Everyday physics/chemistry

[serenissima]

An interesting phenomenon:

I make tea at the office by heating my mug of water in the microwave for a couple minutes. I usually put half a packet of Splenda in the water first, and there's also tea residue left in, as I only take the mug home to wash it every few days.

The water is no longer boiling by the time I open the microwave door. But if I get there quick enough, dropping the tea bag in results in a sudden, brief flurry of bubbles. Why?

Comments

[ceruleanst.livejournal.com]

Nucleation sites, I think. The water is still hot enough to boil, but there aren't as many places for bubbles to form until the porous tea bag is introduced.

[stryck.livejournal.com]

Exactly! The water is 'superheated', but without any place for bubbles to form, it doesn't actually boil.

[zeeth_kyrah]

Which is why one should be careful of water that's just been microwaved. It's also why I like to add a bit of salt when I'm boiling water for pasta or soup.