Introduction: A Better Way to Test Surface Tension

One day in Chemistry class, I would be working with the properties of a liquid which includes surface tension. When I got home, I decided to try to see how surface tension changes depending on the chemical makeup of the liquid. To test this I made a solution that was 50% water and 50% sugar (by weight). I then boiled it to a syrup and saw that surface tension did change. The original way of seeing the strength of surface tension is to put a drop on a coin. This works to a certain extent, however it is not precise and will not actually show you how strong the surface tension is without filling up the entire coin.

Step 1: My Upgrade to the Coin

My fix for this was to make small bowl, around 5mm in diameter with a small ridge along the edges. Because of this edge, the liquid has a barrier so you can use less of your desired liquid and be more able to see the surface tension. To use the small bowl you add small amounts of liquid until the top of the liquid is past the ridge. After this point you add small amounts of liquid and keep measuring until a point where the surface tension breaks.

Step 2: How to Create My Fix

This particular model that I created was made from a 3D printer, however it can be made using any waterproof material such as metal, glass or plastic. The basic design is a flat base with a ridge going along the edge that is about 1/10 the diameter. This model shown in the photo above is about 5mm in diameter, however it can be made in different sizes depending on how much liquid you are willing to use to measure the surface tension.

Step 3: How to Calculate Water Tension

After you find the point right before the surface tension breaks, you can preform this formula to find the Surface tension T=F/L where T is Surface Tension, F is the Force being pushed on your liquid per unit length and L is the Length over which the force acts. Surface Tension then is measured in Newtons per meter. For example the Surface tension for water is 72 dynes/cm at 25°C and the Surface Tension of Mercury is 438.4 dynes/cm at 12.5°C.