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#### Full of Air

Purpose:As a result of this activity, students will be able to have a better understanding of the usefulness of Avogadro’s hypothesis.
Related Standard & Benchmarks:
 Science Standard 8. Understands the structure and properties of matter Level IV [Grade 9-12] Benchmark 13. Understands the complete mole concept and ways in which it can be used (e.g., actual mass vs. relative mass; relationship between the mole and the volume of a mole of molecules; relevance of molar volume and Avogadro’s hypothesis)
 Mathematics Standard 3. Uses basic and advanced procedures while performing the processes of computation Level IV [Grade 9-12] Benchmark 1. Adds, subtracts, multiplies, divides, and simplifies rational expressions
 Mathematics Standard 4. Understands and applies basic and advanced properties of the concepts of measurement Level IV [Grade 9-12] Benchmark 3. Selects and uses an appropriate direct or indirect method of measurement in a given situation (e.g., uses properties of similar triangles to measure indirectly the height of an inaccessible object)
 Mathematics Standard 4. Understands and applies basic and advanced properties of the concepts of measurement Level IV [Grade 9-12] Benchmark 5. Uses unit analysis to solve problems involving measurement and unit conversion (e.g., between metric and U.S. customary systems, foreign currency conversions)
Student Product:Calculations showing number of molecules in selected container
Material & Resources:Containers, calculator, ruler or meter/yardstick, writing materials, periodic table of the elements, reference books
Teacher's Note:This activity could be extended by using the gas laws to adjust for the differences of temperature and atmospheric pressure from the standard temperature and pressure.
Activity
Each student or small group will have a container. This can be a jar, shoebox, or other common household or school container. Each student or group will determine the volume (in liters) of air in their container, using appropriate measurement techniques, formulas, and estimation. Students will then calculate how much of the volume is represented by the various gases that make up the atmosphere. Depending on the level of complexity desired, students may be asked to look up the percentage of composition for all gases, or only the major components of the atmosphere (i.e., Nitrogen, Oxygen, Argon). For example, the amount of a gas that comprises 75 percent of the atmosphere in a 2 liter volume would be 1.5 liters (.75 X 2 liters = 1.5 liters). Once the volumes have been calculated, students are ready to calculate the approximate number of molecules of each gas, by using Avogadro’s relationship that one mole of particles (6.02 X 1023) has a volume of 22.4 liters at standard temperature and pressure. Students should list the number of molecules of each gas, and the total number of molecules present. As an extension activity, students could be asked to calculate the mass of molecules present using the relationship that the mass of one mole is equal to the atomic mass of one molecule.