Underwater Presidents

How many drops of water can a penny hold? We’re going to learn how to use the scientific method using everyday materials so you’re comfortable with how it works and how to apply it to every situations. Don’t worry – we’re also going to show you how to do more complicated projects later… but first, let’s cover the basics.

What you need: Pennies, eye or medicine dropper, water, a notebook or science journal.

Please login or register to read the rest of this content.


32 Responses to “Underwater Presidents”
  1. Aurora says:

    What a great question! Surface tension is basically the “film” created where a liquid and a gas meet. This film is impacted by different things, depending on both the liquid and the gas in question. We know that surface tension is changed by many factors, including oxidization, pressure, temperature, impurities, and various chemicals. Normally oxygen by itself would decrease surface tension, but the bubbles of carbon dioxide formed by carbonation create pressure, which does increase the surface tension

  2. Jeanette Spence says:

    We did this experiment with different kinds of liquids: testing the number of drops that the penny would hold of each water, grape juice, soapy water and sparkling smart water. My daugther’s data didn’t allow us to clearly come to any conclusions about the soapy water and the juice. Perhaps there were less drops with these two liquids. However it did look like the penny held more carbonated smart water. Does carbonation increase the surface tension of water and why? I can’t find anything online about this or at least anything that I can understand. Thanks for your help.

  3. Emily Crawford says:

    I told my cat my results and he was very confused.


    My son, who is anti-school, just completed this experiment and we watched the slowed down drops of water. THANK YOU THANK YOU THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!! He enjoyed it SOOOOOOOOO much!!! He’s coming up with his own experiments for us to do this week! You’ve blessed our socks off!!!!!!!!!!!!!

  5. Leslie Mann Damon says:

    We have used The Scientific Method as our daily class schedule for the past week and a half and that alone has been amazing! We have worked on vocabulary within the experiments, kept the journal, and done most all of the experiments. My kids are delighted and so am I. It is amazing to hear my daughter (9) talk about her observations and data collection! My 9 and 11 year kiddos are working well together and really enjoying this. I am thrilled at how well the text is presented so that I can teach this. My kids can’t wait for science class! Thank you for making me the best science mom on the block! I am really looking forward to starting in the curriculum next week. Thank you for this amazing program! It has been fun and educational in just the first week!…do you have one for math, grammar and history? 🙂

  6. Michelle Stevens says:

    I got 31 drops on the tails side and 42 drops on the heads side!!

  7. Adina Nelson says:

    My daughter is dictating and thinks this science experiment is really fun

  8. Kanatinia Ballard says:


  9. Aurora says:

    Hi Liana – this particular experiment doesn’t have a video, since it’s a pretty simple experiment. Occasionally (as in only 2% of the experiments), you’ll find text instead of text and a video. Most experiments have videos… so if there’s another that you can’t access, let me know so I can help.

  10. Liana Oyola says:

    Hi, I am unable to access the videos. It seems videos have been remove. Let me know how can they be access. Tks!

  11. Lisa Banister says:

    i love it so cool to see the change and the amount of drops can change the out come

  12. Aurora says:

    Welcome to our science family! I wonder if you dried off the penny completely between each trial? 🙂 You’ll get the same results if you do the same experiment exactly the same way each time (which is really possible with this one, or most science experiments by the way). What most scientists would do is take an average of the trials for their final result. 🙂

  13. Opal and Flora Radding says:

    Hi Miss Aurora,
    I am a new student of your class. I am excited!
    I did the penny experiment 12 times!The first time I did a shiny penny from 2013 on tails.I did 3 tests on everything.I got 26 26 24. Then I did the same penny on heads. I got 27 25 25.After that I decided to do 6 more tests. 3 on same penny on heads from a close distance and 3 on same penny on heads far distance.on close distance i got 21 21 15 and on far distance i got 11 11 8. Every time except expirements 4 5 6 i got same number same number smaller number! Is that just a coincedence or is there some reason that it happened that way? Thank you!!!
    Opal, age 10, 4th grade

  14. says:

    I got 19 on one try.

