what is this substance called?

Question

my mom says she remembers a susbstance from her chemistry classes a long time ago.she forgets what it is called, but i will explain it. she said it was a semi solid substance that her chemistry teacher had in a jar a long time ago. the teacher would take prongs and take a little of the substance out of the jar and quickly put the lid back on. she said it was a grayish color and it would spontaniously combust when it touched air. what is this substance called?

Answer 1

Potassium probably, maybe sodium

Answer 2

If her teacher took it out quickly and put the lib back on, air cannot have caused spontaneous combustion unless the substance in the jar (also exposed to air in the opening) combusted as well. My guess is what your mother remembers is potassium, which is grayish, and reacts violently with water (a common demonstration). If she is certain that the substance reacted in the air but the rest in the jar did not, it is possible that the substance was something more rare and more highly reactive, such as certain forms of lithium or francium both also greyish. However, these substances are highly dangerous and certainly would not be safe to have in a jar that one intended to ever open in the presence of air unless they were highly diluted in something else. Of course, there are many millions of rare (usually expensive), dangerous, complex molecules that I have never heard of, so it is possible that the substance was something different entirely. My bet's on pure potassium.

Answer 3

Magnesium

Answer 4

Sounds like it could possibly be potassium or lithium

Answer 5

I think it may have been : sodium , potassium , lithium or calcium

Answer 6

Maybe white phosporous (was it kept under water?)

It could also have been potassium, rubidium, or cesium (it would have been kept under oil or kreosene)

Answer 7

dry ice

Answer 8

it could be sodium...