While the adsorption of water vapor does not harm silica aerogels, contact with liquid water has disastrous results. The strong attractive forces that the hydroxyl surface exerts on water vapor also attracts liquid water. However, when liquid water enters a nanometer-scale pore, the surface tension of water exerts capillary forces strong enough to fracture the solid silica backbone. The net effect is a complete collapse of the aerogel monolith. The material changes from a transparent solid with a definite shape to a fine white powder. The powder has the same mass and total surface area as the original aerogel, but has lost its solid integrity. Silica aerogels with fully hydroxylated surfaces are, therefore, classified as "hydrophilic".