EXERCISE NO. 1 PROPERTIES OF WATER I. INTRODUCTION Water is an essential requirement for life on earth to exist, and all living organisms are partly made up of water. Because of the special properties of water, both physical and chemical, it enables to sustain and maintain biological processes from its basic function as a medium for cellular transport up to its influence in atmospheric conditions in a global scale. In its purest form, water is odorless, tasteless, and nearly colorless. As a chemical compound, a water molecule is a combination of two hydrogen atoms and an atom of oxygen via hydrogen bond. This type of bond is the reason behind many of water’s unique properties. II. OBJECTIVES At the end of the experiment, the students are expected to: 1. Determine and compare the different selected physical and chemical properties of water and other clear solutions. 2. Distinguish and identify water from the other clear solutions. 3. Explain natural phenomena using the understanding on water properties. 4. Elucidate and connect the diversity of freshwater habitats to the unique properties of water. III. MATERIALS 6 Beakers Baking soda Eye droppers 8 Graduated cylinder Paper clips Weighing scale 12 Test tubes Paper towels Coins River water Isopropyl alcohol Hydrogen peroxide Saltwater Vinegar Mineral oil Solutions: Prepared by: Rhoniel Ryan J. Ymbong Freshwater Biology Page 1 IV. PROCEDURES The following tests for water properties should be administered to all samples of clear solutions namely: tap water, saltwater, alcohol, vinegar, mineral oil, and hydrogen peroxide. Record all the observations and results on the data table provided. Test 1. Cohesion 1. Place a coin on a flat surface. 2. Using a dropper, drop the liquid sample on top of the coin and observe the appearance of the liquid as it collects on the surface of the coin. 3. Record the number of drops that can be placed on the coin before the water runs off. Questions: 1. What is cohesion? 2. Why do water molecules tend to stick with one another? Test 2. Adhesion 1. Cut the paper towels into long strip. 2. Dip about 1cm of one end of the strip to the liquid for 1 minute. 3. Remove the strip from the liquid and measure the number of centimeters the liquid had travelled up the paper strip. 4. Record the measurement in the data chart. Questions: 1. What is adhesion? 2. How can this property explain the movement of water to travel against gravity up the paper towel? Test 3. Surface tension 1. Place the liquid sample in a beaker. 2. Carefully place the paperclips one at a time on top of the liquid sample and let it float. Make sure the paperclips are dry before administering the test. 3. Continue to place paperclips on the liquid surface until one of the clips sinks. 4. Record the results. Prepared by: Rhoniel Ryan J. Ymbong Freshwater Biology Page 2 Questions: 1. What is surface tension? 2. Why do paper clips don’t float with the other liquids? Test 4. Solubility A 1. Pour a small amount of liquid into a test tube. 2. Add a pinch of salt into the test tube. 3. Stir for one minute. 4. Observe what will happen. 5. Record the result. B 1. Pour a small amount of liquid into a test tube. 2. Add two drops of oil. 3. Stir for one minute and observe. 4. Record the result. Questions: 1. Does the salt dissolve in water? Why? 2. Does the oil dissolve in water? Why? Test 5. pH 1. Obtain a strip of a litmus paper and stick one end into the liquid. 2. Remove the strip and air dry for 30 seconds. 3. Determine the pH using the color chart provided. 4. Record the result. Questions: 1. What is the normal pH of water? 2. How does pH affects life in water? Prepared by: Rhoniel Ryan J. Ymbong Freshwater Biology Page 3 Test 6. Chemical Reaction 1. Pour a small amount of the liquid into a test tube. 2. Add 1 gram of baking soda to the test tube and stir 3. Record your observations. Questions: 1. What is the product when water and baking soda were mixed? 2. How does water trigger chemical reactions? Test 7. Density 1. Using a balance, get the mass of the 10mL liquid sample by subtracting the mass of the empty cylinder from the mass of the cylinder with liquid. 2. Calculate for density. Question: 1. What is density? 2. How does density affects the distribution of water in the natural settings? Table 1. Observations and results on the physical and chemical properties across sample. Tests Tap water Saltwater Isopropyl alcohol Vinegar Mineral Oil Hydrogen peroxide 1. Cohesion 2. Adhesion 3. Surface tension 4. Solubility 1 5. Solubility 2 6. pH 7. Chemical reaction 8. Density V. GUIDE QUESTION 1. For each water property, give and explain a concrete example of natural phenomena happening in a freshwater habitat that is governed by a water property. 2. How important is water in the sustenance and maintenance of aquatic ecosystems? Prepared by: Rhoniel Ryan J. Ymbong Freshwater Biology Page 4 VI. REFERENCES Dodds, W. K. (2010). Freshwater ecology: concepts and environmental applications. 2nd edition. Academic press. Dodson SI. 2005. Introduction to Limnology. New York: McGraw Hill. Kalff, J. (2002). Limnology: inland water ecosystems (Vol. 592). New Jersey: Prentice Hall. Jaranilla B et al. 2007. The Science of Life. Mutya Publishing House Inc.: Valenzuela City. Solomon E et al. 2008. Biology. China Translation and Printing Services. LTD, Philippines. Prepared by: Rhoniel Ryan J. Ymbong Freshwater Biology Page 5