Chemistry for Everyone edited by
Applications and Analogies
Ron DeLorenzo Middle Georgia College Cochran, GA 31014
Students as Solids, Liquids, and Gases Ponnadurai Ramasami 126 Royal Road, Le Hochet, Terre Rouge, Mauritius;
[email protected] Analogies have always been helpful in conveying and clarifying concepts. The concept of solids, liquids, and gases is not clear to most students and the effect of intermolecular forces is digested with difficulty by beginners. This analogy will consider students as the particles of matter and then relate the similarities between them and solids, liquids, and gases. When the students are sitting in the classroom and the teacher is also present, the students are in a certain order. This is how crystalline particles are arranged; that is, there is a certain order and hence a definite shape. Intermolecular forces can be understood in terms of friendships and closeness among the students. Generally, more friendships will exist among students if they sit closer to each other in the class. Similarly, more intermolecular forces will exist if particles are closer to each other, as in the case of solids. Also, students in class have limited localized motion because they can turn at the waist or can move slightly, but movement from one place to another is generally not allowed during the class. Hence, like the particles of a solid, students have vibrational and rotational energies but do not have translational energy. If some
students are absent, their seats will be vacant and these may be introduced as defects in solids. If the students are sitting and they are forced closer to each other, they will try to keep a minimum distance between themselves or return to their place owing to uneasiness; hence solids are not compressible. During lunch time the students may spread around at school. Good friends keep close together but are able to move around each other as they wish; hence students can vibrate, rotate, and translate, and their behavior is like the behavior of the particles of liquids. The bell calling the students to class is analogous to the removal of thermal (kinetic) energy and initiates a liquid-to-solid phase change. After school hours when every student is at home, or at least away from school, the students behave as particles of a gas. They are free to move independently of each other and they have rotational, vibrational, and translational energies. Acknowledgments I am grateful to anonymous referees for constructive comments.
JChemEd.chem.wisc.edu • Vol. 77 No. 4 April 2000 • Journal of Chemical Education
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