  15. Patricia Petraro says:

    My name is Hope and I am Patricia’s daughter. I tried this experiment and I love it! I came up with the idea to do two different experiments using 8 clean pennies and 8 dirty pennies. My hypothesis was that the average amount of drops for 8 dirty pennies would be 24 and the average amount of drops for 8 clean pennies would be 36. It turned out that the average amount of drops for 8 dirty pennies was 21 and the average amount of drops for 8 clean pennies was 31. Thanks for the experiment, Aurora! 🙂

  16. Aurora says:

    Wow – that’s fantastic work! 🙂 And you know, I have no idea what the name of the shape is because the shape changes with the amount of water on the penny, correct? A perfect ball of water is a sphere, but when you add more, you’d have to fit the curve/shape to a math equation that best describes it, which could be parabolic, hyperbolic, logarithmic, polynomial, or something else. Nice work and great question.

  17. Lizet Constanza Mueller says:

    What is the mathematical name of the dome shape that the water forms on the surface of the dome?

    Our children observed that the amount of water the penny holds depends on the distance from which you drop.

  18. Aurora says:

    Those are great experiments! Yes you are absolutely right: oil has a higher viscosity and surface tension than water. The reason for this is that the oil molecules have a stronger bond than the water molecules because oil molecules are very large. These large molecules use stronger bonding forces to stay together. Have fun!

  19. Victoria VanTassel says:

    We just did this experiment, and used both, water and vegetable oil. We got 10 drops (big dropper hole 🙂 ) of water, and 14 drops of oil in several attempts consistently. Now, we need to know why that is that the oil stayed on the penny better? Higher surface tension? Or because of the higher viscosity? My spouse and I can’t agree on whether or not viscosity and surface tension have any correlation. Help us please, our kiddo demands an answer from us, and we are really not sure what to tell her. 🙂

  20. Pamela Church says:

    i tried a quarter and a penny but the quarter did not work any better than the penny. why?

  21. Leslie Nutt says:

    Hi I am lilly i am 11 i did it it was cool my gess was 10 to 15 i got 20 the 1st time and 41 the second. we did a quarter and we got 30 the penny was smaller but it worked better … thank you so much lilly

  22. Beth Beguerie says:

    Thanks Aurora!! I am doing this project for my science fair and I love this experiment! I first Hypothesized 9 drops, and got 22. I love Supercharged Science!!!!! It is so much fun and so helpful. 🙂

    Amanda Beguerie

  23. noahsark says:

    My son who is 8yrs and I just finshied this experiment he really liked the project and is wanting to do more thanks so much!

  24. Aurora says:

    The biggest factor is the size of the drops, which will vary depending on the surface tension of the water (which depends on the minerals and other goodies in the water). When I did this experiment, I picked a coin from my pocket, and it wasn’t especially shiny or new. Make sure if you wash your penny that you get ALL the soap off before doing this experiment, as soap breaks down the surface tension layer and will make the number of drops it holds significantly less.

  25. Hamish McGillivray says:

    This was a really enjoyable experiment and led to interesting evaluations, thank you.
    We repeated the experiment three time (for each side of the coin) – we even had an penny from USA! not bad for an Aussie – and averaged 28 drops for the tails and 29.3 for heads. But as we repeated the experiment, each time the coin took fewer drops.
    We thought that perhaps our constant variable wasn’t all that constant – perhaps each time we cleaned up the water we cleaned the coin as well. Do you know whether the coin that held 70 drops was clean or well used and grimy? Or perhaps it is some other variable we didn’t recognize.

  26. Celeste Mcveigh McVeigh says:

    Loved this! My 6 yo and 8 yo thought this was so much fun! We’ve been dropping water on coins for 30 minutes now! Trying wet then dry! Really fun! 🙂

  27. Aurora says:

    Hmmm… good question. Why do you think that is?

  28. Richard Gress says:

    I did this experiment with both a wet coin and a perfectly dry one, and overall the wet one held more then the dry. Do you know why that would be??

  29. Danielle Elizalde says:

    i did this with a quarter and it held 31 drops!!

  30. Danielle Elizalde says:

    my hypothesis was 10 drops but it held 24!!!!!!!!!

  31. Carmenza Coleman Salgado says:

    I hypothesized 4 drops, but I ended up having an average of 23. This is so cool!!! Great experiment, Aurora!!

  32. Michelle Trimmer says:

    Very cool experiment! We hypothesized 6 drops, but ended up with an average of 13. Our dropper had a rather large opening. We would like to test it out with a different dropper and different coins. My 6 yo and 9 yo both enjoyed this experiement. I love that there is virtually no prep time involved!

Have a question?

Tell us what you're thinking...

You must be logged in to post a comment.