Melting vs Dissolving
Melting thiab dissolving yog theoretically lub cev thiab tshuaj phenomena, tab sis lawv tshwm sim txhua hnub nyob rau hauv pem hauv ntej ntawm peb ob lub qhov muag. Koj tsis tau pom cov dej khov yaj hauv dej? Koj tsis tau pom ib khob kas fes li cas? Zoo, cov no yog melting thiab dissolving txheej txheem raws li peb ua tim khawv txhua hnub. Txawm li cas los xij, muaj ib txwm nyiam xav tias ob qho tib si txhais tau li cas vim tias, thaum kawg ib yam dab tsi tau hloov mus ua kua raws li peb saib.
Kev sib tw
Melting yog ib theem hloov. Muaj 3 theem tseem ceeb hauv qhov teeb meem tuaj yeem tshwm sim. Cov no yog khoom, kua, thiab roj. Thaum cov khoom siv los ua nws cov kua, qhov tshwm sim no hu ua "melting" lossis fusion. Txhawm rau kom cov khoom tawg, lub zog yuav tsum tau muab. Lub zog no tuaj yeem muab tau raws li qhov kub thiab txias. Qhov kub ntawm cov kua ua kua yog hu ua "melting point". Txij li thaum lub sij hawm hloov nyob rau hauv equilibrium; piv txwv li, nws tuaj yeem tshwm sim hauv ob txoj hauv kev, nws kuj yog "qhov chaw khov" rau qhov rov qab cov tshuaj tiv thaiv.
Yuav ua li cas? Thaum ib yam khoom muaj nyob ua ib qho khoom nws muaj cov qauv siv lead ua lossis cov qauv nruj heev. Piv txwv li, NaCl (ntsev) muaj nyob rau hauv lub lattice qauv qhov twg txhua Na+ yog surrounded by 6 Cl– ions thiab txhua Cl – ion yog surrounded by 6 Na+ ions. Rau cov khoom no los ua cov kua no cov qauv siv lead ua yuav tsum tawg thiab nws yuav tsum muaj lub zog ntau, qhia tau tias muaj qhov melting siab heev. Cov khoom uas tuaj yeem tawg tau yooj yim rau hauv lub xeev ua kua tsawg dua muaj cov ntsiab lus melting qis dua.
Kev sib tw
Dissolving, ntawm qhov tod tes, tsis yog ib theem hloov. Nws yog qhov yooj yim thaum cov khoom sib xyaw nrog cov kua thiab ruaj khov hauv cov kua nruab nrab. Cov khoom, uas tau yaj, yog hu ua "solute" thiab nruab nrab nws yog yaj nyob rau hauv hu ua "solvent" uas ua ke ua ib "kev daws teeb meem". Yuav ua li cas rau dissolving? Yog tias peb coj NaCl ua piv txwv dua, peb pom tias nws nyuaj heev kom yaj nws. Tab sis dissolving NaCl, hais nyob rau hauv dej, yog heev yooj yim piv. Qhov no yog vim hais tias thaum cov ions Na + thiab Cl- sib cais hauv cov kua nruab nrab cov dej molecules npog txhua qhov los ntawm kev ua "hydration spheres" nyob ib puag ncig lawv. Qhov no stabilizes lawv lub neej nyob rau hauv cov kua nruab nrab. Raws li tau hais ua ntej, kev sib cais tsis tas yuav yog cov khoom ruaj khov hauv cov kua, tab sis nws tuaj yeem yog lwm cov kua, lossis txawm tias muaj roj. Thaum haus dej haus cawv yog tov nrog lwm cov kua dej qab zib, qhov twg cov kua yog yaj nyob rau hauv lwm yam, thiab nyob rau hauv dej qab zib peb paub hais tias CO2 roj yog yaj nyob rau hauv dej.
Qhov txawv ntawm Melting thiab Dissolving yog dab tsi?
• Melting yog ib theem hloov (kua-kua) tab sis dissolving tsis.
• Yuav kom yaj cov khoom muaj zog yuav tsum tau muab los ntawm qhov kub thiab txias tab sis kom yaj nws feem ntau tsis tseem ceeb (qee yam khoom xav tau lub zog kom yaj).
• Rau cov khoom kom yaj nws yuav tsum ncav cuag qhov kub ntawm qhov "melting point" tab sis rau kev yaj tsis muaj qhov yuav tsum tau ua.
• Molten substance is the pure kua form of solid that was melted but a solution is always a mix of two or more.
