The water vapour present in the air comes in contact with cold surface of the glass, loses its energy and gets converted into droplets of water.

The water vapour present in the air comes in contact with cold surface of the glass, loses its energy and gets converted into droplets of water.
Substance | Melting point(°C) | Boiling point(°C) |
X | -219 | -183 |
Y | 119 | 445 |
Z | -15 | 78 |