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WATER BASICS: LET'S GET PHYSICAL
MASTER TEACHER Andrea Cantu
GRADES 6-8
OVERVIEW
This lesson provides students with an in-depth understanding of
four physical properties of water (high surface tension, high boiling and
freezing points, high specific heat capacity and density anomaly). During
the lesson students will have hands on experience with surface tension, density
and polarity. The lesson will use video to show how water has unique
characteristics.
ETV SERIES
Simply Science: 105 Water's Structure
Simply Science: 104 Water's Physical
Properties
LEARNING OBJECTIVES
Students will be able to:
* conduct experiments on surface tension and polarity.
* recognize water's molecular structure.
* differentiate between the four physical
properties of water (high boiling and freezing point, high specific heat
capacity, high surface tension, and density anomaly) mentioned in the videos.
MATERIALS
Demonstration
3- 16 oz clear plastic bottle labeled A, B, and C.
1 - bottle of isopropyl alcohol
3- tablespoons of salt
Per student
one activity sheet
one penny
one pipette
Per group of two or three
Internet access
Per group of four
hole puncher
one clear shoe box
one small paper clip
box of large paper clips
one 3x5 inch index card
one crayon of any color
one 4x5 inch sheet of aluminum foil
2-100ml beakers
2- ice cubes
1- 750 ml Erlenmeyer flask
1- 100 ml beaker
1- stopper
35ml vegetable oil
75ml water
VOCABULARY
Anomaly- deviation from the common rule, irregular.
Cohesion - the tendency of different parts of a substance
to hold together.
Compound - two or more elements chemically combined.
Convection current - The circular motion that occurs in a
fluid at a nonuniform temperature due to the variation of its density and to
gravity.
Covalent bonds - atoms sharing valence electrons.
Density - the mass of a substance per unit volume (D =
M/V)
Hydrogen bonds - strong attractive forces.
Molecule - atoms linked by chemical bonds and acting as a
unit.
Phase change - molecules arrange themselves in
distinctly different patterns
Polar molecule - molecule with a negatively charged side
and the other side is positively charged.
Specific heat capacity - the amount of heat needed to
raise the temperature of one unit mass of a substance by one degree Celsius.
Surface tension - the attraction of molecules to
each other on a liquid's surface. Thus, a barrier is created between the air and
the liquid.
Valence electrons - outer electrons.
PRE-VIEWING ACTIVITIES
Pass out worksheets to students. (Note that worksheet activities
and questions are numbered through out pre-viewing, viewing and post viewing
periods.) Each student will be given a penny and a pipette. Students will
drop uniform drops of water on the heads side of the coin. The students
will count and record the number of drops placed on the penny before it
overflows. Dry the penny off and repeat the exercise two more times.
Average the three trials. Have students draw and describe the behavior of
the water on the penny. The videos will provide the students with the
terminology (surface tension and cohesion) used to express the phenomena
the students observed.
FOCUS FOR VIEWING
To give the students a specific responsibility while viewing,
say, "We know that the formula for water is H20 but, how do we know this?
The video will illustrate in two ways how this formula is derived. We know
that a water molecule looks like Mickey Mouse's head. The video will
reveal how the molecular structure of the water molecule gives it some unusual
properties."
VIEWING ACTIVITIES
Say, "In this video clip a hydrolysis experiment,
separating water into its elements, using a Hoffman apparatus will be conducted.
For question #1 record the volume of hydrogen and oxygen collected." Begin
Water's Structure video where there is a lake scene and Dana says, "This
water appears to be still." Pause the tape when Stephanie in a wine
colored lab coat and Darren in a blue lab coat are standing. Darren is
holding a model of oxygen in one hand and two models of hydrogen in the other
hand. Audio is "Two parts hydrogen and one part oxygen, that's
H2O." Say, "What was the volume of the oxygen (9.3 ml) and
hydrogen (18.6 ml)?" Fast forward the tape to when text
appears on the screen which states: Opposite charges attract. Like charges
repeal. The audio is "Science rules." Say, "In
question #2 record the behavior of opposite and like charges. For question # 3
describe why water is attracted to both positive and negative charges."
Resume the tape. Pause the tape where Dana is in the kitchen
holding a model of a water molecule. Dana says, " How do atoms
get electrical charges? Well what are atoms made of?" Say,
"How do opposite and like charges behave? (Opposite charges attract.
Like charges repeal.) Why is water attracted to both positive and negative
charges? (The structure of the molecule causes the attraction to both charges.
