Breathing in and out

Prior Knowledge: Students should have a basic understanding of the structure of the respiratory system such as lungs, diaphragm, trachea, mouth and nose. The students should also have a general understanding of structures and function of other body systems.

Lesson Objective: By the end of today’s class, SWBAT describe the basic function of the respiratory system.

Basic Description of Assignment: This lesson is designed to allow the students to be able to see and feel the function of the respiratory system. This short lab allows the students to examine how the human body takes in its needs and expels wastes. The student will be taking a regular daily activity, breathing, which most often not thought about and be able to manipulate and explain its functions.


– clean window


Step 1: Student breathe in deeply and exhale two times

Step 2: Time how long student can hold their breath and ask them why they cannot hold their breath forever

Step 3: Ask student what they think they are breathing in and what they are breathing out. Explain why

Step 4: Have student hold their hands in front of them and exhale into hands for 30 seconds

Step 5: Student describes what came out onto their mouths and hands and why

Step 6: Student exhales in front of a mirror for 15 seconds and describe what is on the window

Step 7: Ask student to explain what we breathe in and what we breathe out and why.


Reasoning behind Lesson:

The purpose of this lesson, like all of the other lessons is to guide the student to inquire and draw their own conclusions. This lesson draws attention to a phenomenon that the student should already be familiar with which is breathing. Most students at this age understand that we need oxygen to breathe, but don’t necessarily understand why we need to exhale. This lesson demonstrates that we don’t just exhale gases, but also water particles as demonstrated by the moist hands and fogged up window. This lesson is based on a lot of observations and guiding questions that should help the student to be able to come up with the conclusion that oxygen goes in and carbon dioxide and water comes out.

A common misconception is that humans only breathe out carbon dioxide. While this may be partially true, it is equally as important to point out to students that water is also byproduct of exhalation. The conclusion that the student should draw using the connections between what they have observed and perceived from before is that we need oxygen to live, but carbon dioxide and water are considered as wastes and can be harmful in this particular system. This lesson really pushes students to make connections between guiding questions and observations to be able to draw intuitive conclusions.




This lesson is fairly simple, but requires a lot of critical thinking. Some students may not have the background knowledge that would enable to understand the concept of inhaling in oxygen and exhaling carbon dioxide. In this case, students without the vocabulary should be able to understand the basic concept that respiration takes in something we need and gets rid of something that we do not need by exhalation. In this case, we can ask why do we breathe in and why do we breathe out? Asking guiding questions such as is this a good thing for our body system or bad thing will propel our students to start thinking about the body systems as self-maintaining.

For students who understand the concepts quickly, you can starting asking more probing questions such as why do we breathe more heavily when we run than when we are walking? These higher tiered questions will help our students to think about and apply what they have learned in a different context. Other higher order questions could be, “why can’t we breathe underwater?” This has launched many conversations in my classroom about what can take into our lungs and what we cannot.  Another question to ask is why it is bad to smoke? How does this affect our respiratory system.


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