Due Date_________
Name_____________
Period______
WATER ACTIVITY
PURPOSE: To understand the properties of water and relate these physical attributes to its role in
living organisms.
MATERIAL PER TEAM: water, dropper, wax paper, comb or hard rubber rod and wool (or other
object for obtaining an electrostatic charge), needle, evaporating dish, beaker, test tubes, ethanol,
mineral oil, NaCl solution, 1 ml pipette, crucible, ring stand, Bunsen burner, triangle or wire gauze,
foods (e.g. potato, milk, etc.), 1.5% gelatin or 2% starch sol., beam flashlight or projector,
microscope and slides.
Station 1 (Demo): Food contains water. Vegetables contain 80 to 95% water, meats 40 to 70%
while grains and cereals only 8 to 12%. We will determine the amount of water in some foods
(potato, milk, etc.). 5 g or more will be weighed and slowly heated in a crucible until dry but not
burnt then allowed to cool. We will then weigh the residue and calculate the percent of water loss.
How does this explain the shrinkage of meat such as hamburger when broiling? Why is powdered
milk more expensive per equal weight as compared to whole milk?
Station 2 (Demo): An ice cube will be placed in a beaker with 100 ml water and a beaker of alcohol.
Describe and explain what happens.
Station 3 (Demo): 50 ml of water & 50 ml of alcohol will be poured into a graduated cylinder
together. How many ml are now in the graduated cylinder?
Station 4: Colloidal solutions are those in which the size of the dispersed substance lies between
that of a true solution and that of a coarse suspension. Because of the difference in the size of the
particles, colloidal solutions have properties different from those of true solutions.
A 1.5% gelatin solution or a 2% starch solution has been prepared for you. Both are examples of
lyophillic colloids. Whipping cream, salad dressing and facial powders are examples of common
colloids. Milk is an emulsion of butterfat in water wherein the protein, casein, acts as the stabilizing
substance to produce a colloid. Soap does the same to oil and water. Many of the proteins in the
blood are in an electrically charged, colloidal state.
Station 4A (Demo): A test for colloids is the Tyndall effect. A beam of light will be passed
through a beaker containing a sodium chloride solution and one containing the colloid of gelatin or
starch solution. What is the difference?
Station 4B: Brownian movement noted under the microscope is another colloidal property. Place a
drop of salt solution on one half of a slide and a drop of the colloid solution (gelatin or starch) on
the other half. Use cover slips and describe the movement seen through a microscope. Can you see
movement in both liquids?
Station 5: Use an eyedropper and place drops of water on a penny. Describe what happens. What
property of water is demonstrated?
Station 6: Place a drop of water on a glass slide. Put another glass slide on top of the drop of
water. Try to separate the slides. Is it easy to do? What property of water keeps the slide
together?
Station 7: Place a drop of water on a glass slide. Use a glass tube (capillary tube if available) and
put the end of the tube in a drop of water. What happens? What property of water causes the
water to move up the tube?
Station 8: Write the formula for water.
Draw the Lewis electron-dot configuration for water.
Station 9: At the sink, turn on a fine-stream of cold water. Using different objects such as a
comb, pen, glass rod or hard rubber rod, develop an electrostatic charge by rubbing the objects
with wool or cotton cloth. Place the tip of the object near the stream of water. Describe what
happens. Do water molecules have polarity (a positive and negative end)? Draw a water molecule to
show its polar behavior. Does the water bend? What property of water is demonstrated?
Station 10: Place a small drop of water on a piece of wax paper. Describe its shape. Try cutting it
in half. What happens to the drop? Place some water in a beaker and float a needle on the surface.
Describe the results. What property is demonstrated? Would it matter if you place the droplet of
water on loose-leaf paper as opposed to wax paper? Why or why not?
Station 11: Shake some pepper on top of water in a small beaker that is provided. Using a
Toothpick first touch one end of the toothpick into the water then the other end. One end
appears darker in color so that you will be able to record your results. What happens to the water
and pepper when each end is touched? Why?
Station 12: An emulsion may be defined as a metastable suspension of two or more substances
ordinarily insoluble in each other.
Place 5 ml of water and 5 ml of cottonseed oil or vegetable oil (may be stained with Sudan IV) in a
test tube. Shake vigorously. How stable is this emulsion? Which liquid forms drops?
Add a drop of liquid detergent to the emulsion and shake again. Describe your results. Bile,
produced by the liver and stored in the gall bladder yields the same results. What is the use of bile
in the body?
Milk is a common emulsion. Examine a drop of milk under the microscope and look for fat droplets.
Station 13 (Demo): Outside, we will use a 2 liter bottle of diet soda and a roll of Mentos to see
how tall of an eruption we can make. First we will open the bottle of soda, and then we will load the
Mentos into a test tube to make it easier to load them all into the bottle at the same time. Why do
we see what we see? What property of water causes the eruption?
Adapted from HENRY ROSENBAUM, INSTRUCTOR, Fasman Yeshiva High, Skokie IL and from
Lynn Mirello