A meniscus is a curve in the surface ar of a molecular substance (water, the course) as soon as it touches another material. V water, you can think of it as once water sticks to the within of a glass.
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What is a meniscus?
A meniscus is a curve in the surface ar of a molecular problem (water, the course) once it touches an additional material. With water, you can think of it as when water sticks come the inside of a glass.
Why a meniscus occurs
Adhesion is responsible because that a meniscus and this needs to do in component with water"s fairly high surface tension. Water molecules space attracted to the molecules in the wall surface of the glass beaker. And also since water molecules prefer to pole together, once the molecules poignant the glass cling come it, various other water molecules cling come the molecules poignant the glass, developing the meniscus. They"ll take trip up the glass as much as water"s cohesive pressures will allow them, till gravity stays clear of them from going further. Cohesion is an intermolecular attraction between like molecule (other water molecules in this case).
Sad story of a meniscus misread
Few civilization take the moment to think about the importance of water menisci in their lives. But, imagine this chilling scenario:
In her high-school chemistry final exam you mistakenly read a meniscus together 21.9 milliliters (ml) rather of the exactly 21.7 ml (in this picture), and also thus you get an 89 ~ above the test rather of a 90. Your GPA drops from 4.00 to 3.99 and also you don"t get into that engineering college regime you wanted. Consequently, you don"t get that prestigious engineering job, where, twenty years later, you would have invented a brand-new water-based chemical to permit rubber to grip better. Sadly, 10 years later, a mother and also her adorable 4-year old daughter room leaving the ice cream cream store and also the small girl, whose shoes don"t have your un-invented coating, slips top top a napkin and also drops her ice cream cone. She cries at her loss ... Due to the fact that you misread the meniscus in the 12th grade.
The moral of this fictional story is that it is crucial to check out the measure up correctly, and also yes, in the picture above, the true volume in the graduated cylinder is at the bottom of the water level—21.7 milliliters, not 21.9.
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"Upside down" meniscus
As this snapshot shows, a meniscus have the right to go up or down. The all counts on if the molecule of the liquid are an ext attracted come the outside material or to themselves. A concave meniscus, i m sorry is what you normally will see, occurs when the molecules of the liquid space attracted come those of the container. This occurs v water and a glass tube. A convex meniscus occurs as soon as the molecules have actually a more powerful attraction to each other than come the container, just like mercury and glass. A flat meniscus wake up with water in some varieties of plastic tubes; pipe made out of material that water does no stick to. In any case, you obtain the true volume the the liquid by reading the facility of the liquid in the tube, which will certainly the lowest vertical point of the liquid.