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For starters, water doesn’t wet everything. “There are very wet things, like paper. Others less so, like glass (it gets wet but doesn’t soak) and some that simply don’t get wet, like some types of plastic”, says chemist Watson Loh, from Unicamp. What determines the ability of water to wet or not is the intensity of its interaction with other substances. A very strong characteristic of the water molecule is that it forms poles, as if they were small magnets. When other substances have the same characteristic, they interact with water and wet it – this is the case with cotton and paper. Molecules in glass and metal also form poles of attraction, but neither gets soaked because they are smooth solids and do not absorb water. Plastic, on the other hand, because it is made of carbon and hydrogen molecules, has no poles. Water does not have as much affinity with this substance and prefers to stay in it.
It’s not wet, no!
When we put a drop of water on a plastic, the liquid forms an almost round droplet, which drains easily. In addition to not having poles to interact with water, the plastic is very smooth
WETABLE SUBSTANCES
Cotton and paper, for example, get soaked with water. In addition to having poles that interact with water as if they were magnets, they are composed of fibers full of holes where water can settle.
“WETABLE MEDIUM” SUBSTANCES
Did you know that our skin doesn’t have poles to interact with water? If that happened, we would dissolve in the rain or in the pool! But, as our skin is full of tiny holes, then a little water is deposited in these spaces