One of the core tenets of the OmniLearn method is that nearly all lab activities can be up leveled or down leveled to meet just about any age. When you are searching for activities to bring to your classroom don’t be afraid to widen the age bracket! With a little creativity and age appropriate language and safety practices, just about any experiment can be carried out from PreK to 12th grade!
In this series, we give examples on how we have taken high level science (often high school level labs) and brought them down for middle schoolers, elementary schoolers and even PreKers. Or the reverse! We take a simple activity and do a deep dive into the science.
CO2 and Exercise
The basic lab premise: When we move our bodies, our cells increase the amount of cellular respiration in order to create the energy to move around. A byproduct of cellular respiration is carbon dioxide. The more you exercise, the more carbon dioxide your body makes. Bromothymol blue (BTB) is a pH indicator. In a neutral solution, BTB is green and in an acidic solution BTB turns yellow. When you add carbon dioxide to water it forms carbonic acid (H2CO3). In this lab students exercise for 0, 1, and 2 minutes and then exhale into a water/BTB solution to qualitatively assess their carbon dioxide output.
Safety
The main safety concern with this lab is the use of BTB. This chemical should not be ingested. This lab has students blowing bubbles into the cups using a straw. Students after putting straws into their cups tend to ask “what happens if I accidentally drink it?”. I suggest jokingly to classes that only students that know the difference between breathing in and out should be selected as test subjects. Students from high school to upper elementary are able to confidently make this distinction. It’s important to make it clear that students are blowing gas through the straw slowly. They should be forming gentle bubbles in the liquid, rather than rapid large bubbles. Test subjects can wear safety glasses to ensure that none of the BTB water splashes into their eyes as a precaution.
High School
At a high school level students are learning about homeostasis as well as the function and interaction of different body systems and the ability of body systems to work together to maintain homeostasis. Students should easily be able to use vocabulary such as homeostasis, O2, CO2, respiratory system, circulatory system, and cellular respiration. Students quantitatively measure their heart rate at each exercise interval and accurately measure the time it takes for their BTB solution to turn yellow with a steady exhale. Students should accurately measure the regents to make their BTB solutions using a graduated cylinder and reading written instructions. They should have a basic understanding of pH and the terms acid, base, and neutral. Students should only need a minimal reminder that there is no food or drinks allowed during lab time.
Middle School
At a middle school level, the lab covers body systems involved in exercise and the process that cells go through to convert oxygen to carbon dioxide. Students use words like carbon dioxide, lungs, inhale, exhale, oxygen, pH, indicator, heart, circulatory system, respiratory system, and heart rate (BPM). The procedure is similar to high school with the possibility of simplifying it to either exclude heart rate measurements from data collection or only have one test subject per group. Students will measure the identical amount of water and BTB for each cup. This offers an opportunity to discuss constants in an experiment and the reason behind them. After collecting data, it’s important at this level to discuss as a class what a shorter and longer color change time tells us about the amount of CO2 produced as this might not be clear to all students. Also if pH has been covered, this is a prime time to discuss why BTB changes color.
Upper Elementary
At an upper elementary level (3-5), students still learn about the human body and the change from oxygen to carbon dioxide in less complex terms. The same vocabulary is covered as middle school with the exception of corresponding body systems and heart rate (BPM). The procedure is primarily the same except that students will only take coloring changing time data. The other difference is that we will go through the procedure as a class so that everyone is on the same step. It is expected to see more fluctuations in data collection so it’s helpful to complete the multistep procedure as a class. The connection between the color change time and carbon dioxide amount won’t be intuitive to students and will be given to students (longer time = less carbon dioxide, shorter time = more carbon dioxide).
Lower Elementary
At a lower elementary school level (K-2), the main change from upper elementary is safety focused. To avoid students from drinking the BTB liquids, students blow into the water cups prior to adding the BTB. We also switch from quantitative data to qualitative data. We start by talking with students about what happens when we exercise. Each student is given 4 cups with 50 mL of water already in each. BTB is also added by the teacher in this procedure to prevent data errors. In cup 1, we add BTB to the water to see what color it becomes. In cup 2, students blow bubbles while we count down from 5. Students dance around the room for a minute before blowing into cup 3 for 5 seconds. This is repeated a second time with students dancing for 2 minutes to a highly requested song. After each bubble blowing step, we add BTB to the cups for students to observe the color change from blue-green to yellow. Students observe that the longer they dance, the more breaths they take, and the more the color changes. Students can summarize their findings by coloring in the cup drawing to show what cups 1-4 looked like.
PreK
At a PreK level, the BTB can be replaced with red cabbage juice. This ensures there aren’t any safety concerns with students drinking the colored liquids. You will need to test the cabbage juice out though to ensure that the concentration added to the cup provides clear color changes between the cups.
Want more ideas on how to take a lab and modify it for your students?
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