Frozen broccoli thermodynamics

[Frabjous]

I was cooking frozen broccoli in a microwave with a couple of tablespoons of water in a plastic bowl. I left the cover loose to prevent steam pressurization. When I opened the microwave, the cover had been sucked into the bowl due to differential air pressure.

What is the mechanism?

 

[A.T.]

I was cooking frozen broccoli in a microwave with a couple of tablespoons of water in a plastic bowl. I left the cover loose to prevent steam pressurization. When I opened the microwave, the cover had been sucked into the bowl due to differential air pressure.

What is the mechanism?

First it heated up (air out), then it cooled down (tried to suck air back in).

 

[jbriggs444]

What is the mechanism?

I would speculate that the water in the plastic bowl was intermittently boiling due to rotation of the bowl in to and out of the "hot spot" in the microwave. Meanwhile, the ambient temperature within the microwave was below the boiling point. This led to the steam in the bowl condensing and sucking the top on.

This is similar to home canning except for the time scale.

 

[SammyS]

I was cooking frozen broccoli in a microwave with a couple of tablespoons of water in a plastic bowl. I left the cover loose to prevent steam pressurization. When I opened the microwave, the cover had been sucked into the bowl due to differential air pressure.

What is the mechanism?

I suspect that enough water evaporated quickly enough so that a significant fraction of the atmosphere in the bowl was water vapor. Upon cooling much of the water vapor condensed - perhaps relatively quickly.

(jbriggs44 beat me to it. )

How well was the broccoli cooked?

 

[Frabjous]

How well was the broccoli cooked?

About right. It was in for six minutes.

 

[gmax137]

Sometimes I stretch plastic wrap over the dish/bowl to prevent spatter. Even if I open the door immediately when the timer ends, the wrap will be sucked down onto the contents. It doesn't take long!

 

[Tom.G]

Sometimes I stretch plastic wrap over the dish/bowl to prevent spatter.

Often a deprecated approach.

The plastic has been known to melt and/or even catch fire.

Many people dislike the tast and/or smell of the outgassing of volatiles from the plastic -- and don't care to ingest those volatiles as they drip back down to the food.

Safer to put a plate over the bowl.

Stay safe,
Tom

 

[gmax137]

Many people dislike the tast and/or smell of the outgassing of volatiles from the plastic

It can't hurt broccoli. Just kidding.