Why did one plastic container melt in the microwave but not the other?

[Xyius]

I am trying to come up with an explanation as to why this happened.

My dad put a plastic container in the microwave with food in it. He microwaved it, and it turned out fine. He then took that one out of the microwave and put in another plastic container in. Also with food in it. The weird thing is, this plastic container melted in the microwave! Why did this one melt and he other didnt? Could it be possible that the one that melted had more water in the food and therefore was heated up more by the microwave? What are your thoughts?

 

[WhoWee]

Were the containers similar? Were the heat or timer settings different? Please address the variables.

 

[Xyius]

To my knowledge the containers and heat settings were identical. They may have had different food in them though. I cannot find out at the moment. Ill add more info when I am able to get it.

 

[Born2bwire]

Perhaps the food item in the second case had a very low specific heat and/or was a poor absorber. If it has a low specific heat, then it would not take much energy to bring it up to a high temperature. The high temperature could melt the plastic in immediate contact with the item. Or the item could have been a poor absorber of microwaves. In which case the microwave cavity could have been permeated with a much higher energy density than before. This would allow more energy that could be absorbed by the plastic container which would heat it up to higher temperatures than before.

Or perhaps the container was still preheated from the previous microwaving.