Got Science?

Got science, anyone? Sorry, I couldn't resist. Hope everyone is enjoying their spring break despite the rain!

So, to the question box. My source for this is not a link, a book, but an engineer!! So, I have no link for you. The question was: How does jello solidify? The answer lies in the concepts behind heat transfer.

We all agree that jello needs to be cooled down in order to solidify, correct? So, really, jello solidifies according to how heat is lost- where the jello loses heat, it solidifies. However, the heat needs to be transferred to something else in order to "lose" heat- by conservation of energy, as we learned in class. Thus comes in handy dandy convection. Convection is heat transfer using a fluid- i.e., a liquid or gas. The fluid that is doing all the transferring in the jello scenario is not the jello itself, but the air around the jello. If we put jello in a pan, it has contact with the air. As the heat from the jello warms up the air around it, the air rises and starts moving, allowing cooler air to take its place. This type of convection, caused solely by the differences in temperature, is called free convection. But let's say I wanted to serve the jello, or in my case, the almond jelly/tofu-ish thingamajig for desert, and it was already five o'clock. Oh no! How would I speed up this process? Well, it might not be good enough to get it ready in time for desert, but it would speed up the time it took if I placed a fan that blew cold air next to the jello- forcing the air to move faster, taking more heat with it. This is called- you guess it, forced convection. So, the answer to the question? The jello solidifies all around. Wherever the jello (or it's pan) has contact to the air, it will solidify there first, so the last to solidify would be the middle. Now, here's a challenge: apply these concepts to the next question box, coming up soon.

By the way, Bubbly happens to have some good links if you really want them!