Water Fun

Introduction:

Water is a miraculous compound. There is nothing else in the world like it. Not only does it taste good after a tough hike, look good when falling from cliffs, and feel good on a hot summer's day, it also makes the miracle of life (yours and mine!) possible. In this assignment you will see water in action and, no doubt, some of its actions will seem miraculous.

Assignment:

Do the following demonstrations, either to yourself or with your family. After each demonstration answer the analysis questions. If you are unsure of the answers to the questions, refer to the previous assignment (Assignment 2.3, “Water Ya Know About That”) or to the notes at the end of this assignment.

1. Demonstration: BOAT DRIVE

· Materials: paper or transparency plastic, scissors, water, tray, eyedropper, dish detergent.

· Procedure: Cut a thick arrow out of paper or a plastic overhead sheet. Cut a circle out of the tail of the arrow. This is the "boat". Fill the tray with water and place the boat on the surface of the water in the tray. Using an eyedropper, place a single drop of detergent in the circle at the end of the arrow.. Watch what happens to the boat.

Analysis

a. What made the boat move?

b. Was the boat pulled or pushed across the surface. Explain.

c. What did the detergent do to the surface of the water?

2. Demonstration: QUICK PEPPER

· Materials: ground pepper, water, bowl, eyedropper, dish detergent, pepper corn, clear drinking glass

· Procedure: Sprinkle some ground pepper on the surface of the water in the bowl. Is the pepper truly floating or just sitting on the surface. To find out, drop the pepper corn in the glass. Next use the eyedropper to place a single drop of detergent in the center of the bowl. Observe what happens. Next, add a little more soap to the dish and watch what happens to the pepper.

Analysis:

a. Did the pepper corn float on the water? The pepper flakes?

b. What did the detergent do to the surface of the water.

c. Why did the pepper sink at the end?

3. Demonstration: PENNIES

· Materials: 2 drinking glasses, water, pennies, detergent

· Procedure: Fill each glass exactly to the brim with water. Pour a drop or two of detergent in one of the glasses. Add pennies to each glass, counting the number of pennies each glass will hold until water begins to overflow the glass. Observe what happens.

Analysis:

a. What is the shape of the surface of the water before it overflows? Describe what you see.

b. How many pennies were put in each glass?

c. Why did less pennies fit into one of the glasses?

d. What do you think the soap does to the molecules at the surface of the water?

4. Demonstration: COLORFUL CARNATION

· Materials: white carnation, red and blue food coloring, two small glasses or jars, scalpel or sharp knife

· Procedure: Cut the stem of a white carnation so that it is about 10 cm long. Carefully split the stem in half, lengthwise, cutting up towards the flower. Place one half of the stem in red food coloring and the other half of the stem in blue food coloring. Leave it over night.

Note: Use caution when cutting with the knife or scalpel.

Analysis:

a. Why did the carnation change colors?

b. Would it be possible to make a carnation turn three or four colors? How?

c. If the water is not colored, does it move up the same way? How do you know?

5. Demonstration: TOWEL CLIMB

· Materials: two identical buckets, cloth towel, water

· Procedure: Fill one bucket with water and leave the other one empty. Put the two buckets side by side on a table or on the floor. Place a towel in the wet bucket and drape one corner of the towel in the dry bucket. Leave the set up over night.

Note: This set-up will work faster if a wet towel is used.

Analysis:

a. Explain what happened.

b. Is it possible for all the water to move to the second bucket? How?

c. Will the water stop transferring itself at any point?

d. What would happen if the empty bucket were higher? Lower?

6. Demonstration: CREATIVE WATER TRANSFER

Analysis:

a. Why did the water move along the string?

b. Why is it best to use a wet string?

c. What could be used to replace the string? the water?

7. Demonstration: LAYERING

· Materials: tall, clear vase or jar, water, oil, rubbing alcohol, food coloring

· Procedure: Pour blue colored water into the jar. Carefully and slowly pour oil down the inside of the jar so that it floats on top of the water. Next carefully and slowly pour red colored alcohol down the inside of the jar so that it floats on top of the oil. Observe the layers.

Analysis:

a. Why don't the three layers mix together?

b. Why factor determines the order in which the layers sit?

c. What would happen if you put the liquids into the jar in a different order?

8. Demonstration: DIFFERENT SIZE CANDLES

· Materials: two jars, rubbing alcohol, water, two pieces of candle wax (one large and one small)

· Procedure: This is another great one for your friends, family, or siblings. Prepare two identical jars. Put water in one jar and alcohol in the other. Be sure to put an the same amount of liquid in each jar. (Do not tell your family that one beaker does not have water in it.) Prepare two pieces of candle wax: one small and one large. Put the small one in the water and the large one in the alcohol. Ask for explanations of what happens to the different pieces of wax. Next switch the pieces of wax, putting the small one in the alcohol and the large one in the water. Observe what happens.

Analysis:

a. Does the size of the candle piece make a difference?

b. What characteristic of the candle determined whether or not it would float?

c. Why did the wax float in one substance and not the other?

9. Demonstration: DISSOLVING SALT

  • Procedure: Fill one small jar about half full of water, the other about half full of oil. Put 5 grams (about 1 teaspoon) of salt in each jar.

Analysis:

a. What happens to the salt in water?

b. What happens to the salt in oil?

c. How do you explain the difference?

Send me the answers to the analysis questions for all 9 demonstrations.

GOOD LUCK AND HAVE FUN!

NOTES:

SURFACE TENSION (Demonstrations 1, 2, and 3)

  • Cohesion ?Is the tendency for molecules of the same substance to stick together.
  • Water's Invisible Skin ?Below the surface all cohesive forces are balanced ?At the surface, molecules are only attracted by other water molecules beside and below ?This causes molecules at the surface to bunch together and form a "skin" on water.
  • Soap and Surface Tension ?Soap reduces surface tension by breaking the cohesive forces of water.

CAPILLARY ATTRACTION (Demonstrations 4, 5, and 6)

· Adhesion ?Is the attraction between molecules of two different substances. ?Some forms are more obvious: tape + skin, glue + paper, but also: water + skin

· Capillary attraction ?When the adhesive forces between the glass and the water are stronger than the cohesive forces between the individual water molecules, water will be more attracted to the glass ?Water will then rise up the glass sides.

· In a smaller glass tube, there is more glass compared to the amount of water in the tube and so the water rises up the tube. –

· Capillary attraction is the rising of water up small openings ?This permits water to rise up the spaces between threads in a dish cloth and cells in a plant stem.

SOLUBILITY (Demonstration 9)

Terms –

  • Solution =mixture combined on a molecular level
  • Suspension =mixture combined at a particulate level
  • Solvent =Substance in greater quantity that takes in the other ex water
  • Solute =Substance in lesser quantity that is taken in by the other substance ex sugar
  • Solubility =how readily a substance will dissolve in a solvent
  • Water is known as the "universal solvent"
  • Polarity ?Solubility depends on polarity ?Polarity means that one end of the molecule tends to be negative while the other is positive. ?Water, one the whole, is a neutral molecule. The charges are not evenly distributed. ?Polar substances will dissolve in polar substances ?Non?polar substances will dissolve in non?polar substances –
  • They will not dissolve in the opposite ?ex of polar: water, alcohol ?ex. of non?polar: oil, benzene

DENSITY (Demonstrations 7 and 8 )

  • What is Density? ?Measurement of the amount of matter contained in a given volume.

Density = Mass = grams Volume cubic centimeter ?Because one cubic centimeter =one gram of water, the density of one gram of water is: 1 gram = 1 cm3 ?Density of water is 1g/cm3. Materials with a density smaller than 1 will float.

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