This leakproof bag science experiment is fun and easy to do with your kiddo. My son saw this and was describing it to me, so I Googled and found a how-to from the Indianapolis Public Library. We tried the experiment and we were so excited that it really worked! Wow, we couldn’t believe that we could actually poke pencils through the bag without the water coming out! We were so impressed!
Supplies Needed:
- Ziploc bag (we used gallon sized)
- sharp pencils
- food coloring (optional)
- large bowl (optional)
How To:
We filled our bag halfway full with water and a added a drop of blue food coloring to dye the water. While this is totally optional, it did make the project more colorful and more fun for my blue-obsessed kiddo.
Next, we moved our project to the table and I held up the bag over a bowl (I was worried there would be a leak). I’m glad I had a bowl, because during the experiment, our bag did begin to leak (more on this later). While I held the bag, my son shoved a sharpened pencil through one side of the bag, through the water, and out the other side. Wow, it didn’t leak! We were all really impressed. My kiddo continued to stick in the pencils until he ran out of pencils.
TIP— when sticking in the pencils, try to keep the pencils far apart from each other. My son stuck one pencil right next to another pencil and that did make a small hole. Water started slowly leaking from the hole in the bag. Good thing we had bowl underneath.
The small hole my son accidentally made lead to a learning experience — the Ziplock bag clings to the pencil, forming a seal that keeps the water locking. However, when two pencils touch, the bag isn’t able to make a seal in between the pencils so we got a leak.
After you have stuck all of your pencils through the bag, hold your bag over the sink and slowly remove the pencils. Water will come out of the holes. We dried our pencils with a paper towel. They were totally fine and ready to color with the next day.
So why doesn’t it leak? Our friends at the Indianapolis Public Library say plastics are bendy and stretchy because of their flexible molecule chains, so when you stick your pencil through the plastic bag, the plastic makes a seal around the pencil.
Check out more preschool STEM ideas: https://imaginationsrunningwild.com/stem/