1-3 物態（下）

In the last part of chapter 3, we will once again jump into the microscopic world to find the origin of latent heat, and the principle behind evaporatoin. At the heart of these topics is an important concept called "potential energy", which is related to the attractive force between particles. 0:00 Opening 0:40 States of matter from microscopic view 3:00 Kinetic energy and potential energy 4:52 Microscopic explanation of latent heat 7:41 Microscopic explanation of evaporation Show all topics https://bit.ly/physics_concepts_eng ------------------------------ Supplementary information: [Electrostatic force and chemical bond] In the video, I said "particles are attracted together by electrostatic force". Actually, this is kind of an oversimplified way to put it. If you are taking chemistry, you should have learned about different kinds of chemical bonds, such as ionic bond, covalent bond, hydrogen bond, Van der Waals force, etc. Atoms and molecules are held together by these chemical bonds. So what is the relationship between electrostatic force and chemical bond? By its nature, chemical bond IS electrostatic force. However, one chemical bond is the overall result of many pairs of electrostatic forces. Take water as an example. A "particle of water" is a water molecule, which is composed of 2 hydrogen atoms and 1 oxygen atom. A hydrogen atom is composed of 1 nucleus and 1 electron, while an oxygen atom is composed of 1 nucleus and 8 electrons. Thus, a "particle of water" is actually "3 nuclei and 10 electrons". Assuming that an atomic nucleus is a simple charged particle, the "interaction between two particles of water" is the "interaction between 26 simple charged particles", which involves 26C2 = 325 pairs of electrostatic forces. These 325 pairs of forces can be broken down and (approximately) re-grouped into "forces within 6 atoms", 4 covalent bonds, 1 hydrogen bond and 1 Van der Waals force: Electrons and nuclei are attracted together by electrostatic force to form 6 atoms, hydrogen atoms and oxygen atoms are attracted together by covalent bonds to form 2 water molecules, the water molecules are attracted together by a hydrogen bond and a Van der Waals force. In chemistry lessons, your teacher clearly distinguish between molecules, atoms, and various kinds of chemical bonds. In physics lessons at high school level, we just loosely say "particles" and "electrostatic force". (By the way, when I made the animation in this video, I did not simulate the particles according to rigorous mathemical models of chemical bonds. Instead, I used a spring model and a particle collision model, which are relatively simple.) ------------------------------ Acknowledgements: 1：22 video by Amazing Magnetic (   • Video  ) 1：31 image by XRDoDRX [modified] (https://commons.wikimedia.org/wiki/Fi...) 1：32 image by Visitor7 (https://commons.wikimedia.org/wiki/Fi...) 1：41 image by Danski14 (https://commons.wikimedia.org/wiki/Fi...) 3：54 image by Tebo Steele (https://www.flickr.com/photos/1816289...) Royalty Free Music from https://audiohub.com #DSE #physics #thermodynamics #物理 #熱和氣體 #熱力學