Water, Water Everywhere!

Biology

9.6.10

Objectives

• To understand the concept of surface tension and the effect of a surfactant

• To understand cohesion and adhesion of water

• To see the hydrophobic, polar and non-polar properties of water

Procedure

• Water in a Penny

• Effects of Detergent

• Glass and Parchment paper

• Water and Oil

• Water, Oil and Coloring

Results/ Data

• Water on a Penny• How many drops from your medicine dropper

are in each cm3 (mL)?• How much water is in each drop? • Predictions: Table of each person’s prediction

of how many drops of water before overflowing on the penny. Include actual data when experiment is complete.

• Draw picture of penny with 1 drop of water, half full, and almost overflowing.

Results/ Data

• Detergent/Surfactant Effects

• Same type of data as “water on penny”

Results/Data

• Glass and Parchment Paper

• Prediction (drawing) of shape of water drop on glass slide and parchment paper

• Drawing of water drop on glass slide and on paper (actual).

Results/ Data

• Water and Oil

• Predict what will happen if you add cooking oil to water.

• Oil will float on top of the water• Oil will sink to the bottom of water• Oil will dissolve in the water• Oil will become mixed up with the water• Something else?

Results/ Data

• Record observations of water and oil in test tube

• Water, Oil and Coloring

• Predict what will happen when a few drops of coloring are added to the oil/water mixture.

Conclusions

• Water on a penny:

• 1. Explain the behavior of the water in the penny in terms of cohesion.

• 2. Did the detergent make a difference on the # of drops that filled the penny before overflow? Describe/Explain. Relate to cleaning agents.

Conclusions

• Glass and Parchment Paper

• Explain the differences in drop behavior in terms of adhesion and formation or absence of hydrogen bonding.

Conclusions

• Water and Oil

• Which is less dense?

• What cause water molecules and oil molecules to separate from one another? (Think polar, non-polar, hydrogen bonding)

Summary