Complete the following sentences :
Decrease in pressure over ice .................. its melting point.

Explanation

To complete the sentence, we need to understand the relationship between pressure and the melting point of ice.

1. **Understanding the Concept**: Ice has a unique property where its melting point is affected by pressure. According to the phase diagram of water, when the pressure over ice decreases, the melting point of ice increases.

2. **Applying the Concept**: Based on the relationship between pressure and melting point, we can conclude that if the pressure is decreased, the melting point of ice will increase.

3. **Final Completion**: Therefore, the completed sentence is: "Decrease in pressure over ice increases its melting point."