Water is a polar molecule.) We have seen that water is a polar molecule.
What happens if we place oil and water together? Pour 75ml of water and
35ml of vegetable oil into your 250ml Erlenmeyer flask. What happened?
Color darkly one side of a 3x5 inch index card with a crayon. Use the hole
punch to punch out 10-12 holes from the index card. Place the holes in the
flask. Put the stopper on the flask and shake the contents. Allow
the contents to settle. What happened?" (Water is polar and attracts
the polar white side of the paper. Oil is nonpolar and attracts the
colored nonpolar side of the paper.
Fast forward the tape to the place where text appears
stating: Atoms sharing electrons. The audio is music. Say,
"Fill in the blank on question #4 do atoms tend towards stability or
instability? In questions 5-8 define the terms." Resume the
tape. Pause the tape where the graphic of a single water molecule
appears. Have students draw a picture of this graphic. Emphasize the polar
structure of the molecule by drawing circles on the TV screen with dry
erase marker around the positive and negative sides of the water molecule. Say,
"We found out that atoms tend toward stability or instability? (Stability)
You just defined six vocabulary words let's go over the words: valance electrons
(outer electrons), covalent bonds (atoms sharing valence electrons), molecular
compounds (compounds formed from covalent bonds), and polar molecules (molecule
with one side being positive and the other side being negative.) For
question #10 define hydrogen bonds. The hydrogen bonds cause the cohesion to
occur. This was seen by the water bubble that formed on the penny in your
earlier experiment." Resume the tape. Pause the tape
when the words, "The Shape of Water" appears on the screen.
Audio is music. Say, "What is a hydrogen bond? (strong attractive
forces) This next segment of the video is a review of water's polar
nature." Resume the tape. Pause the tape when there is
a head shot of Dana. She says, "So all the special characteristics of
water relates to the shape and the polar nature of this molecule." Fast
forward the tape to where the text appears and the audio is, "Sixty
seconds of Science." Say, " In question #11 explain why water
expands when it freezes. This last segment reviews, water's molecular
structure, polarity, and the reason why ice expands." Stop the
tape when the graphic of the solid water molecules appear. Audio is,
"The attractive forces of water, the hydrogen bonds, gives water its
extraordinary characteristics." Say, "Why does water expand as
it freezes?" (The polar nature of every water molecule takes over and
like charges repel creating spaces that other water molecules cannot enter
because of the electrical repletion.)
FOCUS FOR VIEWING
To give the students a specific responsibility while viewing,
say, "You will be watching a video that brings into focus the unique
properties of water such as, density anomaly, high boiling and freezing point
and, high specific heat capacity. If you have ever wondered why ice
floats, this is your chance to find out.
VIEWING ACTIVITIES
Say, "Listen and record the three phases of water for
question #12. Record important uses of water in question #13." Begin
Water's Physical Properties video where Darren is walking on the snow.
Darren says, "If water behaved like most normal substances, ice would sink
to the bottom and then more ice would form on top". Pause the
tape when Bryce is lying on the ice as he says "How does water absorb so
much of the sun's energy?" Say, "What are the three states or phases
of water? (ice / solid, water / liquid, vapor / gas) Name some uses of
water." (cooking, cleaning, bathing, universal solvent, transportation,
major component in plants and animals, found in the air)
Fast forward to where the words "What's so special
about water?" appear in white letters against a green and blue blotched
background. Music is playing in the background. Say, "Listen
and record in #14 the three out of the four special properties of water. Resume
the tape. Pause the tape when the phrase "High specific heat
capacity" is superimposed on the images of fireman. Audio is,
"Water has a high specific heat capacity". Say, "What were
the three special properties of water mentioned in the video?" (high
surface tension, high boiling and freezing points and, high specific heat
capacity.)
Fast forward the tape where Brendon and Tanya are at the
table. Tanya is holding up a glass of water as Brendon drops ice into her glass.
Audio is "Here's another thing that makes water special." Say,
"Listen for the
definition for density anomaly and an example. Record in
question #15 the definition of an anomaly. In #16 draw convection
currents." Resume the tape. Pause the video at
the convection graphic for students to make their drawings. The
audio is, "As cool water sinks, it forces warmer water to rise to the
surface where it is cooled by the air." Say, "What is density
anomaly and give an example?" (An example is ice. It floats instead
of sinks as in most normal substances. Ice is less dense than its liquid
state.) What is an anomaly? (something that is abnormal, an
exception to the rule.) Use dry erase markers on the screen to further
communicate the circular motion of convection currents. Wipe the screen.
