Modeling Photosynthesis and Cellular Respiration

Biology Developing and Using Models Fifth Grade Grade Level High School Middle School Uncategorized

In January, I did the Modeling Photosynthesis and Cellular Respiration activity created by the California Academy of Sciences.   For the full activity, visit their website here.

I first saw this activity demonstrated at the California Science Teachers Association Conference back in October.  Students use ping bong balls to represent atoms and egg cartons to hold the atoms together to create molecules.  This kinesthetic model is a great way to demonstrate conservation of matter, photosynthesis and cellular respiration.


Each group will need:

  • 6 egg cartons
  • 36 ping-pong balls (FYI, beer pong balls are cheaper.  I used these plain white ones.)
  • energy tokens
  • signage of your choice

There is a full explanation of how to create the pieces you need in the pdf document for this activity.

You will cut and combine the egg cartons to create holders for the ping pong balls.   In all honesty, this can be a logistical nightmare.  However, the setup can be used year after year.  Also, this is a great activity for a TA or student helper.


The Activity

Stoma sign on the door out of my classroom.Students will bring in carbon dioxide molecules in through the stoma (your door) and water molecules through the stem (your sink).  They will use these to build glucose molecules.

I added signs to the doors in my classroom labeled “stoma” and placed the carbon dioxide molecules in a medium sized storage container on a desk outside of the classroom.

I placed another medium sized storage container near the sink in the back of my classroom.  The tables were pushed near the sink to direct traffic and also represent a stem.

Two tables covered in a green tablecloth, each labeled stem. There is a sink in the background.

Students are allowed to collect one “molecule” at a time.  They cannot go and get another molecule until each “atom” has been placed in the glucose storage container (egg carton).  They also cannot place an atoms in the glucose container without using an energy storage token.  I just used orange card stock cut into squares.  The energy tokens must be placed under the ping-pong balls as they are added to the glucose molecule.  This represents stored energy.

Eventually, students will end up with too much oxygen but they will still need carbon and hydrogen atoms.

At that point I took out another container that full of oxygen egg cartons.  Students were allowed to use them to take oxygen molecules back out through the stoma.  Students can continue to collect water and carbon dioxide and use it to build glucose while getting rid of excess oxygen.

In order to model cellular respiration, students would do the the opposite process.  They would be left with carbon dioxide, water and energy tokens (useable energy).

Tips for Success

  • Start collecting egg cartons early.

I started at the end of October and ended up not having as many as I would have liked by the time we did this activity in January.  I recommend posting something in your school newsletter or posting a request on a local Facebook group.

We ended up having a bunch of people bring in cartons after the fact so I have plenty for next year, but the supplies we had forced me to have students work in groups of 6.  This wasn’t ideal.  That brings me to my next tip.

  • Work in smaller groups.

The instructions say that students can work in groups of 4-6.  In my opinion, that is far too many students in one group.  I find that in larger groups some students have a tendency to expect that someone else will do the work for them.  In smaller groups there is more work to do and no one is able to slack.  I would recommend groups of 3-4, but this also means that you need more egg cartons.


We tried to prevent this problem by having very specific jobs.  Students were given name tags with their job titles and instructions on the back.  Everyone in the class had something they were responsible for.

It was still pretty chaotic and students had trouble understanding the expectations.

  • Follow up each process with a reading activity.

Some students will totally understand these concepts right away.  Other students will struggle with explaining what happened.  This is an excellent place to provide them with something to read to help them fully understand these concepts.  Those old textbooks that you have gathering dust in the back of the classroom will totally do the trick.

  • Use an alternate to ping-pong balls. (Perhaps)

Ping pong balls are super exciting for a class of middle school kids.  It was really hard for them to not bounce them around the classroom.  They did pretty well, but it was hard to manage.

I talked about this frustration at a district collaboration.  Another teacher mentioned that she did the same activity but used different size pom poms in place of the ping-pong balls.  She used small pom poms to represent the hydrogen atoms, and larger pom poms to represent larger carbon and oxygen atoms.

This added a lot of extra expense, but it also helped her to further demonstrate the law of conservation of mass and the differences in atom size.

  • Designate a place for students to keep their empty carbon dioxide and water molecules at their table.  

If students keep their cartons at their tables, it will allow them to see that it takes 6 carbon dioxide molecules and 6 water molecules to build one glucose molecule.  This also helps them to further understand the law of conservation of mass.

I didn’t designate a spot, so these pieces ended up all over the place.  They returned them to the storage container and put them on random tables.  Next time I do this activity, I will provide them with a set location to help with this problem.

  • Plan for storage ahead of time.  

There is a lot of material that you will be working with .  Luckily, the egg cartons can be stacked together and the ping-pong balls can be kept in a storage container or large ziploc bag.  Once you are done, it won’t take up a ton of space.

Storage containers with blue dry erase tape.

However, before the start of the activity, I put each “molecule” type in a different storage container and used dry erase tape on the outside.   This allowed me to build the molecules and have them set up for class time.  I also shared this activity with another teacher and this helped keep it organized between the classrooms.

NGSS Alignment

  • Fifth Grade
    • This activity aligns with 5-LS1-1 and 5-PS3-1.  However, I think this would be a lot to manage logistically in most fifth grade classrooms.  I think this would be a good idea to use as a demonstration.
  • Middle School
    • This activity aligns with MS-LS1-6 , MS-LS1-7  and MS-PS1-5.  I think this is a fantastic resource to use in a middle school classroom, but look at the recommendations above.
  • High School
    • This activity aligns with HS-LS1-5 and could be adapted to strongly align with HS-PS1-7. Students could calculate the molecular mass for each atom in order practice this standard.

For more modeling activities, click here.

*This post is not endorsed or associated in any way with the California Academy of Sciences.






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3 thoughts on “Modeling Photosynthesis and Cellular Respiration”

  1. Great idea! I’m debating doing the activity. If you use groups of 4, what other than the CO2, water, and energy collector, would be your 4th job? Oxygen collector? Di you have the students fill out something during the activity?



    1. I didn’t have students fill anything out last time, because I wanted them to be more engaged in the lesson. However, when I do it this year, they will definitely have something to fill out. I am not sure what exactly, but I’d be happy to trouble shoot that with you. Maybe some kind of doodle notes that were pre-outlined for them?

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