We are studing physical changes, and chemical changes at
school. my daddy told me to ask the teacher if a solid can go right to a
gas witout being a liquid first.she said that carbon dioxide can, but not
ice. Dad says she is wrong. would you help me with this one. thanks.
Your daddy is correct. Whenever a solid goes directly to the gaseous condition
-- without first melting -- the process is called sublimation. As you already
know, dry ice can do this. So can solid iodine, naphthalene (moth balls),
paradichlorobenzene (moth crystals), camphor, menthol, and other compounds as
Ordinarily, ice melts before it becomes a gas. Nevertheless, ice can
"evaporate"-- sublime -- just as your father says. Though it does not
that often, when the humidity is low and the temperature is just below
freezing, even snow (which is ice) can also sublime. Ice will sublime if
placed in a vacuum, even if the temperature is well below freezing. Your
a smart fellow.
Click here to return to the Chemistry Archives
Update: June 2012