Name: _____________________________________
Block: ________
Date: ________________
Properties of Water Lab
Objective:
To explain how water behaves & how water relates to our bodies and the environment.
Background Information:
Water covers approximately 75% of the surface of the earth. Water is a simple molecule, but the most
important molecule for living systems. Water makes up between 50%-95% of the weight of organisms. We
often say that water makes up about 75%, but this varies among species.
As you will learn from our class notes, water has some very unique properties that make it useful and
critical to all living organisms. Most of these interesting properties are due to the fact that water molecules
are polar and, thus, attracted to each other like small magnets. The attraction of one water molecule to
another is called cohesion. Cohesion results because the oxygen end of a water molecule has a slightly
negative (-) charge while the hydrogen end has a slightly positive (+) charge.
Safety:
Because we are working with glassware, you will need to wear safety goggles and closed toed shoes.
Materials:
 Water
 Oil
 Hand soap
 1 dry penny
 1 graduated cylinder
 2 dropper pipettes
 2 test tubes
 A test tube rack
 Food coloring
Pre-Lab Questions:
1. Compare and contrast adhesion and cohesion.
2. What is surface tension?
3.
Draw a water molecule using Bohr models to show the covalent bonds that occur between oxygen
and hydrogen atoms. Label each end in terms of its polarity.
Procedure:
Please READ through ALL procedural steps BEFORE GETTING STARTED. I will
only answer questions about the procedure before you start working.
Part A:
1. Label two pipettes using masking tape and a pen—label one “water” and the other “oil”
2. Using your prior knowledge of the size of a droplet, predict how many drops it would take to fill 1 ml.
Record your prediction in Data Table 1.
3. Using the water pipette, drop water into the graduated cylinder carefully, counting each drop.
4. Count how many drops from the pipette make up 1 ml.
5. Record the actual number of drops required to fill 1 ml in Data Table 1.
Part B:
1. Place a clean, dry penny on the lab bench.
2. Predict the number of droplets that the top surface of the penny will hold before spilling over the
edge onto the lab bench.
3. Carefully add one drop of water at a time to the penny’s surface using your water pipette.
4. Count the number of drops as you add them.
5. In Data Table 1, record the actual number of drops added to the penny BEFORE the water spilled
onto the lab bench.
6. Be sure to draw and label an aerial (bird’s eye) view and a cross-sectional (side) view of your penny
with the water on it. Draw in the area labeled Part B Drawings.
Part C:
1. With a paper towel, dry off your penny completely.
2. With one finger, thinly spread one small drop of soap onto the surface of your penny.
3. Predict the number of drops that your soapy penny will hold before spilling over onto the lab bench
and record your prediction in Data Table 1.
4. Carefully add one drop of water at a time to the penny’s surface using your water pipette.
5. Count the number of drops as you add them.
6. In Data Table 1, record the actual number of drops added to the penny BEFORE the water spilled
onto the lab bench.
7. Be sure to draw and label an aerial (bird’s eye) view and a cross-sectional (side) view of your soapy
penny with the water on it. Draw in the area labeled Part C Drawings.
Part D:
1. Using the graduated cylinder, measure 5ml of water then pour it into one of the test tubes
2. Using the pipette labeled “oil”, gently add 2 ml of oil to the same test tube by tilting the test tube
slightly and dropping the oil onto the side of the test tube, allowing it to run slowly down the side of
the test tube. (Use your data from part A to know how many drops 2 ml would be).
3. Record your observations in Data Table 2.
Part E:
1. Because the oil does not come out of the graduated cylinder easily, I ask that you measure 5 ml
of oil with the dropper pipette. If you get oil in my small graduated cylinder I will take off
points. Drop the 5 ml of oil into the un-used test tube using the oil pipette. Using the water pipette,
gently add 2 ml of water to the same test tube by tilting the test tube slightly and dropping the water
onto the side of the test tube, allowing it to run slowly down the side of the test tube. (Use your data
from part A to know how many drops each ml would be).
2. Record your observations in Data Table 2.
Part F:
1. Use your knowledge of water and oil to make some predictions about what you think would happen if
you added a couple drops of food coloring to each of your test tubes. You do not need to record these
predictions.
2. Add 1 or 2 drops of food coloring to each test tube (the ones from Parts D & E).
3. Give the food coloring time to disperse and watch the process—it’s pretty cool!
4. Record your observations in Data Table 2.
Data Table 1:
Predicted Number of Drops
Actual Number of Drops
Part A:
Part B:
Part C:
Data Table 2:
Observations
Part D:
Part E:
Part F:
Part B Drawings:
Part C Drawings:
Further Analysis Questions:
Please type the answers to the following questions on a separate piece of paper and turn them in on
the due date.
1. Use the terms adhesion and cohesion to explain your results for Part B.
2. Did smearing the soap onto the surface of the penny affect how many drops of water the penny could
hold? Given the previous response, what effect does soap have on water molecules?
3. Regarding Parts D & E, thoroughly explain what happened when you mixed the oil and the water.
4. Regarding Part F, how did the food coloring react when it was added to each of the test tubes from
Parts D & E? Did it mix with either liquid?
5. What do the words hydrophobic and hydrophilic mean?
6. Given what you observed regarding soap and water (Part C), what do you think happens when soap
runs off into a water body (like a lake or a river)? What do you think could happen to the surface
tension of the water? What might happen to organisms that rely on water’s surface tension? Why
would you care about those organisms?
7. Do you think it is important for us to be more conscientious about the amount of soap we use
(showering, washing dishes, brushing teeth, washing cars, etc)? Explain why or why not.