Condensation is the changing of water vapor in the air into water. This can happen when warm, moisture-laden air touches a cool surface. Demonstrate condensation by taking a picture of a mirror in a bathroom. Then have someone take a hot shower. When they are finished, take another picture of the mirror and compare the two pictures.
Another way to see condensation is to fill a kitchen pot with water and place a lid on it. Have an adult put the pot on a stove and boil the water for several minutes. Have the adult remove the pot from the stove. Let it cool. When the pot is cool and safe to touch, remove the lid and look at its underside. You will see water droplets clinging to the lid.
Show the child how magnetism works underwater. Tie a string to a magnet. Make a pile of small paper clips. Lower the magnet into the pile and gently pull up, collecting as many paper clips as you can at one time. Remove the clips and count them. Make a pile of paper clips in a deep plastic or ceramic bowl. Fill the bowl with water. Lower the magnet into the water and onto the paper clip pile. Slowly pull the magnet out of the water. Count the number of paper clips you collected. If the number is very close to the number of paper clips captured in air, you might come to the conclusion that water has little or no effect on magnetism.
Experiment with bubbles and formulas. Use the formula of one measure of water to one measure of dish detergent and one-half measure of glycerin to make a bubble mixture. Make a second batch, using sugar in place of glycerin. Finally, make a third batch, substituting corn starch for the glycerin. Test each mixture to see how big you can make bubbles, how strong they are, and how long they seem to last without bursting. Decide which formula works best.
We can see the source of light and we can see objects that light shines on, but we don't see the actual beam of light when it travels through the air. To see a beam of light we have to put something in its path so the light can bounce off. In a dark room, set a flashlight on a table. Position it near the edge of the table, with the light facing out into the room. Place a book on each side of the flashlight to keep it from rolling. Turn the light on. You will see the light of the flashlight and you will see light on the wall. To see the beam itself as it travels through the air, shake a facial tissue above the light. Tiny particles of tissue paper will float in the air, and the light will bounce off of them, showing you the beam of light.