transformation from thermal energy to mechanical 2. Why do we choose to learn the rules which gover energy (为什么要研究热能与机械能之间的转换规律?) (1) Categories of energy resources in nature (自然能源的种类) A. Chemical energy(化学能): such as coal(煤炭) crude oil(石油) natural gas(天然气) firedamp(沼气)retc www.themegallery.com Company Logowww.themegallery.com Company Logo (1) Categories of energy resources in nature (自然能源的种类) A. Chemical energy（化学能）: such as : coal（煤炭） crude oil（石油 ） natural gas （天然气） firedamp （沼气） , etc. 2. Why do we choose to learn the rules which govern transformation from thermal energy to mechanical energy? (为什么要研究热能与机械能之间的转换规律？）