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When some wax is rubbed on a cloth, it becomes waterproof. Explain. |
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Answer» The cloth is made of fine fibers and the spaces between the fine fibers act as capillary tubes. We know that when the angle of contact between the water and the side of the capillary tube is less than 90°, the water level in the tube rises. On the other hand, if the angle is more than 90°, the level of water in the tube goes down. In the case of water and the cloth, the angle of contact is nearly zero, so the water goes readily inside to wet it. The angle of contact between the water and the wax is about 107°. So when some wax is rubbed on the cloth, the water first comes in contact with the wax and the angle of contact being more than 90° it does not enter the cloth. So the cloth becomes waterproof. |
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