Lesson 4: Real Gases and Deviations from Ideal Behavior

What assumptions are made in the Ideal Gas Law that are not always true for real gases?

How do intermolecular forces affect the pressure and volume of a real gas?

How does the size of gas molecules affect the volume occupied by a real gas?

Under what conditions do real gases behave most like ideal gases, and when do they deviate significantly?

How does the van der Waals equation attempt to correct for the non-ideal behavior of real gases?

Real Gas

Ideal Gas

Intermolecular Forces

van der Waals Forces

Molecular Volume

Compressibility Factor (Z)

van der Waals Equation

Deviation

High Pressure

Low Temperature

NGSS HS-PS1-3: Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles. (Connecting non-ideal gas behavior to intermolecular forces).

NGSS HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects).

Critical thinking and analysis of scientific models.

Interpretation of graphs and data.

Understanding of the limitations of scientific laws.

Application of scientific reasoning to explain complex phenomena.

Description
Students will learn about the behavior of real gases and how they deviate from the assumptions of the Ideal Gas Law. They will explore the effects of intermolecular forces and molecular volume on gas properties. The lesson will also introduce the van der Waals equation as a model for real gas behavior.

Purpose
To provide a more complete and nuanced understanding of gas behavior, recognizing the limitations of the Ideal Gas Law and introducing factors that influence real gas behavior.

DOK Level
DOK 1: Define real gas, intermolecular forces, and van der Waals equation.

DOK 2: Explain why real gases deviate from ideal behavior. Interpret graphs showing deviations.

DOK 3: Relate intermolecular forces and molecular volume to observed gas properties. Analyze the conditions under which deviations are most significant.

Discuss the importance of considering real gas behavior in industrial processes involving high pressures or low temperatures (e.g., ammonia synthesis, natural gas liquefaction).

Explore the use of real gas models in atmospheric science to understand the behavior of gases in the Earth's atmosphere.

Connect the concepts to the development of new materials and technologies that require precise control over gas properties.

Thinking that all gases always follow the Ideal Gas Law.

Underestimating the importance of intermolecular forces in determining gas behavior.

Assuming that the volume of gas molecules is negligible under all conditions.

Difficulty understanding the van der Waals equation and its parameters.

For struggling learners: Provide simplified explanations of intermolecular forces and molecular volume. Use visual aids to illustrate the concepts. Focus on qualitative understanding rather than complex calculations.

For advanced learners: Challenge them to research and present on specific applications of real gas models in engineering or scientific research. Have them explore the mathematical details of the van der Waals equation.

Visual Learners: Utilize graphs and diagrams illustrating gas behavior and deviations from ideality.

Kinesthetic Learners: Design a simulation where students model the interactions between gas molecules.

Formative:

Class participation in discussions and problem-solving exercises.

Completion of worksheets with conceptual questions about real gases.

Exit tickets asking students to explain why real gases deviate from ideal behavior.

Summative:

Quiz on real gas concepts.

Written assignment analyzing a case study involving real gas behavior.

Presentation on a real-world application of real gas models.

Textbook (e.g., Chemistry HMH)

Whiteboard or projector

Markers or pens

Worksheets with conceptual questions and problems

Computer with internet access

Online simulations (if available)

Scientific articles or case studies on real gas applications

Graphing software (optional)