The Properties of Water
Grade Level		Prospective and Practicing K-8 Teachers; may be adapted for use in elementary classes
Time		Exercises 1-4 take approximately 30 minutes.
Objectives			Once you have completed this knowledge mapping exercise, you should be able to:
		1.	Organize ideas into categories of similar types.
		2.	Classify ideas into hierarchies of larger and smaller ideas.
		3.	Develop a better understanding of some key relationships used in biology. Click below to download the SemNet "1.1 Water Net", which is a completed network showing how we have put together the ideas in the Water Lesson This net is not used in the knowledge mapping exercises, below, but has been provided as a guide and illustration of the ideas in this lesson. This net provides a useful exemplar and guide, but it should not be considered THE right answer. It is important to understand that we all think in different ways.
Background Information			Circle diagrams provide one way of graphically organizing ideas to illustrate their inclusivity. Completing the exercises below will test your knowledge about important molecules of life, including water and oils. These exercises aim to help students distinguish between more general and more specific classes of ideas, and to distinguish between different kinds of ideas.
Exercise 1		Organizing Inclusive Ideas
To Do		Insert the terms below into the appropriate circle in Figure 1, below. A term may be used more than once. adhesion cohesion hydrogen bonding capillary action density surface tension
		Figure 1. Some Characteristics of Water Adhesion, capillary action, cohesion, hydrogen bonding, and surface tension are all effects produced by the polar nature of the water molecule. The polarity results in hydrogen bonding which in turn produces adhesion (H-bonding between molecules of different types); capillary action (H-bonding between water and a polar structure); cohesion (H-bonding between molecules of the same type); and surface tension (H-bonding producing cohesion which in turn produces the surface characteristics). Density, on the other hand, is a function largely of the molecular weight of water. As we shall see in subsequent labs, density is also affected by hydrogen bonding, resulting in the unusual state in which solid water is less dense than liquid water. For this reason, knowledgeable students may place density in both circles.
Exercise 2		Classifying Ideas
To Do		Place each of the following ideas in the appropriate circle in Figure 2, below. Each idea may be used more than once. adhesive dissolving mixing boiling gaseous separated cohesive liquid separating dissolved mixed solid
		Figure 2. Distinguishing Among Characteristics, States and Processes There are three states of matter: solid, liquid and gas. Two were included in the list above. Matter (such as water) retains the same molecular structure in all three states (water is H2O in all three states). Processes are events that change over time. In boiling, water turns from liquid to gaseous state; in dissolving, the molecules of a solid or gas disperse into a solvent such as water; in mixing, two substances are intermixed, as when water and oil are shaken together; in separating, mixed substances such as water and oil spontaneously separate into different layers as a result (in this example) of the polarity of water and non-polarity of oil. Characteristics describe a thing, a state, a condition, an event, or other idea. They are typically described by adjectives or adverbs.
Exercise 3		Categories Figure 3, below, illustrates that water is a category of things that includes salt water, fresh water, distilled water, and colored water, among others. Colored water contains both water and dye, so might be shown as overlapping with both concepts.
		Figure 3. Many Kinds of Water
To Do			Organize each of the following ideas into one of the six circles in Figure 4, below. An idea may be used more than once. water oil detergent polar substance non-polar substance amphipathic molecule
		Figure 4. Bigger and Smaller Ideas The generic idea is more general than the specific idea and thus goes in the larger circle. There are many different polar substances - water is one example. Likewise, detergent is one class of amphipathic molecules and oil is one type of non-polar substance.
Exercise 4		Water/Oil Interfaces in Cells Water is the stuff of life. Many different kinds of molecules dissolve in water. Many reactions occur in water solutions.
Powerful Idea		The water - oil interface provides the basis for spontaneous cell formation. Because oils avoid mixing with water, amphipathic phospholipid molecules spontaneously form a phospholipid bilayer such that the outer surfaces consist of polar heads (interacting with the watery environment inside and outside the cell) and the center of the bilayer consists of non-polar fatty acids (Figure 5).
		Figure 5. Phospholipid Bilayer in cell membranes The phospholipid bilayer forms a membrane around the cell. If phospholipids and water are mixed and shaken, micelles (empty cells) will spontaneously form. Molecules in the body seek one of these layers.
To Do		Put the molecules below into the environment (Figure 6) where each is most likely to be found. Figure 6. Molecules and Their Likely Environments
		polar amino acid molecule from eating hamburger a fatty acid from the same hamburger vitamin E (a non-polar molecule) from the veggies vitamin A (a polar molecule) from the veggies testosterone (a non-polar steroid hormone) from the testes insulin (a polar protein hormone) from the pancreas an amphipathic transport protein The simple rule here is that polar molecules will seek a polar environment, non-polar molecules will seek a non-polar environment, and amphipathic molecules are likely to go into a membrane where each part of the molecule can find a compatible environment.