Sublimation (physics)

Sublimation is a physical process where a solid substance changes directly into a gas, without first changing to a liquid. Imagine a block of ice: when it is heated, the ice melts to water and then boils to become a gas. Sublimation is when this happens all at once and the solid changes directly into the gas. This happens a lot with substances like dry ice (frozen carbon dioxide), which turns from solid to gas without becoming a liquid first.