Creating a Positive Learning Environment for Everyone Be respectful of your classmates Save conversation for clicker portions of lecture Put cell phones in “airplane” mode Turn off tablets Close laptops

Chemistry Joke of the Day Did you hear about the man who cooled to absolute zero? He’s “0 K” now…

Announcements Exam #1: Tuesday, September 26th, 7:00-8:30pm, locations on website Q&A Review Sessions on website Ti-Nspire calculator NOT allowed during exam Conflict Exam: 5:00-6:30pm, 161 Noyes Lab, sign up in 1026 Chemistry Annex until noon on 9/26 Review Questions for Exam 1 due tomorrow by 5:00pm Practice/old exams posted on website

Clicker #1 Can Crushing Demonstration The can crushes when put in cold water because… The temperature of the gas in the can drops so the pressure in the can drops below atmospheric pressure helping to crush it. Some of the moles of water vapor gas in the can become liquid water, so the pressure in the can drops below atmospheric pressure helping to crush it. The volume of gas in the can went down so the pressure of the gas went up above atmospheric pressure, helping to crush it. All of the above (A-C) Two of the above (A-B)

Kinetic Molecular Theory Gases are made of particles in constant random motion. Temperature is a measure of random kinetic energy. Pressure is due to collisions of gas particles with the container.

KMT (assumptions) Assume the volume of the gas particles is negligible (zero). Assume that gas particles exert no attractive forces (elastic collisions).

Clicker #2 The two balloons above are the same size but contain different gases. How do the pressures inside the balloons compare? A) The pressures are the same. B) The balloon with helium (He) has the greater pressure. C) The balloon with xenon (Xe) has the greater pressure. D) Not enough information is given to answer this question. He Xe

Kinetic Energy – Proportional to Temperature High mass low velocity Low Mass High Velocity Same temperature – same average kinetic energy

Clicker #3 The two balloons above are the same size but contain different gases. Which gas particles will hit the walls of the balloon harder? A) They both hit with the same amount of force. B) The helium particles will hit harder. C) The xenon particles will hit harder. He Xe

Clicker #4 You are holding three balloons each containing the same mass of gas. One balloon contains hydrogen gas, one contains helium, and one contains oxygen. Which balloon is the largest? A) The hydrogen balloon is the largest. B) The helium balloon is the largest. C) The oxygen balloon is the largest. D) All of the balloons are the same size.

Clicker #5 A 50.0-L steel tank contains 186 mol N2 and 145 mol O2 at 24oC. What is the partial pressure of each gas in the tank? What is the total pressure in the tank? Before doing this problem, which gas do you expect to have a greater partial pressure? A) Nitrogen gas B) Oxygen gas gas C) Both gases have the same partial pressure