glass of water
metal paperclip
Hydrogen Bonding of Water
012-10993 r1.04
glass of water
metal paperclip
Hydrogen Bonding of Water
012-10760 r1.04
Hydrogen Bonding of Water
Introduction
Journals and Snapshots
The Snapshot button is used to capture the
screen.
The Journal is where snapshots are stored
and viewed.
The Share button is used to export
or print your journal to turn in your
work.
Each page of this lab that
contains the symbol
should be inserted into your
journal. After completing a
lab page with the snapshot
symbol, tap
(in the upper
right hand corner) to insert
the page into your journal.
Note: You may want to take a
snapshot of the first page of
this lab as a cover page for
your journal.
Hydrogen Bonding of Water
Lab Challenges
• Why is water such an important molecule in nature and earth
science processes?
• What gives water its unusual properties? For instance, how
can a metal paperclip float on the surface of water?
Hydrogen Bonding of Water
Background
Water has many unique properties. These
properties are derived from water's ability to
hydrogen bond to neighboring water
molecules. This happens because water is a
polar molecule meaning it has a positive (+)
side and a negative (-) side.
Note: In H2O, more electrons surround the
oxygen atoms than the hydrogen atoms, so
the oxygen side of the molecule has a slightly
negative charge, and the hydrogen side has a
slightly positive charge.
Hydrogen Bonding of Water
...Background
• The imbalance in charge makes water molecules
attract each other like tiny magnets.
• In a sense, water likes to "stick" to itself. This
gives water a high surface tension, hence its
tendency to bead up on surfaces and even
support the weight of small insects (and even
paperclips!)
• During phase changes, energy added to water
must go into breaking or forming the hydrogen
bonds before the water can heat up or cool
down. This is called latent heat.
Hydrogen Bonds
• The latent heat of
fusion is the energy
required to freeze or melt
water. The latent heat of
vaporization is the energy
required to boil or
condense water.
Hydrogen Bonding of Water
Self-Check
1. Water molecules are able to "hydrogen bond"
together because water is a _______ molecule.
a) diet friendly
b) covalent
c) ionic
d) intermolecular
e) polar
Hydrogen Bonding of Water
Self-Check
2. The energy required for the latent heat of fusion
in water would go into
a) melting ice to water
b) freezing water to ice
c) boiling water to vapor
d) increasing the temperature of water
e) both A and B are correct
Hydrogen Bonding of Water
...Background
• Water's unusual properties makes it important to many earth science
processes. E.g., the polar nature of water allows it to wet surfaces of rocks,
clays, and soil, drawing water deep into cracks and crevices and contributing
to important erosion processes.
• Water naturally dissolves and reforms minerals and salts, carrying nutrients
through the biosphere. "Mineral water" contains dissolved metals and salts
important to your health!
• Conversely, several important molecules like carbon dioxide and oxygen can
dissolve into polar water, allowing for life beneath the waves. Fish need
oxygen molecules to survive—they just extract it from the water (using gills),
whereas humans extract oxygen from the air using lungs.
Hydrogen Bonding of Water
Self-Check
3. What kinds of important molecules can dissolve
into water?
a) carbon dioxide and oxygen
b) oxygen and sucrose
c) proteins and methane
d) lipids and carbon dioxide
e) Hot cocoa and marshmallows
Hydrogen Bonding of Water
Background
• The polar attraction between water molecules gives water a higher heat capacity
(resistance to temperature change) than most other substances. This high heat
capacity moderates climates near oceans and lakes and helps organisms moderate
their own temperatures. You can grab a hot pot handle briefly and not get burned,
because the water in your skin cells resists temperature change.
• Hydrogen bonds require water to reorganize into a honeycomb shaped matrix
when it freezes. The molecules in ice occupy more room than an equal amount of
liquid water. This makes ice less dense than water, so it floats. It also makes water
expand when it freezes. Water that squeezes into cracks and freezes will pry rocks
Water expands and rises
apart, furthering the erosion process.
as it turns into ice
cubes!
Hydrogen Bonding of Water
Self-Check
4. Tony waves his hand briefly over a campfire but
does not get burned. This is because the water in
his skin cells has a large _________________.
a) volume
b) polarization
c) surface area
d) heat capacity
e) concentration of caffeine
Hydrogen Bonding of Water
Safety
• Wear safety glasses and follow all standard laboratory safety procedures.
• Keep water away from sensitive electronic equipment.
• Handle the hot plate and hot glassware in this lab with care. Do not
touch with bare hands!
• Do not attempt to hold or move a beaker with boiling water. It can easily
spill over causing serious burns.
• Do not allow the wires of the temperature probe to touch the hotplate at
any time.
Hydrogen Bonding of Water
Materials and Equipment
Collect all of these materials before beginning the lab.
• Temperature sensor
• Crushed ice, 300 mL
• Hot plate
• Buret clamp (2)
• Stirring rod
• Small tripod base and rod
• Beaker 1-L
Fill with ice
Hydrogen Bonding of Water
Sequencing Challenge
A. Fill glass beaker
with ice.
