvin does not have a degree sign

HEATING CURVES AND PHASE DIAGRAMS Unit 7

Heating/Cooling Curves A  B All solid, temperature is rising toward the melting point

Heating/Cooling Curves B  C Solid and liquid present. Temperature is constant until ALL solid is melted then…

Heating/Cooling Curves C  D Only liquid present. Temperature is rising towards boiling point.

Heating/Cooling Curves D  E Liquid and gas present. Temp. is constant until ALL has been converted to gas then…

Heating/Cooling Curves E  F Only gas present. Temp. will continually rise

Heating/ Cooling Curves Definitions: Heat of Fusion: energy needed to change between a solid to liquid or vice versa (B  C) Heat of Vaporization: energy needed to change between a liquid to gas or vice versa (D  E)

Mr. Sacre this is black magic… Why does temperature stay constant even though we are still heating? Remember, solid and liquids molecules have attractive forces between their particles. These are called intermolecular forces.

Intermolecular forces examples

Mr. Sacre this is black magic… We must break these intermolecular forces. Breaking bonds requires energy. Thus the heat being added breaks these bonds instead of raising temperature

Not black magic…its science! Heat goes into phase change Heat goes into temperature change

How would a cooling curve look?

Phase Diagrams

Phase Diagram: summarizes the effect temperature and pressure of a substance in a closed container. Triple Point: specific temperature and pressure at which all 3 states of matter are present.

Phase Diagrams To remember which areas are for what state: Think of the conditions that will most likely result in that state being present. i.e. lots of pressure will shove particles close together, at low temp. particles are barely moving, that sounds like a solid.

This might be my favorite thing ever…

THE GAS LAWS

Boyle’s Law

How does the KMT explain this? Constant temp. mean particles aren’t moving any faster. Smaller volume means more collisions with the walls of the container, hence the greater pressure.

Applications of Boyle’s Law Breathing Syringes Cartesian Diver

Charles’ Law

How does the KMT explain this? Pressure is constant, so number of collisions with the walls are the same. Higher temp. makes the particles move faster, so the number of collisions SHOULD increase. To keep this from happening the volume needs to increase to compensate.

Applications of Charles‘ Law Hot vs Cold Balloon (Deflated Footballs?)

Combined Gas Law

THE IDEAL GAS LAW

Why Ideal? Hopefully you can see that MANY things effect gases. This makes it very difficult to study the behavior of gases. The Ideal gas law is ONLY A MODEL used by chemists to better understand gases under much simpler conditions, outside the realm of the REAL world. Ideal means we must follow all assumptions made by the KMT.

PV = nRT

Other Variations: Deriving Molar Mass

Other Variations: Deriving Density

Limitations to the Ideal Gas Law Works great for low pressures and high temperatures Most gases do not behave ideally above 1 atm -KMT assumes gases have no volume