Lesson:  What a Gas


Kaylan Duthie

Unit Theme/Course:

Human Respiration – 7th Grade Life Science


November 30th-31st


1.5 days



·         Students will draw upon a previous lab during the digestions unit where they investigated diffusion, and this time learn about diffusion of gas through a membrane

·         Problem:  How does CO2 get past the membranes in our body?



Students will determine whether carbon dioxide can pass through a membrane through an activity that will provide evidence.  They will pour carbonated water into a membrane and place in bromothymol blue solution.  They will find that the carbon dioxide will diffuse through the membrane, demonstrated by a color change in the test tube outside of the membrane.  In the body, oxygen and carbon dioxide are exchanged as blood circulates, and it is important that gases be able to easily cross membranes.


Learning Objectives

[cognitive, academic, language, socio-cultural]

Assessment Criteria

Students can explain how gas moves across a membrane

Gas (carbon dioxide) diffuses from the alveoli to the capillary

Student can trace the pathway of carbon dioxide exiting the body

Carbon dioxide diffuses from the capillary to the aveoli, then passes out through the trachea, and then exits through the nose or mouth.



6-8 SYSA

Any system may be thought of as containing subsystems and as being a subsystem of a larger system.

Given a system, identify subsystems and a larger encompassing system (e.g., the heart is a system made up of tissues and cells, and is part of the larger circulatory system).

6-8 LS1C

Multicellular organisms have specialized cells that perform different functions. These cells join together to form tissues that give organs their structure and enable the organs to perform specialized functions within organ systems.

Relate the structure of a specialized cell (e.g., nerve and muscle cells) to the function that the cell performs.


Explain the relationship between tissues that make up individual organs and the functions the organ performs (e.g., valves in the heart control blood flow, air sacs in the lungs maximize surface area for transfer of gases).


Describe the components and functions of the digestive, circulatory, and respiratory systems in humans and how these systems interact.

6-8 INQA


Scientific inquiry involves asking and answering questions and comparing the answer with what scientists already know about the world.

Generate a question that can be answered through scientific investigation. This may involve refining or refocusing a broad and ill-defined question.


6-8 INQB


Different kinds of questions suggest different kinds of scientific investigations.

Plan and conduct a scientific investigation (e.g., field study, systematic observation, controlled experiment, model, or simulation) that is appropriate for the question being asked.


Propose a hypothesis, give a reason for the hypothesis, and explain how the planned investigation will test the hypothesis.


Work collaboratively with other students to carry out the investigations.



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