Building Molecules from Atoms
Grade Level		Prospective and Practicing K-8 Teachers; may be adapted for use in elementary classes.
Time		Exercises 1-3 take approximately thirty minutes. Click below to download the SemNet "1.2,3h Atoms Net", which is a completed network showing how we have put together the ideas in Lesson 2, Elements and Atoms, and Lesson 3, Molecules. This net is not used in the knowledge mapping exercises, below, but has neen provided as a guide and illustration of the ideas in these lessons. 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.
Objectives			Once you have completed these exercises you should be able to:
		1.	Given the name of a relation in one direction, generate an appropriate name for the reverse relation ray (name in other direction).
		2.	Choose appropriate relation names for linking two ideas together.
		3.	Define categories of biological molecules. The knowledge mapping exercise is intended to help the student organize his/her biology knowledge in useful and productive ways. In this exercise we focus on use of relations. Naming and describing relations is the single most difficult task in knowledge mapping, and one where the students will need the most help.
Background Information		Describing Relationships
		1.	A key to understanding is to be able to explicitly name and describe relationships between ideas. Very often we will have a fuzzy idea (an association), such as being aware that the concepts, atom and molecule, are related.
		2.	Associations are often formed because we readily cluster or associate ideas that we encounter at the same time or in similar contexts. But what is the precise nature of the relation(s) between atom and molecule?
Powerful Idea		3.	Being able to specify and describe the specific relation(s) is the key step in learning for understanding, and being able to distinguish the more salient (important, relevant) links from the less relevant ones is also valuable. In this exercise we will practice using the three relations commonly used in biology.
		4.	As noted previously, all relations are bi-directional. Thus, if molecule is related to atom, then atom must also be related to molecule.
		5.	Three relations to be explored in this exercise are shown in Table 1. Table 1. Three Common Relations Used in Biology Representations Relation Definition has part [is] part of describes a physical part of a larger object, as in molecule has part atom includes type [is] type of describes an example, an entity that is included in the larger class, category or set, as in molecule includes type protein has characteristic [is] characteristic of describes an attribute of feature of a thing, as in molecule has characteristic motion
Powerful Idea		6.	Two basic rules we use for designating the reverse ray of a relation in knowledge mapping are (a) to use the same main word (for example, part, type, characteristic), in both directions and (b) to be certain that the meanings of the two relation rays are precisely equal and opposite. For example, it would not be appropriate to say has part / is contained in because there are different nuances of meaning of the two relation rays.
		7.	The verb to be (for example, is, are) is generally omitted and thus is indicated in brackets above. The reasons for doing this are (a) brevity and (b) to avoid conflicts of plurality, as in the two possible versions of this relation, is part of and are parts of. The simple phrase, part of, works with both singular and plural concepts.
Exercise 1		Naming Reverse Relation Rays In our experience, students (and often experts as well) confuse whole / part and has type / type of (or category / member) relations in about 20% of the instances they create. In exercise 1 students are asked to name reverse relation rays and then to think about and discriminate between the whole / part and type / category links as well as other relations.
		1.	An instance is a 'concept - relation - concept' unit which can be described in each of two directions (for example, 'tree has part leaf', and 'leaf [is] part of tree').
To Do		2.	Name each of the eleven reverse relation rays in the instances in Table 2. Naming the reverse relation ray can be challenging. Chances are that not everyone will do it in the same way. However, it is important to follow the rules stated above, to (a) use the same main word in both directions and (b) be certain that the meanings of the two relation rays are precisely equal and opposite.
		3.	Instances 9 and 10 illustrate one of the finer points of these rules: Both instances describe the same event, but they use two different verbs to do it. In creating the reverse relation rays, we want to use the same main verbs as in the forward relation rays. Table 2. Fill in Reverse Relation Rays No. First Concept Relation Ray Related concept 1. molecule covalent bond has part part of covalent bond molecule 2. molecule sugar includes type type of sugar molecule 3. water polar has characteristic characteristic of polar water 4. ice solid has states state of solid ice 5. atomic nucleus protons contains contained in protons atomic nucleus 6. atom single covalent bond freely rotates around allows free rotation of single covalent bond atom 7. ball & stick atom & bond models modeled with atom & bond ball & stick 8. glucose sugar C6H12O6 has formula formula of C6H12O6 glucose sugar 9. water H+ ion & OH- ion separates to form formed by separation of atoms in H+ ion & OH- ion water 10. H+ ion & OH- ion water combine to form formed by combination of water H+ ion & OH- ion 11. glucose ring glucose straight chain rearranges to form rearranges to form glucose straight chain glucose ring There is more than one 'right' answer in some cases. You will have to use your judgment. Note that (9) and (10) describe two different instances with the same meaning but described by different words, and note how, in both cases, fidelity to the words in the first relation ray is maintained in the second relation ray. Instance 11 does not require an asymmetric relation - the same words work equally well in both directions, and thus we have produced a symmetric relation.
Exercise 2		Using Relation Rays Table 3. Relation Rays First Relation Ray Reverse Relation Ray has characteristic characteristic of models modeled by has part part of has type type of
To Do		1.	Eight relation rays are listed in Table 3 above, and 17 idea pairs are shown in Table 4 below. Choose a relation ray from Table 3 that is salient and appropriate for linking each idea pair together in Table 4. Each relation ray may be used more than once.
		Table 4. Fill in the Best Relation Ray to Connect Each Concept Pair No. First Concept Relation Ray Related Concept 1. single covalent bonds part of                water 2. atom has type oxygen 3. black ball models carbon atom 4. C6H12O6 type of organic molecule 5. high electronegativity characteristic of oxygen 6. H2 has characteristic gaseous 7. hydrogen atom modeled by white ball 8. inorganic molecule has characteristic not carbon based 9. molecule has part atoms 10. nitrogen type of atom 11. organic molecule has part carbon 12. organic molecule has characteristic carbon backbone 13. polar characteristic of water molecule 14. pure water has part water molecules 15. steel has characteristic hard 16. substance has part atoms 17. wood type of substance As in the previous exercise, there may be more than one correct answer even with this constrained set. For example, instance # 12 is probably equally correct with 'organic molecule has characteristic carbon backbone' or 'organic molecule has part carbon backbone'. Careful judgment is required in reviewing students' responses.
Exercise 3		Categories of Biological Molecules
To Do		1.	You are familiar with three of the four major groups of organic molecules because the corresponding food groups have the same names. What are they? Complete the names in Table 5.
		Table 5. Name Three Major Classes of Biological Molecules (three major food groups) Class of Molecules Hint Carbohydrates good for munching Lipids avoid too much Proteins makes body strong
		2.	The fourth group of biological molecules contains what is probably the most famous molecule of all, DNA. Do you know what this group is called? Complete the name in Table 6.
		Table 6. Name the Fourth Class of Biological Molecules Class of Molecules Hint Nucleic acid contains DNA & RNA
		3.	There are literally thousands of different kinds of biological molecules, yet they all fit into these four major groups. Molecules within each group have many properties in common.
Powerful Idea		4.	This is the power of categories and classifications in biological thinking. Instead of learning about several thousand individual molecules, we can learn the characteristics of just four major categories of molecules, and learn how to assign any given molecule to a given category. A common error made by poorer students is to use categories inconsistently and sporadically. For example, in describing a cell they may identify the nucleus and Golgi body as organelles but fail to include the mitochondria and other appropriate structures in that category. This significantly weakens their ability to learn and retrieve information. Elementary school is an ideal place to build the skills of using categories and hierarchies.