Prior to the experiment, freeze red colored water into a heart shape using a candy mold or similar. (A regular ice cube will work too!)
Fill a tall, glass cylinder about 1/4 full with water. Fill about another 2/3 full with vegetable oil.
Gently add the ice cube. Will it sink or float? It should sink a little, but not all the way. Why is this? Now watch as the cube slowly melts. The melted drops quickly sink all the way to the bottom. Why is this? For comparison, repeat this in a regular glass of water. What are the similarities and differences?
Extension: Try adding a layer of baby oil to the top. The baby oil should float on top of the vegetable oil. When you add the ice cube, the cube will sink down through the baby oil but not the vegetable oil! Note that we had trouble doing this with a generic store brand of baby oil; it works well with Johnson's Baby Oil.