Test Tube Science: 1+1≠2

Materials:
   -Two test tubes
   -5 mL rubbing alcohol
   -5 mL water
   -One pipette  
Background:
Dissolving sugar in water is a common enough sight.  Dissolving two liquids in each other is less commonly noticed.

Directions:
Put 5 mL of rubbing alcohol in one test tube and put 5 mL of water in the second test tube.  Now use the pipette to transfer the rubbing alcohol to the water test tube.

Now look at the volume of the mixed test tube.  If the two liquids mixed but didn’t dissolve there would be 10 mL of liquid in the new test tube.  How many do you see?  Can you find any other liquids that will dissolve in each other?