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00:00But why does water get wet?
00:02Water gets wet thanks to the electrostatic interactions
00:05between water molecules and the materials it touches.
00:08When a drop of water comes into contact with a surface,
00:11it forms a contact angle.
00:13The smaller this angle is, the more the drop spreads,
00:16thus increasing the wetness of the material.
00:19For example, on glass or a cotton ball,
00:22water spreads well by forming a weak contact angle.
00:25This capacity for water to spread and get wet
00:28is due to the intermolecular force
00:30that binds the water molecules to each other and to the material.
00:33However, on certain surfaces,
00:35such as teflon or yellow wax,
00:37on beaches,
00:39the contact angle is very important,
00:41which prevents water from getting wet.