This is a simple project, which kids might get some fun out of. It just involves a straw in a mason jar, with about an inch of water. You blow into the straw and a water fountain appears.

Supplies

Mason Jar
Straw
Water

Tools:
Nail and hammer or drill to make hole in lid.
Hot glue gun

Step 1: Make a Hole in the Lid

I made a hole in the lid for the straw to fit in with a nail and hammer. A drill will also work.

Step 2: Glue in the Straw

With the hot glue gun, glue the straw into the lid. Glue both sides of the lid and glue it in well.
The bottom end of the straw should almost reach down to the bottom of the jar.
Wait for the glue to set.

Step 3: Add Water, and Blow Into the Straw.

Add about an inch or so of water into the jar so the straw is in the water but at least 3/4 of the jar is air.

Screw on the lid.

Blow into the straw and when you take your mouth away, a small water fountain will appear.