13.3. Lesson 13.3 The Nature of Solids. Overview

Transcription

1 13.3 Lesson 13.3 The Nature of Solids Objectives Describe how the structure and properties of solids are related Identify the factors that determine the shape of a crystal. Lesson Links Ch. 13 Lab 21: Allotropic Forms of Sulfur Ch. 13 Core TR: Section 3 Review Chapter 13 Online Student Edition Ch. 13 Concepts in Action: Brick and Mortar Crystal Palaces 13.3 Lesson Overview (PowerPoint file) Study WB Chapter 13 Lesson 3 Overview/Materials Overview In this lesson you will teach students the relationships between the structure of a solid and its properties such as melting point and freezing point. You will also cover how crystal structures are determined. Classroom Materials Standard 1 Block 0.5 Crystal Structure and Unit Cells: samples of wallpaper with repeating patterns, dishwashing detergent, watch glass, overhead projector, drinking straw Standard There are no items. Chemistry & You Engage Have students read the Chemistry & You feature on p Chapter 13 Online Student Edition page 1 of 5

2 Ask What do the number of bonds and bond angles between carbons in fullerenes suggest about its structure? (Some of the carbons are connected by double bonds.) Explain that the double bonds partially explain the strength of the nanotubes. Tell students that they will discover the rest of the explanation as they proceed with the lesson. Activate Prior Knowledge Engage Assess students' knowledge of types of compounds by asking them to compare the structures of molecular and ionic compounds. (Ionic compounds are composed of ions and are usually formed from a metal and a nonmetal. Molecular compounds are composed of molecules formed from two or more nonmetallic elements.) A Model for Solids Explain Explain that this is the third state of matter students will study. Review the kinetic theory and models for liquids and gases introduced in Lessons 13.1 and Have students relate the motion of particles within a gas and liquid to those in a solid. Ask How do the motions and interactions of particles in a solid relate to the melting point of that solid? (Within a solid, the particles are constantly vibrating around a somewhat fixed position. As their kinetic energy increases, so do these vibrations until the particles are no longer in fixed positions and the solid melts.) Compare the melting of a solid with the boiling of a liquid. page 2 of 5

3 Crystal Structure and Unit Cells Explore Use two simple demonstrations to explore analogies for the crystal lattice in solids. Wallpaper patterns often consist of a small group of images that are repeated to obtain the overall effect. The group of images is like a unit cell in a crystal lattice. Show students samples of wallpaper with repeating patterns. Ask students to identify the "unit cells" in the wallpaper samples. Show students how to obtain a set of " lattice points" by choosing the same point in each unit of the repeating pattern. The collection of lattice points shows the fundamental arrangement of the units in the pattern. Ask students if they could arrange the components of each unit differently to produce a different "unit cell." You can use an aqueous solution of detergent to make a model of a crystalline solid. Place the solution in a watch glass on an overhead projector and use a straw to blow bubbles into the solution. The bubbles form a regular, repeating pattern that is analogous to the arrangement of unit cells in a crystalline solid. Materials: samples of wallpaper with repeating patterns, dishwashing detergent, watch glass, overhead projector, drinking straw Crystal Structure and Unit Cells Explain Review basic geometric concepts of threedimensional solids prior to introducing Figure (Figure 13.12_part1, Figure 13.12_part2, Figure 13.12_part3, Figure 13.12_part4, Figure 13.12_part5, Figure 13.12_part6, Figure 13.12_part7, and Figure 13.12_part8). Explain that the properties of the crystals shown in the diagram are based on their geometric construction. Have students describe how a higher degree of organization and stronger intermolecular attractions between particles distinguish solids from gases and liquids. Figure 13.12, part 1 Figure 13.12, part 2 Figure 13.12, part 3 Figure 13.12, part 4 Figure 13.12, part 5 Figure 13.12, part 6 Figure 13.12, part 7 Figure 13.12, part 8 Ask students to determine if any elements besides carbon exist in different allotropic forms. (Elemental oxygen occurs as O2 and page 3 of 5

4 O3, both of which are gases; sulfur can exist as monoclinic or orthorhombic crystals; phosphorus can exist as red or white phosphorus, which are solids at room temperature.) Have students complete the Ch. 13 Concepts in Action: Brick and Mortar Crystal Palaces on PearsonChem.com. Crystal Structure and Unit Cells Extend Explain that scientists can manipulate the crystal structure of various materials to improve certain physical properties. Note that one such method is the production of alloys such as steel, as discussed in Lesson 7.4. Another method is the production of semi-conductors, which led to the development of many important advances in electronics. Have students research the history, structure and uses of key semi-conductors in today's electronics, and report their findings to the class. Assess and Remeditate Evaluate Ask students to describe orally, or in paragraph form, the distinguishing characteristics of crystalline solids and amorphous solids. (Crystalline solids are characterized by an orderly, repeating threedimensional arrangement of atoms, ions, or molecules. All crystals have a regular shape that reflects the arrangement of particles in the solid. Amorphous solids lack a well-defined arrangement of particles.) Chapter 13 Online Student Edition Then direct students to complete the 13.3 Lesson Check. Remediate Describe how a higher degree of organization and stronger intermolecular attractions between particles distinguishes solids from gases and liquids. Have students consider how these factors are related to the ability of solids to retain their shape without a container. page 4 of 5

5 Differentiated Instruction Less Proficient Readers Have students create a concept map centered around the term solid. Their maps should highlight the relationship between solids and crystals and amorphous solids. Students should determine where unit cells, allotropes, and amorphous solids fit into their concept map. Ch. 13 Core TR: Section 3 Review Special Needs Students Explain that morphing is a special effect used in films or videos to change the shape or form of an object. Have physically impaired students go online to find an example of morphing. Have them compare their example of morphing to an amorphous solid. Allow class time for them to share their findings. Advanced Students Have students do research on the crystalline structure and formation of natural, synthetic, and simulated diamonds. Have students write a short paper comparing the three kinds of crystalline structures. Focus on ELL Comprehensible Input Briefly review what students learned about crystalline structure with respect to coordinate numbers in ionic crystals and atom arrangement in metallic crystals (see Lessons 7.2 and 7.3). Then preview Figure and 13.13, pointing out the connections to the concepts from Chapter 7. Study WB Chapter 13 Lesson 3 Ch. 13 Core TR: Section 3 Review Figure Figure My Notes Homework page 5 of 5