As the remnants of Hurricane Isaac dropped lots of much needed rain on our drought stricken area last week, our minds were on water. Drops of rain stuck to the window. Streams of water rushed through yards making new trenches. The visible power and properties of water created lots of questions. So, we experimented and investigated. In today’s Lab Report, sponsored by Apologia Science, we’ll experiment with the surface tension and cohesion properties of water.
This is one of the kids’ favorites. We had to do it again and again. http://youtu.be/BQdL4_ZLMj4
The surface tension of water is cause by cohesion. Cohesion means that the water molecules like to stick to each other. This is caused by the slightly negative charge of the oxygen atom of one water molecule being attracted to the slightly positive charge of the hydrogen atoms of another water molecule. You can, also, test the cohesion properties of water using an eyedropper, water and a coin. Slowly, drop water onto a coin. Watch as the drops of water stick together to form a larger drop.
The water molecules will stick together and form a dome over the coin. Keep adding drops until the drop breaks and spills off of the coin. This is caused by gravity overcoming the force of the cohesion. How many drops of water can you fit on a coin?
For Further Experimenting
You can explore the properties of liquids and download FREE lab sheets.
Have you seen the new General Science Notebook from Apologia? A great edition to the Apologia General Science Course!