Cohesion is the “stickiness” of like molecules to one another. When we fill the glass with water, we notice right away that it can go over the brim of the glass without spilling. The higher the surface tension of the water, the bigger a droplet you can make before it breaks and flows over the edges of the penny. Fill the dish with milk. The surface tension was not strong enough. More on variables here This holds the surface molecules together and holds the water in place over the coin, stopping water spillage for much longer than you would expect. Things that reduce surface tension are called surfactants. What's Going On? MOBILE, Ala. (WKRG) – In today’s Science Corner experiment, see how surface tension works in two different experiments! Surface tension and cohesion is the reason you can get so many drops of water on a penny. Magic Milk Surface Tension Experiment . (*Whole milk works best due to its higher fat content. Surface tension is a special term we use to describe the cohesion between water molecules. In this case, the like molecules are the H20 molecules in the water drops. That magic is the surface tension of water. Set up a row of coins and add different colors of water drops to each, forming surface tension. These experiments can be performed easily anywhere with simple materials. They are attracted to one another, and the force of attraction creates surface tension. Use a toothpick to pull water from the first coin to the second coin. by: Ron Perkins. Surface Tension: Even though aluminum has a density of 2.7 gm/cm 3, and the density of water is 1 g/cm 3, aluminum yen coins can float on the surface … Now, add the coins one at a time to the glass of water, dropping them in rim-first (not face down). Water and Surface Tension. Water molecules like to stick together. There are two properties at work in this experiment: cohesion and surface tension. Fill a clear glass with water all the way to the brim. Because of surface tension, liquid surfaces act like a kind of ‘skin’, able to support small insects and materials on their surface. Water molecules love to stick together! Variables to test. Next try the classic surface tension experiment of floating a sewing needle on top of the water. In this project, you will put droplets of water on a penny, like in Figure 1. Guess how many coins you can add to the glass before the water starts to overflow! To make it easier, place a small piece of the paper towel on the water first, and then place the needle on the paper towel. Squeeze or pour a small amount of dish soap into a small bowl. Add water around a coin on a plate. Can you pull the water all the way to the end of the row of coins without breaking the tension? One using a penny and the other using dish soap to propel a cardboard boat! 10-12 coins of the same size Method: 1. Frugal Fun for Boys has a great surface tension investigation using a coin and different liquids! Some preschoolers may want to understand the magic behind this simple science with coins. This means you need to reduce the surface tension of water. Who knew that a single coin could be used for so many classroom science activities! You can use washing up liquid’s power of disrupting the surface tension of water to race lolly sticks. Surface tension experiments can be a fun way to learn about the unique properties of water. Surface tension is the result of all the water molecules sticking together. Can a surface tension experiment result in some cool action art? You’ll notice that the water hangs slightly over the top of the glass but doesn’t spill out just yet. More Surface Tension Experiments for kids. Drop food coloring onto the milk in various spots. Cohesion is the attraction of like molecules to one another. However, 1% or 2% milk will work in a pinch.) 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