GT 3 Kinetic Moleculat Theory, Ideal Gas Law, Graham’s Law, Daltons Law of Partial Pressures

Evaluation/Assessment: Objective: Today I will be able to: Construct an explanation for why a can collapses under different temperatures Apply the kinetic molecular theory to solving Ideal Gas Law and Graham’s Law problems Evaluation/Assessment: Informal Assessment – Monitoring student progress and questions as the students complete the practice worksheets Formal Assessment – Analyzing student responses to the practice worksheets and the exit ticket Common Core Connection Make sense of problem and persevere in solving them Look for and express regularity in repeated reasoning

Lesson Sequence Evaluate: Warm – Up Engage and Explore: Collapsing Can Demo Explain: Ideal Gas Law Elaborate: Ideal Gas Law Practice Explain: Grahams Law Elaborate: Grahams Law Practice Evaluate: Exit Ticket

Warm - Up List the constant variables in the following gas laws Boyle’s Law Charles’ Law Gay-Lussac’s Law What is STP?

Objective Today I will be able to: Construct an explanation for why a can collapses under different temperatures Apply the kinetic molecular theory to solving Ideal Gas Law and Graham’s Law problems

Homework Finish Classwork Gases Exam Thursday, March 27

Agenda Warm – Up Collapsing Can Demo Ideal Gas Law Notes Ideal Gas Law Practice Grahams Law Notes Grahams Law Practice Exit Ticket

Collapsing Can Demo Watch Ms. Ose’s Demonstration With a group construct an explanation for what is occurring inside the can (5 minutes) Share the explanation with the class

Kinetic Molecular Theory, Ideal Gas Law

Kinetic Molecular Theory of Gases Gases consist of small particles, either atoms or molecules, that have mass Gas particles must be separated from each other by relatively large distances - While gases do have volume, that volume is considered to be zero, which is why we say the volume of a gases’ container is the volume of the gas

Kinetic Molecular Theory of Gases Gas particles must be in constant, straight-line, rapid motion - Explains why when you spray a bottle of perfume at one end of the room, the people at the other end are able to smell it right away - Gases diffuse rapidly

Kinetic Molecular Theory of Gases Gases exert pressure because their particles collide with the walls of the container -Think about blowing up a balloon – the balloon blows up evenly because gas particles are hitting all points of the inside walls the same

Kinetic Molecular Theory of Gases Gas particles exert no force on one another – they neither attract or repel - It is true enough for our class

Kinetic Molecular Theory of Gases Gas particles may collide with each other, but these collisions are assumed to be elastic - Think about playing pool – you transfer kinetic energy from your stick to the cue ball to make it move

Elastic vs. Inelastic Collisions POW 8 v1 v2 elastic collision v3 v4 8 inelastic collision

Kinetic Molecular Theory of Gases The average kinetic energy of the gas particles depends on the temperature of the gas - Gas particles do not all have the same kinetic energy – some move slowly and some move very fast, but most are in between - Explains why snow can evaporate when it is so cold outside

Kinetic Molecular Theory of Gases A gas that obeys all these “rules” is called an Ideal Gas No gas will obey all the “rules,” but some are close enough Nonpolar gases at high temperatures and low pressure are very close

Ideal Gas Law PV = nRT P = pressure V = volume (use only L) n = number of moles of gas R = constant (.0821 atm-L/mol-K or 62.4 mmHg- L/mol-K) T = temperature in Kelvin

Ideal Gas Law Practice Complete the practice at your desk. If you have questions please ask Ms. Ose. We will review selected problems

Grahams Law

Graham’s Law The rates of diffusion of gases at the same temperature and pressure are inversely proportional to the square roots of their molar masses Normal language: lighter gases move through the air faster than heavier gases Example: helium moves faster than radon

Graham’s Law Diffusion – particle movement from an area of high  low concentration Effusion – diffusion of gas particles through an opening NET MOVEMENT NET MOVEMENT

Graham’s Law Rate = rate of diffusion or effusion – usually measured in distance/time (m/s) M = molar mass

Graham’s Law On average, carbon dioxide travels at 410.0 m/s at 25.0˚C. Find the average speed of chlorine gas at 25.0˚C. Hint: put the lighter gas in the numerator = 323 m/s

Grahams Law Practice Complete the practice at your desk. If you have questions, please ask Ms. Ose. We will review selected problems

Dalton’s Law

Dalton’s Law of Partial Pressures The sum of the pressures of all gases present in a system equals the total pressure of the system P1 + P2 + P3 + … = Pt

Dalton’s Law Practice Complete the practice at your desk. If you have questions, please ask Ms. Ose. We will review selected problems

Exit Ticket Imagine that you are going on an airplane trip in an unpressurized plane. You are bringing aboard an air-filled pillow that you have inflated fully. Predict what will happen when you try to use the pillow while the plane is at cruising altitude.