Say, "When does water freeze? Record your answer on question #17.
Record your answer on question #14 for the fourth physical trait of water."
Resume the tape. Pause the tape where Darren is sitting on
an ice chest and Bryce is looking into the hole in the ice. Say, "When does
water freeze in a lake or pond? (When the water cannot sink anymore, it cools to
zero degrees Celsius and freezes.) What is the fourth physical
trait mentioned?" (density anomaly) The following demonstration must
be set up three hours or one day before students observe the bottles from the
freezer. Place isopropyl alcohol in bottle A. Fill bottles B and C
with tap water. Place three tablespoons of salt into the water of bottle
C. Note all bottles' liquid must not rise above the two inches mark below
the cap. Place all three bottles of water into the freezer for at least
three hours. Say, "I am going to pass around three bottles that have
been in the freezer for several hours. Each bottle was filled with liquid
two inches below the cap. See if you can identify which bottle contains
water, alcohol, or salt water." Have students discuss their
hypothesis for which liquid is in each bottle. Through questioning
techniques, lead students through this problem solving activity. (The
alcohol in bottle A and the salt water in bottle C will not freeze in a regular
freezer.) Say, "How can we test to see what substance is in bottle A
and C? What test could we conduct if we could not smell or taste the
substance? We know that ice floats in freshwater but, what will it do in
saltwater or alcohol? Let's find out." Each group will
pour 75 ml of bottle A and C into separate 100 ml beakers. Students will
drop an ice cube into each beaker and observe what happens. (Water expands
as it freezes. Water molecules stick together and form hexagonal
structures when the temperature lowers. This structure provides more space
between the molecules than water has at room temperature, thus the ice expands.
On the other hand, salt and alcohol have a lower freezing temperature than a
freezer can provide. The salt gets in the way of the water molecules
linking together, thus a lower temperature is needed before salt water can
freeze. Ice will float in salt water and sink in alcohol. Alcohol is
less dense than ice and thus ice sinks to the bottom.)
Fast forward the tape to when the words "Observing
Phase Change" cross the screen in a diagonal pattern. Audio is music.
Say, "Listen to the two variables mentioned in the experiment and to the
type of experiment being conducted." Resume the tape. Pause
the tape when Brendon is reading the thermometer extending out of the clear pot
of ice. He says, "The temperature is minus fifteen degrees
Celsius." Ask students, "What type of experiment is being
conducted?" (phase change)
Fast forward the tape when the steam is raising off
the pot. Audio is "The steam is beginning to raise" Say,
"For question # 18, listen and look for when a phase change occurs." Resume
the tape. Pause the tape when Darren and Bryce are standing near
the camper's pot. Audio is "The ice is less dense."
Say, "When does a phase change occur? (when a substance changes from
one state to another) In the experiment conducted by Brendon and Tanya
there were leveling off areas. Listen for the reason that there is
leveling off areas and record your answer on #19. Resume the tape.
Pause the tape when the words "Specific Heat Capacity" are
displayed. Say, "Why are there leveling off areas? (phase
changes) Fill in the blank for #20 from the sentence on the screen, the
definition for specific heat capacity. The amount of heat needed to raise
the temperature of one unit mass of substance by one degree Celsius."
Go on to explain, "This is why the sea doesn't get hot and why water has
such a moderating effect on the climate. While the tape is fast forwarding
let's discuss the snow experiment. For question #21 fill in the time interval
for the length of time to melt the ice (5 min.), for steam to form (6.5 min.),
for the water to boil (2.5 min.), and the length of time it takes to kill
microbes in boiling water (1 min.). Which experiment is more
accurate and why? (Brendon's and Tanya's experiment was more accurate because
the temperature was recorded at set intervals.)
Fast forward to the text "One change at a
time." Audio is music. Say, "Listen for the reason why
there isn't any temperature change when a phase change occurs and record your
answer on #22." Resume the tape. Stop the tape when a
graph of temperature versus time appears. Audio is "Changes in state
but not in temperature." Say, "Why do we have these periods of
no change in temperature during the phase changes?" (Energy is needed
to change the state of the substance.)
POST VIEWING ACTIVITY
Say, "In the videos we saw water's molecular structure, its
high boiling and freezing points, its high specific heat capacity, and its
density anomaly. We learned that water is a polar molecule and this is why
it was a strong attractive force. We observed the cohesive force of
water on the penny. Waters high surface tension is the reason why some
objects can float or why some insects can walk on water. Let's conduct an
experiment on surface tension. Take your clear plastic box partially
filled with water and try to float the two different sizes of paper clips.
