Chemistry II AP Objectives

Links:

College Board Topic II:
States of Matter

Topics:

1. Gases
   1. Laws of ideal gases
      1. Equation of state for an ideal gas
      2. Partial pressures
   2. Kinetic-molecular theory
      1. Interpretation of ideal gas laws on the basis of this theory
      2. Avogadro's hypothesis and the mole concept
      3. Dependence of kinetic energy of molecules on temperature
      4. Deviations from ideal gas laws

Time Range:
See course calendar

Suggested Teaching Strategies:
1. a. Open unit with Alka Seltzer rocket; ask students to describe what happened and why. Let their answers lead into a discussion of Boyles Law. Draw attention to how their observations led to theories about how gases behave. Use this lead in to cover other gas behaviors i.e. Charles Law and Avagadro's Law. Reinforce Boyles' Law and Charles Law with Popcorn lab from the Chem Sourcebook CD Rom and the Charles Law lab from the Addison Wesley lab handbook. Show how these laws can be mathematically related to form the Ideal Gas Law.

1. b. The concept of partial pressure is presented to the students through a pair of demonstrations. The first shows that water can be condensed from the vapor space above warm water. The second shows that light hydrocarbons such as acetone can be evaporated using a aspirator to lower the partial pressure in a container's vapor space.

2. a. Reintroduce idea that pressure represents force applied per unit of area, tie idea of force to molecular collisions with container wall, use demonstration to reinforce such as popper toy, popcorn popper or Jiffy pop popcorn. Use Brown and LeMay CD to demo the effect of increasing temperature on molecular speed and frequency of collisions. CD demo can also be used to tie in effect of increased number of molecules on KMT gas properties. Work through additional examples until students are confident that KMT "makes sense", that the results of any system change can be predicted.

2. b. Previously covered in II. A. 1. a.

2. c. Previously covered in II. A. 2. a.

2. d. Use understanding of KMT to predict the conditions where molecules will be least likely to behave ideally. Show how Van der Waals equation makes adjustments for these conditions.

Aligned Resources:

• Former Core lab - Molar Mass of a Gas
• Brown and LeMay CD

Revision Date:
May 2001