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Understand the Kinetic-Molecular Theory through activities and models. Learn about gas behavior, pressure, temperature, and diffusion. Explore concepts like diffusion, effusion, gases in motion, and ideal gas model.
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Chapter 10 • The Kinetic-Molecular Theory is based on the idea that particles of matter are always in motion. • The constant motion of particles mean they have kinetic energy. • Their kinetic energy can be used to explain the different states of matter, (solid, liquid, and gas) and their properties.
ENGAGE - Syringe Activity 1. Pull the plunger of a syringe out as far as it will go without coming out. 2. Put your finger on the end of the syringe (where a needle would go) 3. Push the plunger down. 4. What happens? Draw a picture if needed. 5. Explain why this happens. Use a picture to help explain if needed.
Lemon Initial Model - If I cut open a lemon, draw a model to show what happens that allows you to smell the lemon across the room.
The Kinetic Theory of Gases The Ideal Gas Model explains how ideal gases behave. SIZE: - tiny particles (so small, considered to have no size relative to each other) • far away from each other • no attraction or repulsion
MOTION: • Particles are in constant, rapid, and random motion. • When they collide no energy is lost (elastic collisions) • When they collide with the walls of a container, they cause pressure.
ENERGY: - Kinetic Energy of gases is determined by: KE = 1/2 mv2 M= mass v= velocity - Temperature is a measure of the average kinetic energy of the gas particles.
Pressure: Measured using: Barometer
Units of Pressure(you will need to be able to convert between these units!) - All of these values are equal to each other
Units of Pressure(you will need to be able to convert between these units!) Example 1: convert 540.0 mmHg to pa
Units of Pressure(you will need to be able to convert between these units!) Example 1: convert 540.0 mmHg to pa 540.0 mmHg x 101,325 pa = 760 mmHg 71994.0 71990 pa
Example 2: convert 50.0 psi to atm Example 3: If a balloon has a pressure of 1,205 torr, how many Kilopascals does this equal?
Example 2: convert 50.0 psi to atm 50.0 psi x 1.0 atm 14.7 psi = 3.40 atm Example 3: If a balloon has a pressure of 1,205 torr, how many Kilopascals does this equal? 1,205 torr x 101.325 Kpa 760 torr = 160.7 Kpa
Absolute zero= lowest possible temperature at which molecules stop moving. = 0K or -273C STP (Standard Temperature and Pressure): STP is the "standard" conditions often used for measuring gas density and volume. At STP, 1 mole of any gas occupies 22.4 T = 00C or 273K P= 1 atm Temperature Review:
Temperature conversions: K = C + 273 C = K - 273 Ex. 1: Convert 400.0 K to Celsius Ex. 2: Convert 60.0 0C to Kelvin
Temperature conversions: K = C + 273 C = K - 273 Ex. 1: Convert 400.0 K to Celsius C = 400 – 273 = 127.0 0C Ex. 2: Convert 60.0 0C to Kelvin K = 60 + 273 = 333 K
Demonstration: diffusion and KMT • What do you predict what will happen to a drop of food colouring that is added to each graduated cylinder- one HOT one COLD? • 2. What is happening in each graduated cylinder at the macroscopic (visual) level? • 3. What is happening in each graduated cylinder at the particle level? MODEL THIS! • 4. What do you think the graduated cylinders will look like by the end of class? Explain why this happens.
Molecular Effusion and Diffusion • Gas particles are always moving • Their speed depends on the mass of particles • On average lighter gases move FASTER than heavier gases(have same average kinetic energy so they need higher velocity to make up for less mass)
Graham’s Law of Effusion • Effusion is the escape of a gas through a tiny hole (a balloon will deflate over time due to effusion).
Diffusion • The spread of gas through space. After watching the video on Bromine answer the following questions: Why does the gas diffuse? Why does it take more time than you would expect?
Diffusion • The spread of gas through space. After watching the video on Bromine answer the following questions: Why does the gas diffuse? - random motion of the molecules Why does it take more time than you would expect? - they are moving very fast, but collide with the air molecules
Which will effuse faster: CH4 or Xe ? • Explain why a a gas will diffuse faster in hot air than cold air?