学科理解:比较分子晶体熔点应综合考虑熔化焓变和熔化熵变  

Subject Understanding: Analyzing Melting Points of Molecular Crystals Should Consider Both Enthalpy Change and Entropy Change of Melting

作　　者：翁雪香 周奇昕 吴朝辉 WENG Xue-Xiang;ZHOU Qi-Xin;WU Chao-Hui(College of Chemistry and Materials Science,Zhejiang Normal University,Jinhua 321004,China;Dongyang Middle School,Dongyang 322100,China)

机构地区：[1]浙江师范大学化学与材料科学学院,浙江金华321004 [2]东阳中学,浙江东阳322100

出　　处：《化学教育（中英文）》2024年第23期99-103,共5页Chinese Journal of Chemical Education

基　　金：浙江省课程思政教学研究项目(202262)。

摘　　要：分子晶体熔点的解析需要从熔化过程的自发性角度出发,综合考虑晶体熔化时的熔化焓变[ΔH(熔化)]和熔化熵变[ΔS(熔化)]。其中ΔH(熔化)与分子间作用力正相关,ΔH(熔化)越大,熔点可能越高。分子间作用力主要包括氢键和范德华力。除了强极性分子外,作为范德华力主要构成的色散力受相对分子质量、分子变形性、分子间距等因素影响。同时,分子变形性又会增大分子晶体熔化时的ΔS(熔化),ΔS(熔化)越大,分子晶体的熔点越低。因此,解析分子晶体的熔点时必须关注分子的变形性。教师应该积极主动地开展针对性学习,完善自己的知识结构,增强化学学科理解,这样才能在影响熔点的众多因素中确定主要影响因素。The analysis of the melting point of molecular crystals requires a spontaneous perspective on the melting process, considering both the enthalpy change of melting(ΔH_m) and the entropy change of melting(ΔS_m). ΔH_m is directly related to intermolecular forces, where a larger ΔH_m results in a higher melting point. Intermolecular forces primarily consist of hydrogen bonds and van der Waals forces. Apart from strongly polar molecules, van der Waals forces, primarily composed of dispersion forces, are influenced by factors such as relative molecular mass, molecular deformability, and intermolecular distance. Simultaneously, molecular deformability increases the ΔS_m during the melting of molecular crystals. A larger ΔS_m leads to a lower melting point of molecular crystals. Hence, analyzing the melting point of molecular crystals necessitates attention to molecular deformability. Teachers should actively engage in targeted learning to enhance their knowledge structure and deepen their understanding of the chemistry discipline. This approach enables the identification of the primary influencing factors among the numerous elements affecting the melting point.

关 键 词：分子晶体熔点 分子变形性 熔化焓 熔化熵 

分 类 号：G633.8[文化科学—教育学]