Homeschool Science Experiments: Surface Tension

Recently in his science textbook, Big Brother had read about a pond insect called the water strider that is actually able to glide across the surface film of the water in the pond. To illustrate how this is possible, we conducted a simple experiment!

What we needed:

1. A bowl of water
2. A pair of tweezers
3. A sewing needle

Big Brother filled the bowl with water and set it on the kitchen counter. I told him to carefully pick up the needle using the tweezers and very gently set it on the very top of the water.

What would happen? He was totally surprised when, rather the sinking to the bottom of the bowl, the needle actually sat on the surface film of the water! Just like the water strider we had read about!!

Now I asked him to give the needle a gentle nudge with the tweezers. Now the surface film was broken and the needle did sink.

This little experiment was so simple, but Big Brother really thought it was cool! I gave him some time to repeatedly set the needle on the water's surface and watch it just sit there before he would push it on down to sink into the bowl.

Along this same water theme, we conducted another simple experiment involving surface tension.

What we needed:

1. A glass filled to the brim with as much water as possible
2. A roll of pennies (or you could use paper clips or similar small objects)

This time I carefully filled a glass to the tip top with water. I gave Big Brother the pennies and told him to drop in one at a time very gently. Each time he dropped in a penny, we watched the bulge that formed at the top of the glass as surface tension kept the water from spilling out of the glass.

Then we made a game of it! Just how many pennies could the glass hold before the surface tension could no longer hold in all the water??

We were both quite surprised to find that it took 15 pennies before a trickle of water finally came spilling down the side of the glass!!

We love doing experiments and making real life observations that relate to what he is learning from his textbooks!!

I want to challenge your family to give these experiments a try and post your results in the comments! Were you able to see the needle float? How many pennies or other coins/objects did your glass hold before some water spilled out?