B. Start warming the
beaker and insert
temperature probe
to start timed
collection.
C. Find the freezing
and boiling
temperatures from
your graph.
D. Compare heat
needed to melt ice
to heat needed to
warm water to a boil
to heat needed to
evaporate water.
E. Use graph to
explain what the
heat from the hot
plate is doing to the
water molecules.
The steps to the left are part of
the procedure for this lab
activity. They are not in the
right order. Write the correct
sequence below, then take a
snapshot of this page.
Hydrogen Bonding of Water
Procedure
1. Turn on the hot plate, but do not put anything on it yet.
2. Connect the temperature sensor to your data collection system.
3. Fill the beaker with crushed ice (approximately 300 mL).
4. Place the temperature sensor in the ice and begin recording data while slowly
stirring.
5. Collect this data for at least 30 seconds.
Go to next screen while still collecting data.
Hydrogen Bonding of Water
6. When the hot plate is
completely warmed,
place the beaker on the
hot plate and continue
stirring.
7. Stir continuously
throughout the entire
experiment. Partners may
take turns stirring.
8. Be extremely careful not
to allow the Temperature
Sensor to touch the glass
or to leave the surface of
the ice/water.
Go to next screen while still
collecting data.
Hydrogen Bonding of Water
9. Below, note time when it is
obvious that the ice started
to melt. Also, note time
when the water has begun
boiling continuously. Keep
stirring!
Go to next screen while still
collecting data.
Hydrogen Bonding of Water
10.Record data until the ice
has melted completely
and the water has been
boiling for ~10 min. Stop
stirring.
11.Stop the data set
collection.
*To Autoscale the Graph:
1. Tap
to open the tool
palette.
2. Tap
and the graph will
resize itself to fit the
window.
3. Tap
to close the tool
palette
Hydrogen Bonding of Water
Data Analysis
1. Using your graph on the
previous pages, enter the
temperatures where ice
melted and water boiled in
the adjacent data table.
*To Enter Data into a Table:
1. Tap
to open the tool
palette.
2. Tap
then tap a cell in
the data table to highlight
it in yellow.
3. Tap
to open the
Keyboard screen.
Hydrogen Bonding of Water
Data Analysis
2. On a separate sheet of paper, draw your own graph of the experiment. Make
sure to label the overall graph, along with the X and Y axis. Include units on your
axes.
3. Write 5 labels at various data points on your graph. The labels are:
• Heat first applied
• Ice completely melted
• Boiling started
• Region for latent heat of fusion (spans a range of the graph)
• Region for latent heat of vaporization (spans a range of the graph)
Hydrogen Bonding of Water
Analysis
1. Which water could cause a greater burn: 10 grams of boiling water at
100ºC or 10 grams of steam at 100ºC ?
Hydrogen Bonding of Water
Analysis
2. What does the slope of the heating curve of water depend on?
Hydrogen Bonding of Water
Analysis
3. Why doesn’t the freezing point stay constant as the ice melts?
Hydrogen Bonding of Water
Analysis
4. Why doesn’t the temperature of the boiling water move above 100 ºC?
Hydrogen Bonding of Water
Analysis
5. Why does the rate of temperature change when water is melting or
boiling?
Hydrogen Bonding of Water
Analysis
6. Does solid water (ice) have the same heat capacity as liquid water?
Hydrogen Bonding of Water
Synthesis
Use available resources to help you answer the following questions.
1. What are some consequences of water expanding when it freezes?
Hydrogen Bonding of Water
Synthesis
2. Why is it important that water has a high surface tension?
Hydrogen Bonding of Water
Synthesis
3. Why can water act as such a good erosion agent?
Hydrogen Bonding of Water
Synthesis
4. Where does water’s high heat capacity and large heat of vaporization
come in handy for human populations? Give some examples.
Hydrogen Bonding of Water
Multiple Choice
1. A friend wants to heat up ice until it is all
evaporated. When will they have added half the
energy needed to complete the job?
a) Just after the ice has melted.
b) When the water reaches 50° C.
c) Just when the water starts to boil.
d) When half the water is evaporated.
e) None of the above.
Hydrogen Bonding of Water
Multiple Choice
2. Water’s ability to wet some surfaces and not
others is due to the rule that __________.
a) polar molecules attract other polar
molecules
b) water is the universal solvent
c) water will wet all surfaces
d) water always seeks its source
Hydrogen Bonding of Water
Congratulations!
You have completed the lab.
Please remember to follow your teacher's instructions for cleaning-up and submitting
your lab.
Hydrogen Bonding of Water
References
All images were taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons:
http://gallery.hd.org/_c/natural-science/_more2006/_more01/meniscus-on-water-surface-tension-supportingsteel-paperclip-in-drinking-glass-tumbler-beaker-6-AJHD.jpg.html
http://commons.wikimedia.org/wiki/File:Vetysidos.png
http://commons.wikimedia.org/wiki/File:Legameldrogeno-h2o.jpg
http://www.freeclipartnow.com/holidays/ice-cube.jpg.html
http://www.freeclipartnow.com/office/paper-shredder.jpg.html