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Volume of Pressurized Gases

Name of Corresponding Unit Plan: Archaeological Documentation

Grade Level: 9-12

Common Core Standards:
RS9-10. 3. Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text.

M 7.G.6. Solve real-world and mathematical problems involving area, volume and surface area of two- and three-dimensional objects composed of triangles, quadrilaterals, polygons, cubes, and right prisms.

M 8.G.9. Know the formulas for the volumes of cones, cylinders, and spheres and use them to solve real-world and mathematical problems.

Content Areas: Math, Science

Recommended Length/Duration: 45-60 minute period

Learning Goals: Students will learn to calculate the volume of pressurized gas using Boyle’s Law.

Description/Sequence:

  1. Discuss the definition of volume.  While gases conform to the shape of their container, the space they fill can be very large.  One way to put a large amount of gas into a small space is by compressing it and storing it under pressure.
  2. Discuss various gases that are typically under pressure (e.g. bicycle tires, balloons, propane gas, aerosol cans) The volume of the gas is greater than the volume of the container.
  3. 3.  Discuss how pressure is measured.  Define some of the common units (e.g. atmosphere, psi, bars).
  4. Introduce Boyle’s Law.  Point out that Boyle’s Law is a theoretical relationship and that actual gases under pressure behave with slight variations.
  5. Use the Black/White board to do an example of the volume of gas that can be held in given size container at a given pressure. 
  6. Discuss Boyle’s Law which states that the pressure exerted by a gas held at a constant temperature varies inversely with the volume of the gas. For example, if the volume is halved, the pressure is doubled; and if the volume is doubled, the pressure is halved.  Point out that Boyle's Law actually applies only to an ideal, theoretical gas. When real gases are compressed at a constant temperature, changes in the relationship between pressure and volume occur. However, the law is accurate enough to be useful in a number of practical applications.
  7. Work some examples of how to calculate the volume and pressure of the gas in given sized tanks. 
  8. Have students work the examples on worksheet.
  9. Once students have had a chance to do the calculations, compare findings and clarify any errors or questions.

Assessments: Check worksheets for accuracy.

Materials/Resources: Worksheets, Calculators

Special Considerations: Weaker math students could be partnered with stronger students.

Scientific measurements are generally easier to take and calculate in metric than in English units.  Additional work may be needed if students are not familiar with metric measurements, or if the teacher chooses to use English units.

Extensions:
Boyle’s Law is important for SCUBA divers in planning their dives.  Students may want to research other occupations or activities that require knowledge of pressurized gasses.