The Meniscus

	Normally, liquid will curve at the edges of the surface where the liquid touches the container because water molecules are more attracted to glass than to each other.  This curvature is called the meniscus. We need to read the level at the bottom of the meniscus to measure a volume of liquid in a graduated cylinder.
	There are some materials where the curve goes up. In this case, we read the top of the meniscus.
	In some plastic cylinders water has a flat surface. In that case, we use the centre rather than the edges.
	The visibility of the meniscus can be enhanced by using a card with a dark stripe and placed behind the cylinder.  Then, adjust the placement of the card to give us either a white meniscus against a black background or a black meniscus against a white background.
	We need to read the meniscus at eye level in order to get an accurate reading and if we see the liquid slightly above or below, we may find a little shift in the meniscus and get inaccurate readings. We should place the graduated cylinder on the table and then lower their heads to be able to read the meniscus at eye level.

	Videos on how to measure volume using graduated cylinder at http://www.youtube.com/watch?v=iPkZlce84ag
	Additional explanation and some exercise on measuring volume using graduated cylinder at http://www.wisc-online.com/objects/ViewObject.aspx?ID=gch302