It is called the meniscus , but let me give you some more information on the subject. A meniscus is the curved surface at the top of a column of liquid. In a science class, this liquid is usually water or some sort of aqueous solution, and the column is usually a graduated cylinder or a pipet.
As you may have noticed, when water is in such a thin glass tube, it does not have a flat surface at the top. Instead, the top is curved inward, making it a little difficult to decide exactly where to read the volume. Why a meniscus occurs Water molecules are attracted to the molecules in the wall of the glass beaker.
And since water molecules like to stick together, when the molecules touching the glass cling to it, other water molecules cling to the molecules touching the glass, forming the meniscus. All pipets are calibrated to the lower meniscus , so use it as long as you can see it.
If the solution is very dark or opaque to the extent that the lower meniscus is not visible, only then use the upper meniscus. In the case of liquids like mercury that form a convex meniscus , use the top of the convex meniscus. A meniscus occurs because of surface tension in the liquid and must be read at eye level. For a concave meniscus , the correct volume will be read at the bottom of the curve.
For a convex meniscus , the opposite is true and the correct reading will be at the top of the curve. Graduated cylinders are designed for accurate measurements of liquids with a much smaller error than beakers. They are thinner than a beaker, have many more graduation marks, and are designed to be within 0. Therefore, this more precise relative of the beaker is just as critical to almost every laboratory. Measure so that the line you are reading is even with the center of the meniscus.
For water and most liquids, this is the bottom of the meniscus. For mercury, take the measurement from the top of the meniscus. In either case, you are measuring based on the center of the meniscus. Record the final volume of the burette as final burette volume to 2 decimal places. Go and weigh the 50 ml beaker again with the water in it.
Record the mass for the 50 mL beaker plus water. The meniscus plays a vital role in maintaining the stability of the knee joint along with optimizing the tibiofemoral load transfer and distribution. This also helps in preserving the health of the articular cartilage. Sep 22, For aqueous solution you speak of the "meniscus".
Explanation: For volumetric glassware, we line up the graduation with the lowest point on the meniscus. See this site. Related questions How can accuracy of a measurement be improved? How can percent error be reduced? How can precision be improved? The liquid appears to "stick" to the edge of the container.
Most liquids, including water, present a concave meniscus. A convex meniscus sometimes called a "backwards" meniscus is produced when the molecules of the liquid are more strongly attracted to each other than to the container.
A good example of this shape of meniscus can be seen with mercury in a glass container. In some cases, the meniscus appears flat e. This makes taking measurements easy.
When you read a scale on the side of a container with a meniscus, such as a graduated cylinder or volumetric flask , it's important that the measurement accounts for the meniscus. Measure so that the line you are reading is even with the center of the meniscus.
For water and most liquids, this is the bottom of the meniscus. For mercury, take the measurement from the top of the meniscus. In either case, you are measuring based on the center of the meniscus. For a flat meniscus, make sure the liquid is level.
Usually placing the container on a lab bench does the trick.
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