Endothermic Decomposition Experiment

[spicegirl]

I am doing an assignment and I'm not sure if the answer is endothermic decomposition someone please help me!
During an experiment, a metal and an excess of fluorine gas were placed into a combustion chamber at a temperature of 1800°C. The temperature in the sealed chamber continued to rise to 2100°C. After the reaction stopped, a brittle white substance, which dissolved in water, was extracted from the chamber. From this evidence one could conclude that this reaction can be classified as

 

[berkeman]

I'm no chem expert (by any means), but if the sealed chamber's temperature rose during the reaction, would the RX be endothermic? What are the other options...?

 

[t!m]

And if two things went in and one thing came out ... would the rxn be a decomposition?

 

[Gokul43201]

I am doing an assignment and I'm not sure if the answer is endothermic decomposition someone please help me!

This is not an attempt at a solution. This is just a wild guess.

At the very least you should tell us what you think is decomposing into what.