How does ice sublime, and what are the key conditions required for this process?

**Answer:** 1. **Sublimation Definition**: Sublimation is when a solid turns directly into gas without becoming liquid first (e.g., ice → water vapor). 2. **Why Ice Sublimes**: At low pressures (below **0.006 atm**) and temperatures below 0°C, ice molecules gain enough energy to escape as vapor without melting. 3. **Example**: Dry ice (solid CO₂) sublimes at room temp, but normal ice does it slowly in freezers (frost buildup). **Key Condition**: Low pressure or very dry air speeds up sublimation. Want a deeper breakdown or real-life example?