What is dry ice ? what happens when the pressure under which it is stored is decreased to 1 atmosphere? ?

Dry ice is solid carbon dioxide  

Explanation:

It is not stored under pressure.

At 1 atm, it sublimates (changes directly from a solid to a gas) at  -78.5 °C.

Dry ice is nothing more than the solid form of .

Explanation:

It starts sublimating (goes from solid form directly to gas form) at -78.5º C, at a standard atmospheric pressure (1 atm), meaning can be preserved in its solid form at temperatures lower than -78.5º C.

Hope it helped,

BiologiaMagister