So my friends are gone now. The best part of the weekend had to be when I woke up randomly from where I was sleeping on the inflatable mattress with Joanna and I looked over and saw Justin asleep in my bed with my stuffed loaf of bread in his arms. It's just so... squishy and lovable!


In other news, how do Enrique Iglesias be so fine?????

You call me on the phone
I act like nothing's going on
We're driving in my car
I pretend that you don't turn me on

In other other news, everyone seemed to like my presentation on the nucleation of bubbles in magma chambers leading up to explosive eruptions. You see, when you boil water, there are three ways that it can start turning into a gas. First, it can just start evaporating off the top, coming up as steam. This only happens at the interface between the water and the steam.

Second, bubbles can form homogeneously throughout the water. This is difficult because not only must the water gain enough energy to turn to steam, it must also gain enough energy and pressure so that the bubble can push and hold back the water once it is formed (it has to overcome the viscosity of the water in order to push it). Thus water has to be at way more than 100 C in order for this to be able to happen. They call that "overheated" or "superheated".

The third way is that bubbles can be nucleated inside tiny cavities in the container (or in anything floating in the liquid) that are due to imperfections in the surface. This is because the pressure and temperature inside the cavity may not be the same as in the liquid in general, allowing a bubble to form without as much energy required. Eventually it grows enough in this environment and fills up with enough gas that it can escape the cavity into the liquid. As it rises, the pressure decreases and the bubble grows, finally reaching the surface and popping. So you'll increase the size and number of the bubbles if you decrease the pressure confining them (see: popping the cork on a champagne bottle).

Once you have a lot of bubbles, the way to make the mixture explosive is to let all the bubbles coalesce, so that instead of having some bubbles floating in a liquid, you suddenly have liquid suspended in a gas. Sometimes you'll get really strong bubbles and they'll be touching but they won't coalesce. You can speed along the process if you want by reducing the surface tension on the bubbles. Organics are very good at doing this in water. For example, have you noticed that when you're cooking pasta, at one point the pasta, which was nicely boiling just a minute ago, suddenly goes crazy and boils like nuts gets frothy and spills all over the stove? That happens because the organic molecules in the pasta have been leaching from the pasta and they reduce both the surface tension of the bubbles, as well as the surface tension at the surface of the water, allowing all of the bubbles to break through it and froth over. An ingredient with a similar effect is present strongly in Mentos, which means that if you drop one into a beverage with a lot of bubbles waiting to be exsolved, it will cause them to exsolve and coalesce... and become explosive. See: YouTube videos.

When they make champagne flutes, they blow the glass for the flute and then they pull it off at the base of the bowl. This means that most of the imperfections will be in the center of the bowl at the bottom. So when you pour champagne in the class, the bubbles nucleate there at the bottom and tend to spiral upwards to the top. They actually care to construct these flutes in this way so that you'll get a classy bubble pattern when you pour your champagne.

So what am I saying? If you have a flawless pot then it will take a lot longer for your water to boil? If something takes a long time to boil, it's going to be much hotter when it finally does? If you're very flawed and under pressure you're more likely to explode?

Nah.

I think I'm saying that it's not your fault that every time you make spaghetti your pot boils over.

And also that sometimes having a few flaws here and there can make for a gorgeous glass of champagne.

I didn't know that about bubbles. I think it would be cool to watch someone make a champagne flute or anything out of glass.
» Southern on 2007-05-29 03:05:40

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