How Does Liquid Measurement Work?

How Is Liquid Measurement Different?

Measuring liquids can be more difficult than measuring solid substances because of the surface tension of the liquid. Gravity pushes down on the surface of a liquid, but at the edges of the container the surface tension of the liquid pulls it gently up the sides. Therefore, the top of the liquid is not flat, but has a convex shape that is often difficult to measure when the volume of liquid you are measuring is relatively small.

Finding the Meniscus

To accurately measure a liquid, it is important to locate the meniscus, which is the lowest part of the convex shape that the liquid makes in the measuring vessel. It is also important to have the surface of the water at eye level. If you are looking at the liquid from slightly above or below, the position of the meniscus will shift slightly and give an inaccurate reading.

Adjust the Volume

Locate the line that marks the measurement you wish to take. Hold the vessel at eye level and locate the meniscus. Add or remove liquid as needed with a dropper or something that can add or subtract small volumes from the container. Do this until the level of the meniscus is level with the line of the desired volume.

If You Fail

Failing to locate a meniscus may indicate that the vessel you are measuring in is dirty and unable to hold the surface tension of the liquid. Alternatively, different types of liquids have different surface tensions and, therefore, different meniscuses.