LAB: Properties of Water
Name________________________________
OBJECTIVE: Upon completion of this lab, you will:
• Demonstrate knowledge of the structure of water
• Have an understanding of the importance of hydrogen bonding
to the properties of water
Water is the most important chemical compound to living things. The things that make water
such a great compound for life are:
1. It is polar: Water has both a positive and a negative charge on its molecular structure.
This enables it to dissolve almost anything. Contrary to popular belief, water is not a
universal solvent, as it is unable to dissolve nonpolar molecules such as fat.
2. It forms hydrogen bonds: These weak bonds that collectively are very strong make
possible most of water’s unique properties, such as cohesive and adhesive properties, high
specific heat, high heat of vaporization and polarity.
3. It has a high surface tension: Because of the hydrogen bonds that hold water
molecules to each other, this creates a ‘net’ of water molecules that allows some
organisms to walk on water, such as water striders.
4. It has a high heat capacity: This is a good thing for all living things because if it only
took a short amount of time for water to heat up, animals and plants would boil in the
heat of the sun…not a good thing for us here in southern California!
5. It has a high heat of vaporization: This is important because many organisms use
evaporative cooling; or the evaporation of water, in order to cool themselves off when
they are hot.
6. It is less dense as a solid than it is as a liquid: This is essential to organisms that live
where it is always cold. The ice floating on top of bodies of water provides insulation for
the life below and prevents organisms’ bodies from freezing solid in the winter.
You and your partner will do several activities to explore the properties of water.
MATERIALS:
Water
Penny
Ethanol
Soap solution
Small plastic cups Sugar
Droppers
Mineral oil
Glass microscope slide Piece of wax paper
Salt
Ice
2 small beakers
Fan
Balloon
Water Models
SAFETY: Alcohol is flammable and toxic, keep away from sources of heat.
Also, dispose of alcohol as your teacher directs.
Activity 1: Water’s Molecular Structure and Hydrogen Bonding
1. Using the molecular models provided for you by your instructor, sketch a model of water.
Give a description of the shape of the water molecule.
2. Now, using your model, draw what hydrogen bonding of multiple water molecules looks
like.
Station 1: High Heat Capacity
Get 2 small beakers and pour 20 mL of water in one. In the other small beaker, pour
20 mL of alcohol. Place both beakers in a tray with some ice for 5 minutes. You will need
to measure the temperature of each liquid every minute for 5 minutes. Record your data
in an appropriately constructed chart below:
QUESTION: What do you notice about the temperatures of each liquid during this
activity? Why do you think this happens? Use your knowledge of the properties
of water to help you answer this question.
Station 2: Cohesion
Get a penny. Using a dropper, find out how many drops of water you can get to stay on the
head of the penny. Repeat this test 2 more times and determine the average number of
drops your penny is able to hold.
Test #1 ______ Test #2 ______ Test #3 ______ Average ______
Now repeat the experiment using ethanol. Keep the droppers separate!
Test #1 ______ Test #2 ______ Test #3 ______ Average ______
Now repeat the original experiment with soapy water. Keep the droppers separate!
Test #1 ______ Test #2 ______ Test #3 ______ Average ______
QUESTION: How much does the number of drops the penny can hold for each solution
change? Why do you think this happened?
Station 3: Polarity #1
Using a set of small cups, mix some salt and water in one cup, and salt and alcohol in
another. Does the salt dissolve? Describe the results:
Repeat this experiment with a small amount of sugar and water in one cup, and sugar
and alcohol in another. Does the sugar dissolve? Describe the results:
QUESTION: In what liquids do the salt and sugar dissolve, and why? Use your
knowledge of the properties of water, and the results of the previous activity to
help you answer this question.
Station 4: Polarity #2
Using the dropper, form a small puddle of water (about the size of a dime) on a piece of
wax paper. Place the tip of the dropper in the center of the puddle and slowly drag the
tip of the dropper around the wax paper. Record your observations:
Repeat this procedure for the glass microscope slide. Record your observations:
QUESTION: Why does the water behave differently as it is dragged across the wax
paper and across the glass slide? Use your knowledge of the properties of water to
help you answer this question.
Station 5: Polarity #3
Using a second set of small cups, place a small amount of water in one and a small amount
of alcohol in the other. Put a small drop of oil in each cup and observe what happens to
the drop. Record your observations:
QUESTION: In what liquids does the oil dissolve, and why? Use your knowledge of the
properties of water to help you answer this question.
Station 6: Polarity #4
Inflate a balloon. Gently rub the balloon against your clothing, or on top of your head to
create static electricity. Using the faucet at a sink, turn on the water so that a slowly
running stream of water exits the faucet. Bring the balloon close to the stream of water
but do not allow the balloon to touch the water. Record your observations:
QUESTION: Why does the water behave as it does? Use your knowledge of the
properties of water to help you answer this question.
Station 7: High Heat of Vaporization
Get a piece of sponge and rub some water on the inside of your forearm. Place your
moistened arm in front of a fan, and time how long it takes in seconds for the water to
completely evaporate so that your arm is dry.
Repeat this activity with an alcohol swab.
QUESTION: Which liquid appears to dry faster, and why? Use your knowledge of the
properties of water to help you answer this question.
CONCLUSION: After performing all the activities in this lab, write a conclusion
paragraph (at least 5 sentences!) that describes why the properties of water make it a
necessary molecule for most living things on our planet. Choose TWO properties of water
from the list on the first page, and be very specific about how those properties help
support life.