Our first experiment was to guess which objects would sink or float and then test our hypotheses! We found that objects that were denser than water would sink, and objects that contained air would float. Some floating objects could be made to sink by increasing their density or by squeezing the air out.
Will a plastic spoon sink or float?
How about a pumice stone?
Or a paper clip? The kids had fun guessing and testing.
Then the children were given cups of water sprinkled with black pepper flakes. The pepper floated on the surface of the water, and when Glenn added a few drops of dish detergent, what do you think happened? The pepper dispersed as the detergent molecules bonded with the water molecules and broke the surface tension. This is called the "Runaway Pepper" experiment.
Pepper flakes float on the surface of the water.
A few drops of dish detergent are added to the water.
The pepper "runs away" like magic!
After this experiment, the kids played at the water table and with Glenn's homemade "wave machines." You can make a wave machine at home, too!
A clean and empty 2-litre plastic bottle
Mineral or Vegetable oil
1. Fill half the bottle with water and a few drops of food colouring. Make sure that the water is still transparent.
2. Fill the remaining half with oil. Overfill the bottle so that there is no air at all in the bottle.
3. Put on the cap and seal the cap with duct tape.
Rock the bottle back and forth to simulate waves.
The moms also found them to be therapeutic!
Next, we observed the surface tension of water by carefully adding pennies to a cup of water. As more pennies were added, the water appeared to form a dome (convex meniscus) before running down the sides of the cup. This is because the surface water molecules have a strong cohesion, acting like a skin.
Glenn adds the pennies to a cup of water.
A dome of water starts to form because of surface tension.
The kids stay back because the slightest bump would disrupt the experiment!
Finally, Glenn showed us one more cool science trick - using dish detergent to propel a boat! Cut a boat shape (similar to a house shape) from a cardboard cereal box, and cut a small square at one end. Put a little dish soap at the cut-out square so that just the soap will touch the water, and then lay the boat on the water surface. It will zoom away! As the detergent molecules spread out to bond with the water molecules, it breaks the surface tension and gives the boat a little push!
Cut a boat shape from cardboard.
Add a drop of detergent.
Place it on the water and watch it zoom!
Look for this experiment and more fun things to try at home on Glenn's website: www.somethingincredible.ca.
Thank you, Glenn, for another exciting momstown Victoria Little Scientists program, and also thank you to Saanich Neighbourhood Place for the wonderful space for our program! Next month we experiment with dry ice!
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