Lesson 4.2 Behavior of Gases
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C HAPTER
Chapter 1. Lesson 4.2 Behavior of Gases
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Lesson 4.2 Behavior of Gases
Key Concept Particles of a gas are constantly moving and colliding with other things, giving the gas pressure. The gas laws describe the relationships among pressure, volume, and temperature of a given amount of gas.
Standards • SCI.CA.8.IE.9.g • NSES.5-8.G.3.2 • AAAS.6-8.1.A.4; AAAS.6-8.1.C.1; AAAS.6-8.4.D.5; AAAS.6-8.9.B.3; AAAS.6-8.12.D.1, 4
Lesson Objectives • Define pressure. • State the gas laws.
Lesson Vocabulary • Amonton’s law: gas law stating that, if the volume of a gas is held constant, increasing the temperature of the gas increases its pressure • Boyle’s law: gas law stating that, if the temperature of a gas is held constant, increasing the volume of the gas decreases its pressure • Charles’s law: gas law stating that, if the pressure of a gas is held constant, increasing its temperature increases its volume • pressure: gas law stating that, if the pressure of a gas is held constant, increasing its temperature increases its volume
Teaching Strategies Introducing the Lesson
Ask students to recall from Lesson 4.1 the properties of matter in the gaseous state. (Gases have neither a fixed volume nor a fixed shape. Instead, they take both the volume and shape of their container.) Tell the class that the ability of gases to fill their containers gives them some interesting behaviors, which they will learn about in this lesson. 1
www.ck12.org Discussion
Discuss the imaginative analogy at the URL below (of monkeys randomly throwing tennis balls in a room). The analogy may help students understand why gases have pressure and how variables such as temperature are related to gas pressure. • http://www.geocities.com/CapeCanaveral/7639/atmosphere/heatnpressure.htm Demonstration
Demonstrate the pressure that air exerts with the century-old “egg-in-a-bottle” experiment. Complete instructions, as well as an entertaining video demonstration, can be found at this URL: http://www.stevespanglerscience.com/ experiment/egg-in-bottle . Building Science Skills
At the start of class, while students watch, fully inflate and tie off a balloon. Then place the balloon in an ice chest or refrigerator. Ask students to predict how the balloon might be different after it cools. At the end of class, bring out the balloon, which should be noticeably smaller, and challenge students to explain why. Differentiated Instruction
Tell students to make a main ideas/details chart for the lesson. Before they read, they should write the main headings from the lesson on the left side of a sheet of paper, leaving space between them for details. Then, as they read the lesson, students should fill in details on the right side of the chart Enrichment
Ask a few interested students to research the three scientists who discovered the gas laws: Robert Boyle, Jacques Charles, and Guillaume Amontons. Tell them to a write a short, illustrated profile of each scientist that includes how he discovered the gas law that bears his name. Make the profiles available to the rest of the class, and encourage other students to read them. Science Inquiry
Have pairs of students explore the gas properties of volume, temperature, and pressure with the simulation at the URL below. They should hold one of the three properties constant, vary one of the other two properties, and observe how the third property changes. For example, while holding volume constant, they can vary temperature and see how pressure changes. They should repeat this process until they have investigated each pair of properties. Tell students to create data tables to record several values for each pair of properties. Then have them graph the data and identify which gas law each graph represents. • http://phet.colorado.edu/en/simulation/gas-properties Real-World Connection
Relate the behavior of gases to students’ daily lives. Explain how air pressure is needed to blow up balloons, inflate tires, flush toilets, drink through straws, play musical instruments, and even breathe. 2
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Chapter 1. Lesson 4.2 Behavior of Gases
Reinforce and Review Lesson Worksheets
Copy and distribute the Lesson 4.2 worksheets in CK-12 Physical Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content. Lesson Review Questions
Have students answer the Review Questions at the end of Lesson 1.1 in CK-12 Physical Science for Middle School FlexBook® resource. The answer keys can be found in the Resource tab above the Table of Contents. Lesson Quiz
Check students’ mastery of the lesson with Lesson 4.2 Quiz in CK-12 Physical Science for Middle School Quizzes and Tests.
Points to Consider In this lesson, you read that heating a gas gives its particles more kinetic energy. As a result, its volume or pressure also increases. The opposite happens when a gas is cooled. What might happen if you cool a gas to an even lower temperature? Might it change state and become a liquid? Can you predict the role of energy in changes of state?
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