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  • Writer's pictureKate McDaniel

Age is Just a Number: Liver

One of the core tenets of the OmniLearn method is that nearly all lab activities can be upleveled 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. 


Liver Lab: Catalase Enzymatic Reaction


The basic lab premise: there is a high concentration of the enzyme catalase found in beef liver (also in our liver). Catalase will break apart hydrogen peroxide and turn it into water and oxygen gas. If you drop a chunk of liver into a cup of hydrogen peroxide, it will fizz and bubble. It will also release some heat because this reaction is exothermic. At every age, we end the lab with a demonstration about how flammable pure oxygen is by lighting a popsicle stick on fire, gently blowing it out and then reigniting it in the oxygen bubbles. See the reaction in the video below!



Safety:

Water - no safety issue there.

Raw beef liver - while incredibly gross, some people do eat raw beef liver.

Hydrogen Peroxide - in large quantities it is harmful if swallowed, however people use it to brush their teeth (and spit out the excess) so any small “accidental” ingestion from say a kid touching the peroxide and then touching their mouths is not a problem. This makes it a safe material for young students to handle themselves. 

Fire - students at all ages are restricted from handling the flaming popsicle stick. This is a demo that instructors carry out at student tables.



High School

At a high school level students are learning about the function and structure of enzymes as catalysts of reactions. We use vocabulary like enzyme, substrate, active site, denature. Students see the chemical formula equation and review how to balance it. Students calculate the amounts of water and peroxide to make four specific dilutions of peroxide and investigate how the concentration of substrate affects the reaction. They use a graduated cylinder accurately and we can talk about what a meniscus is. We also give them an odd number to measure, such as 75mL, so it takes slightly more effort. They collect data by measuring the level of bubbles to the nearest tenth of a centimeter. 

Liver Lab Results: The 0% is just water which has no reaction with the liver. As the concentration of hydrogen peroxide increases you can observe and measure more and more oxygen gas bubbles.

Middle School

At a middle school level, we may leave the nitty gritty details of enzymes out of it and focus instead on the chemical reaction they are observing. The protocol is largely the same but this time they only test a 0%, a 50% and a 100% peroxide solution. We may also choose to give them the correct volumes of water and peroxide to use to make each solution or calculate the volumes as a class. They get more practice using graduated cylinders (with an approximate +/- 1mL error). They measure the level of bubbles to the nearest 0.25 of a centimeter. After seeing the reaction firsthand, they use molecular models to simulate the balanced reaction and figure out how to use all the parts of two hydrogen peroxide molecules to make a water molecule and two oxygen gas molecules. 


Upper Elementary

At an upper elementary level (3-5), we would omit the chemical formulas and review the reaction in plain english. During these years, students are starting to learn about body systems and the digestive system. Liver is a part of the digestive system. The liver's job is to break down toxins in the body. We relate this to students because if they have ever taken medicine or gotten a shot of novocaine at the dentist they know the effects wear off eventually. That is because the liver is doing its job. Our cells actually produce hydrogen peroxide as they make energy so our liver has the same enzymes as the cow to break down this harmful substance and turn it into two substances that are good for our bodies (water and oxygen). At this level, students will only test the liver in water and oxygen. But this provides an excellent opportunity to reinforce the importance of labeling and lab safety. We like to hold up unlabeled cups one containing water and one containing peroxide and ask students to determine which is which just by looking at it. How confident are they? So confident they would drink it? NO! This is a big reason why we never eat or drink anything in a lab, it could look safe but actually be dangerous. Students get more practice using graduated cylinders (with an approximate +/- 5 mL error). At this age, we might give them an even number to measure, such as 60, which is more obvious to find. They can measure the level of bubbles to the nearest 0.5 of a centimeter.


Lower Elementary

At a lower elementary school level (K-2) states of matter are the star of the show. Students still measure using a graduated cylinder. They will likely spill some and that's okay! Bring paper towels. This is fine motor development! The room for error is also bigger. Since the liver has no reaction in water and a big reaction in peroxide, it's not critical that they have the exact same volume. But when we tell young students they should be the same volume, it helps pave the path to talk about control variables. We still practice labeling. Maybe instead of using the full words as we would expect in grades 3-5 they use “W” for water and “P” for peroxide. We still review lab safety and how looks can be deceiving. At this age we also like to start labs by reviewing what senses scientists use to do labs. Ask students what the five senses are. “Do scientists use their sense of sight? Yeah!”. And then when you get to taste it's a big “NO! Scientists never ever put anything in their mouths!”. Students draw pictures of their cups after adding the liver. Second graders might even be able to label their drawings if given a word bank. We even see the bonus 4th state of matter, plasma, when we use the oxygen bubbles to ignite the ember on the popsicle stick. 



PreK

At a PreK level we might leave out states of matter all together and just focus on what is a chemist. A chemist is a type of scientist who mixes things together and looks at the reaction. We still do a big safety talk. When it comes to labeling we might spend more time on letter recognition and letter formation. We would write a big “W” on the board and ask students what letter it is and have them write it on one cup. And then repeat with the letter “P”. We can focus on number recognition. “What does the number fifty look like? It looks like a 5 followed by a 0. Can you find the number fifty on your graduated cylinder? Put your finger on the 50. Great job!”. We use a lot of repeats with new vocabulary. After introducing a tool like a graduated cylinder, have the class repeat it a couple times. When PreK kids are measuring the water and the peroxide it's really ok if it's not accurate at all. This is about fine motor skill development. When giving verbal instructions ALWAYS have them do the boring one first. They might get confused when you ask them what happened when they added the liver to the water. Because nothing happened. Students are sometimes afraid that “nothing” is not the correct response but it is absolutely a valid response in science. Sometimes nothing happens. This also helps create a build of excitement for when they add the liver to the peroxide. When we do the popsicle stick ignition demo, we relate the popsicle stick to a birthday candle. “What happens when you blow on your birthday candles? That's right they go out! Well look what happens when I put it into the bubbles!! It lights back up!”. And then go around the room and have each student blow out the popsicle stick and then reignite it in their bubbles. 





Download a version of the liver lab and try it with your students!


Bubbling Liver (K.1)
.pdf
Download PDF • 583KB

Liver Catalase Lab (7.2)
.pdf
Download PDF • 674KB

Liver Catalase Lab (LE.3)
.pdf
Download PDF • 593KB



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