Water's Tensile Strength--Water Science

 Today we did an experiment...an oldie but a goodie...What makes it even more fun is the fact that this bunch of kids have never done these particular water experiments before.  I forget sometimes that even if something has been done in our homeschool before there are several children who may not have experienced it before.

This time we took a guess has to how many water drops we could get to stay on the top of a penny, (or nickel or quarter)  The guesses ranged from 8 to 10, which, with 4 kids making hypothesis surprised me.  I think they were influenced by each others guesses.

 

 If fact, the highest number of drops was 19.  We learned about tensile strength and the fact that water definitely has "strength" on the outside "skin" of the water.

 Once the water started to flow, it all flowed off the penny.

 31 drops were put onto a nickel.  (This surprised me!)

 We then tried a new to us experiment.

We filled a jar to the very top.  Next, drop pennies gently into the jar, trying not to disturb the water.

 Mark managed to drop 36 pennies into the jar.  In the process a beautiful dome of water rose above the rim of the jar.  The 37th penny sent the water flowing from the jar.

 And what does dish detergent do to the surface of the water.

Sprinkle a bowl of water liberally with pepper.

Dip a toothpick covered with dish detergent into the center of the pepper.

Watch the "magic" happen....or is it science??

Water-The Unplugged Project of the Week

"Water, water everywhere, nor any drop to drink." Rime of the Ancient Mariner

This line kept going through my head all the past week as I was thinking about the Unplugged theme of the week-WATER. I wasn't up to diving into this epic poem, so I settled on some fun water experiments.

Our first experiment is a magic toothpick trick, which showed us how dish detergent breaks the surface tension of water.

We needed:

six toothpicks

dish detergent

a pie plate of water

At first we arranged 5 toothpicks into a pentagon in the pie plate of water.

It took some patience to form this pentagon, but we did it.
We then dipped the 6th toothpick into dish detergent.
When we poked this toothpick into the water at the center of our pentagon,
the pentagon toothpicks immediately floated away from each other. We learned that the soap broke the surface tension of the water, making the molecules of water break apart from each other. We see this when the toothpicks spread out.

Another fun surface tension experiment is seeing how many drops of water you can get on the top of a penny with a dropper.

First, we took guesses as to how many drops the pennies would hold. The kids guessed one or two.

It was very exciting and impressive when we managed to put 24 drops of water on the top of a penny. We carefully checked out our dropper and 20 drops is about 1 ml. We could see the surface tension of the water holding actually over the edge of the pennies.

We learned that water molecules are so attracted to each other the want to stay "stuck" together. If we poked the water with the tip of a toothpick, the tension was broken and the water flowed off the penny.

VERY COOL!

Becky set the record with 29 drops of water on a penny.

We then set out to find out why they put salt on our roads in the winter.

Using a:

bowl of water
string

table salt

ice cubes,

we discovered how to lift an ice cube with a string.

We put the ice into the water, laid the string on top of the ice, and then shook salt onto the string and ice.

After waiting about a minute, TA DA, the string picked up the ice.

The salt lowers the freezing point of water. The ice melts around the string and then refreezes with the string frozen to the ice.

Gracie did it,

and so did Luke.

Make sure you go and check out all of this weeks Unplugged: Water activities.