Why sublimation occur?

When solid absorbs enough heat to change from solid to liquid then to gas. But some substance like dry ice can change from solid directly to gase. This is because of the nature of that substance when subject to atmospheric pressure, sublimation can happen. When dry ice is placed under ocean having higher pressure, it can change to liquid then to gas. So at atmospheric pressure, dry ice will sublimate any any temperature above the mp of dry ice, there will be no bp.

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