Observe and record your results. Take your flat piece of foil and place it
on the water's surface. Add large paper clips on top of the foil until
water begins to seep in. Record your results. What was the class average?
How does this experiment relate to surface tension?"
Say, "In the Internet activity you will find that water has
more unique characteristics than those mentioned in the video. One of the
web sites has a water quiz for you to take."
ACTION PLAN
1. Have students create their own Internet water scavenger hunt.
2. Visit an electrical power plant to see how they use water's
high specific heat capacity to cool the plant.
EXTENSIONS
Language Arts
Create original riddles or songs about the unique properties of
water.
Describe the phase changes in the water molecules' point of view
Mathematics
Explore positive and negative numbers to emphasize charges that
valence electrons and ions have. Explore the molecular structure and 3-D
modeling of molecules.
Art
Create a hexagonal lattice structure using the water molecule
model as the building blocks.
Social Studies
Research the history of water as a means of transportation.
Reading
Read a novel about the Titanic. (The icebergsare examples
of water's density anomaly.)
PROPERTIES OF WATER WORKSHEET
Pre-Viewing Activity
Trial # Number of drops Draw a side view of
your penny with the water
1.________________________
2.________________________
3.________________________
AVG ______________________
Describe the water on the penny. (How is the water's
behavior on the penny?)
_____________________________________________
_____________________________________________
Viewing Activities
1. Record the volume of the gases off the Hoffman
apparatus you have seen on the video.
Hydrogen ___________ Oxygen
___________
What is the ratio: _____________.
2. Opposite charges __________________ and like charges
____________________.
3. Why is water attracted to both positive and negative
charges? __________________
___________________________________________.
4. Atoms tend towards _______________.
5. Valence electrons - ________________________________.
6. Covalent bonds - _________________________________.
7. Molecular compounds - ____________________________.
8. Polar molecule - __________________________________.
9. Draw a water molecule
with its charges.
10. Hydrogen bonds - ________________________________.
11. Why does water expand as it freezes?__________________
_______________________________________________.
12. Name the three phases of water:
_____________, _____________, ______________.
13. List some of water's importance: ______________________
_______________________________________________.
14. List the four special properties of water: ________________
_______________________________________________
_______________________________________________.
15. What is an anomaly?
__________________________________________________
16. Draw the convection
currents shown in the
side view of the pond.
17. When does water freeze in a pond?
________________________________________.
18. A phase change occurs when a substance
___________________________________.
19. In the experiment of changing ice into vapor, the leveling
off areas relate to________.
20. Specific heat capacity is the amount of heat need
to raise the temperature of one unit
_____________________________________________.
21. Melting of the ice: _____minutes.
Steam to form: _____
minutes.
Water to boil:
_____minutes.
Kill microbes in boiling
water: _____minutes.
22. Why are there periods of no change in temperature during the
phase changes?
____________________________________________.
Post-Viewing Activity
Which paper clip floated?____________
Explain. _______________________________
What was the number of paper clips that your piece of foil could
hold?________________
What was the class average? ___________
How does this experiment relate to surface tension?
______________________________
Internet Search
1. Refer to the fundamentals of Physical Geography site
http://www.geog.ouc.bc.ca/physgeog/contents/8a.html
a. Define Hydrosphere.
_______________________________________________
b. Name the three molecular structures of water._____________
solid, ______________ liquid and ______________ gas.
c. On this web site they mention six unique physical properties
of water.
Name the two properties explained in the
videos. _______________ &_____________
Name the other four properties mentioned in
this site._______
________________________________________________
________________________________________________
2. Refer to the USGS site on water http://wwga.usgs.gov/edu/mwater.html
a. Take the True-False Quiz. Name two new things that you
learned from this site.
_____________________________________________
_____________________________________________
3. Refer to the Mathmol site. http://cwis.nyu.edu/pages/mathmol/modules/water/water_teacher.html
a. Clip on the phrase: Learn about Water and Ice
Which bonds are stronger, Hydrogen or
covalent?__________
b. What shape does crystalline ice have?
________________________________________________
c. Replace the info_water.html from your current web address and
replace it with density_exp.html Why does an ice cube float in water and
not sink?
________________________________________________
d. At what temperature will the water freeze?
________________________________________________
e. There are three on-line activities for students. For
extra credit try these activities. Record your data and answer the
conclusion questions.
Updated: April 01, 2008
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