It is a common saying that water is a terrible lubricant. But, if you apply water to certain materials like glass, ice, soap, or tile, that surface becomes slippery when wet.
So what is the difference between a true lubricant, and something like water, which makes things slippery?
In: Chemistry
Lubricant reduces the friction between two surfaces particularly jn “tight” contact—makes surfaces slide against each other easier under higher pressure. Think flush metal against metal. I would say it’s not incorrect to say lubricated surfaces are also “slippery” although in connotation slippery might refer to “slides with very little force” and lubricated might mean “slides but needs a little force”.
Water is slippery for surfaces that are not in tight contact. Think your feet on a slip-n-slide or your car on ice. As it, is these surfaces didn’t need a lot of force to slide against each other even without the water because they were free and loose against each other. Of course lubricant would also make your feet or your car slide very easily so you can say it is slippery.
If the product is on a motor shaft, it’s lubricated. If it’s on a doorknob, it’s slippery.
Eli5
The distinction is strictly language.
When a physical object is _slippery_ the description is without intent or judgement. When an object is _lubricated,_ the implication is that the object _should_ be slippery, often for proper functioning. One expect ice to be slippery, while machinery may require lubrication to work as intended. Water is absolutely the “lubricant” on a water park slide but can result in rust when exposed to (say) iron. A lubricant would be formulated not to damage whatever it’s used for.
There isn’t really a difference. To “lubricate” something means to make it more slippery. So anything can act as a lubricant, as long as it performs that job.
The confusion is with your basic assumption: that water isn’t a lubricant. Water *can* make things slippery, where it does a good job as a lubricant. For other things it doesn’t do a good job. One common example is human skin. Our skin has a lot of oils in it, which is why you feel “greasy” if you haven’t taken a shower in a while. Water can remove these oils, making your skin *less* slippery.
That’s a pretty common problem with water, which is why it doesn’t always work well as a lubricant. Better lubricants, like fats and oils, don’t really interact with anything, and just fill in all the tiny nooks and crannies. This is what makes the surface smooth, or “slippery.”
The Teflon on your frying pan is slippery, the butter between your pan and the pancakes is a lubricant
Lubricant implies the presence of a fluid between the two surfaces, but surfaces like ice, glass, Teflon can be slippery even when dry.
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