Carbon dioxide at room temperature and air pressure is a colorless gas; it doesn't look like anything. Liquid carbon dioxide looks like water. Solid carbon dioxide (dry ice) looks like smoking ice. If you leave a piece of dry ice out on a table top, it will sublimate, that is, it will change from a solid state to a gaseous state without going through a liquid state. Both liquid and solid carbon dioxide are produce by application of pressure and the draining off of the resulting heat of compression.