A drop of water on a non absorbant surface looks like a perfect circle. Why does it look this way? What would happen if a small amount of detergent was added?
This is a cohesion and adhesion lab, but I just can't see how it's related.
Thanks,
2007-09-26 11:42:20 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Biology
The drop looks like a circle because water molecules stick to each other. This gives the water droplet surface tension and holds it together in the smallest shape possible - a circle.
Adding detergent breaks the surface tension, so the water molecules don't stick together well. The drop of water spreads out on the surface.
2007-09-26 11:51:34 · answer #1 · answered by ecolink 7 · 0⤊ 0⤋
OK. Got this. I just learned it. 100 on the test and everyone else failed! yeah, I am that good! Cohesion-single substance joined together by chemical bonds. Adhesion-more than one substance joined together by chemical bonds. So, the drop of water stays together by cohesion. The water molecules- single substance. Hydrogen bonds hold the water molecules together.This is cohesion! Now, when you add detergent, that is a different substance. It is a base with a pH more than 7. When you add the detergent, it breaks the hydrogen bonds down. Example- cup of water filled to the top. You can add so many pennies to it due to cohesion. The top of the water bulges out but it does not drip. That is because cohesion is holding the water molecules together. The hydrogen bonds are holding the molecules together. Now, different cup of water. Add soap or detergent in your case. You can only get a few pennies in the water. There is no more cohesion because you added another substance. The soap broke down the hydrogen bonds. I hope you get this. Read my answer a few times and try the experiment. It will help you understand a lot better. read your book too. Email me if you have more questions. I can help!
2007-09-26 19:03:14 · answer #2 · answered by Anonymous · 1⤊ 0⤋
the surface tension of water is constant throughout its' area .. when you add detergent, IF you don't agitate it and spread the detergent throughout the drop of water you will get an uneven surface tension and the water will capilliarate in various areas, depending on the surface construction of the article you put the water drop on
2007-09-26 18:56:01 · answer #3 · answered by The old man 6 · 1⤊ 0⤋