WLHS / Bio
Name
A Series of Water Labs
Directions: Complete all of the mini-labs described below. Where indicated, record observations, sketches, etc.
Upon completion of all mini-labs, answer the post-lab questions.
Lab 1: Surface Properties of Water
Materials: 250 mL beaker, beaker, paper clips, toothpicks, dish soap.
1) Fill the 250 mL beaker about half full with tap water.
2) Carefully float a paper clip on the surface.
Q: Which is more dense, paper clips (metal) or water?
Q: How is it possible that a paper clip can float? (give the scientific/chemical explanation)
Q: Can you float more than one paper clip on the surface?
How many can you float?
3) Dip the end of a toothpick into some dish soap.
4) Dip the end of the toothpick into the beaker so that it touches the edge of the water surface.
Q: What happens?
Q: What is the scientific explanation for this?
Lab 2: Surface Properties of Water
Materials: staples, petri dish, oil soap, pipettes, paper towel
1) Fill the two halves of the petri dish with water.
2) Float a single staple on the water in one dish – add oil drop near side of the dish.
3) Float a single staple on the water in the second dish – add a drop of soap solution near the side of the dish.
Observe both dishes.
OBS: Record your observations of both dishes
Dish 1 (OIL):
Dish 2 (SOAP):
Q: Based on what you know about water (surface tension, etc.), explain what you saw.
4) Clean the petri dishes with brush & soapy water. Dry with a paper towel.
Lab 3: Cohesion of Water
Materials: waxed paper, water, pipette, liquid soap & toothpick.
1) Place a drop of water on 2 different places on the wax paper.
2) Add soap to one drop using a toothpick.
OBS: Record your observations of the two drops.
Sketch the shape (from the side) of the two drops.
-DROP 1 (WATER ONLY):
-DROP 2 (WATER & SOAP):
Q: Based on what you know about water, explain what you observed.
3) Throw used wax paper and toothpick in trash.
Lab 4: Drops on a Penny
Materials: 2 pennies, 2 pipettes, beaker of water, beaker of detergent water.
1) Predict the # of drops of water that will “fit” on one penny.
PREDICTION:
2) Test your prediction. Record the # of drops that “fit.”
# of DROPS:
OBS: Record observations of water on penny. Be sure to observe the penny from all angles.
Q: What is the explanation for this phenomenon? (Use the concept of polarity in you’re answer)
4) Predict the # of drops of DETERGENT WATER that will fit on one penny. PREDICTION:
Q: Is this different from you prediction in step one? Why or why not?
5) Test your prediction.
Q: How many DROPS DETERGENT WATER fit?
Q: Explain your results using the concept of polarity.
Post-Lab Questions
1) What is a polar bond?
2) What phenomena observed in this lab is evidence that water contains polar bonds?
4) Based on your results, does oil contain polar or nonpolar bonds? Explain.
5) Based on your results, does soap contain polar or nonpolar bonds? Explain.