Â­. Â­Dry ice is frozen carbon dioxide. A block of dry ice has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C). Dry ice also has the very nice feature of sublimation -- as it breaks down, it turns directly into carbon dioxide gas rather than a liquid.
The time for a broken collarbone to fully heal depends on the severity of the injury. In children, complete healing may take as little as three to six weeks. In adults, six to 16 weeks or more are often necessary for a collarbone to heal solidly.
1 Treatment for a broken collarbone usually requires a sling or figure-of-eight splint to keep the area immobile for several weeks. In some cases, surgery may be required.  Most clavicle fractures heal within 4 to 8 weeks. Physical therapy may help with rehabilitation.