Biology Lab for virtual school.. Lesson 1.04

Topics: Water, Surfactant, Soap Pages: 4 (783 words) Published: October 19, 2013
 T’Chaya Richardson October 19, 2013

Lesson 1.04
Properties of WATER

Problem Statement:

What effect will adding soap to water have on surface tension?


When an object falls onto the surface, it has to push the water molecules apart. If the effect of the weight of the object is insufficient to match the attractive forces between molecules in the surface layer, the object will not enter the surface.

Molecules of most detergents and soaps are long chain hydrocarbon molecules with an ionic group at one end, usually carrying a negative charge, thus making it an anion.

When the drop of detergent is added to the powdered surface, the initial effect is to draw the powder back to the edges very rapidly as the detergent molecules form their own surface layer with a lower surface tension than the water. As the detergent gradually mixes with the water, the powder begins to sink, and a needle will now pass through the surface with ease under its own weight. However, the calcium and magnesium salts of many detergent molecules are soluble, so detergents still lower the surface tension of hard water


If you add soap to water, than it will decrease the effect on the surface tension.


Control: Is the tap water
Independent Variable: Is the soap
Dependent Variable: Is the drops of soap you fit on the penny

1. I received a beaker filled with tap water.
2. I took a pipette and filled it up with water from the beaker. 3. I began...
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