STEM Third-Fourth Grade Experiments

Dow would like to thank the Chemical Educational Foundation® (CEF) for permission to use these materials. Dow is a Diamond sponsor of all CEF’s You Be The Chemist® programs. For more fun ways to incorporate science into everyday life, head to the Chemical Education Foundation’s Activity Guide.

Learn more about science by exploring these experiments:

TOY BOAT EXPERIMENT

  1. Fill a sink or any container with fresh, clean water.
  2. Now, cut out some cardboard or heavy paper in the shape of a boat.
  3. Make your boat small, about the size of a postage stamp.
  4. Once your boat is cut out, make a small notch in the back.
  5. Put a small dab of soap in the notch.
  6. Set your boat in the water and watch it speed around!

Scientific Principle at Work
Surface tension represents the way liquids, like water and vegetable oil, act when they are mixed together. Surface tension is measured by scientists in a unit called “dynes” per centimeter. Tension is created by the attraction of molecules toward the interior.

Soap has molecules that are designed by chemists to dissolve in water. The action of dissolving reduces surface tension mixing soap molecules among the water molecules on the surface of the water. As the soap dissolves in the water, it creates a force that moves the boat forward.

COMPETING WATER DROPS EXPERIMENT

Find two identical drinking straws.

Fill two glasses with some fresh water. Mix a squirt of dish soap into one of the glasses.

  1. Using both hands, lower the two straws into the two glasses at the same time.
  2. Next, covering the top openings with your thumbs, lift the two straws out of the glass and watch what happens.
  3. You will notice that the straw that was placed in the soapy water has smaller droplets of water that drip off of it while the straw in the plain water makes larger drops.

Scientific Principle at Work
Dynamic surface tension measures the attraction or “strength” between molecules in the liquid. The surface tension governs how much weight a drop of water can hold before it is too heavy and falls off the straw. Reducing the surface tension by adding soap means only smaller drops of water can form before falling off.

THE INCREDIBLE SHRINKING MILK JUG EXPERIMENT

Find a one-gallon, plastic milk jug. Go to the sink and run some hot water.*

Put a half-inch or so of hot water in the jug and then put on the cap. Now shake the jug so the water spreads around the inside of the jug. You should see the jug expand or get bigger.

Now, take the cap off and pour out the hot water. Next, run the same amount of cold water in the jug. Cap it again and shake. Watch the jug shrink!

Scientific Principle at Work
Gases like air expand or contract with temperature. When the molecules (they’re the building blocks for everything) are heated, they move faster. When molecules are cooled, they move slower. A law in chemistry says for a given volume and number of molecules of vapor, the pressure follows the absolute temperature. You saw this law when the jug expanded and then shrunk.

*Note to teachers and parents: Be sure to supervise this experiment with younger children.

Additional Experiments:

Goofy Putty Experiment

Milk Rainbow Experiment

Note: If you’re under the age of 18, be sure your parent or guardian knows what you are doing. Some of these experiments require the use of simple household tools, such as scissors and knives, and some could make a mess. Ask your parent or another adult to help.