When you are making an agarose gel at one point the mixture of agarose and water might be heated in a microwave. Why would you also put in a glass of water in the microwave? I think some how the glass of water some how prevents the agarose mixture from boiling over. But how does this really work?

 

This may be a chemistry physics question.

Not everyone is doing that. At least I do not know anyone who does it. What I could imagine is that it is an attempt slow down the heating, but then you may get the same result by using a lower setting (though some may not allow that).

Never heard of that one. We just set the microwave to medium.

Don't screw down the lid of the Schott bottle... had a tech do that in a lab I used to work in. The results are spectacular, but undesirable.

While we are at it, do not put the hot bottle near your eyes to check whether everything has been dissolved. Superheating is no fun, tight cap or not.