Fill a glass up to the top with water.
Carefully add more water.
You can slowly add more water until the water level is higher than the top of the glass! The reason is because the tiny water molecules are "holding on" to each other. This is called "surface tension."

Cut out a small piece of cardboard, roughly in the shape of a boat.
Drop your boat into a bowl of water. When the ripples settle down, notice that the boat doesn't go anywhere.
Turn the boat over and put a small drop of soap onto the back of the boat. Drop the boat onto the water again, just like before. Watch it zip across the water! When you first dropped the boat onto the water, the surface tension of the water molecules was putting an equal force all around your boat. Soap breaks the surface tension at the back of the boat, so the unequal surface tension at the front of the boat pulls the boat forward. You'll need fresh water to try this experiment again.

Put some water in a bowl, then pour some vegetable oil into the bowl. The oil floats on top of the water.
Let a drop of soap fall into the middle of the bowl. The oil instantly flees to the sides of the bowl!
Try swirling the water with your fingers to break the oil into small "bubbles." Then push the small bubbles together to make bigger bubbles.
Try coating the water with pepper, then sprinkle or pour various things such as salt, sugar, ketchup, vinegar, syrup, food coloring, etc., and watch through the side of the bowl to see how those things interact with the "soup" you're making! Don't drink this "soup"!

When it's time to clean out the ice-maker in your freezer, dump the ice into a sink or bathtub. Use a pitcher of water, or a spray hose if your sink has one, or simply use the faucet and have fun sculpting and destroying the ice with warm water!

This is a fun little puzzle that you can easily make. Cut out 9 small squares of paper and write the numbers 1 through 9 on them, or use the Ace through 9 from a deck of cards, and line them up in a row from 1 to 9. (For taking a picture, it worked out better to group them into 3 rows, but you'll probably prefer to have the numbers all on one row.) Roll two dice. The picture shows a 3 and a 6. The idea is to remove some numbers which add up exactly to your dice roll. In this case, we could remove the 9, or the 6 and 3, or the 5 and 3 and 1, etc.
In this example we "sliced away" the 6 and 3, then we rolled a 2 and a 4. Now we can slice away either the 4 and 2 or the 5 and 1. Notice that we can't slice away the 6 because it has already been removed.
Continue "slicing and dicing." If you are able to remove all of the numbers then you win! However, you will usually end up with a dice roll which won't allow you to remove any more numbers, as in the picture. When that happens, you'll probably want to try the puzzle one more time. It's hard to quit!