First, a bit of backstory. At every family meal, Lucien plays a make-believe game. The dining table is an airplane, the kitchen is the galley, Daddy is the pilot, Mama is the flight attendant, and he is the passenger. The flight attendant helps to buckle him in his airplane seat and brings him his food tray and ice water; the pilot checks the flaps and ailerons, taxis down the runway, announces our altitude, and turns on autopilot. Then the pilot illuminates the fasten seatbelt sign. Our fasten seatbelt sign is, in reality, a candle. So we always have a candle lit for meals.
One evening, toward the end of dinner, Lucien was getting fidgety and curious, and he blew out the fasten seatbelt sign, then dropped it into his water.
The pilot remarked that Lucien had devised an interesting science experiment. What happens when you drop melted wax into cold water? For the next half hour we sat at the dinner table and found out.
Lucien explained to us that he wanted to stir up the wax and mix it into his water. He tried, without success. The wax did not dissolve.
Daddy explained that wax is a lipid, or a fat, and that fats are hydrophobic, and therefore do not dissolve in water. He also explained to Lucien why he has to wash his hands with soap after he eats “fatty pieces” (his favorite part of a steak) … because those lipids are hydrophobic as well and do not rinse away with just water.
I told him that hydro means water, like hydrate – a word he already knows – or hydroponic, a word he has heard. And that phobic means afraid. Because, you know, I explain Greek roots to my toddler.
Then we went on to drop hot wax into the cold water and observe the results. When we dropped small drops into the water they hardened immediately, forming circular patterns. When we dropped large globs of melted wax, the portion that came into contact with the water hardened more quickly. This produced some interesting results. Lucien succeeded in making a hollow wax “boat” and then dumping out the extra liquid wax. He also made a couple of “icicles.” We talked about the states of matter – how wax can be a liquid when hot and a solid when cool, and how water can exist as a solid or liquid (this is where further discussion of icicle formation came in) or even as a gas.
We went through two candles that day – you will notice white and purple wax in Lucien’s bowl – and I left all of his science supplies out on the table for further exploration. He returned to them the next morning, when we had some more fun sensory and imaginative play; he made and sailed a sailboat.