. ▁▁ ▁Cong ru ent ▁mel ting ▁point ▁represents ▁a ▁definite ▁temperature ▁just ▁like ▁the ▁mel ting ▁points ▁of ▁pure ▁components . ▁In ▁the ▁phase ▁diagram , ▁the ▁con gru ent ▁mel ting ▁point ▁D ▁of ▁comp ound ▁AB ▁lies ▁above ▁the ▁mel ting ▁points ▁of ▁pure ▁components ▁A ▁and ▁B . ▁But ▁it ▁is ▁not ▁necessarily ▁true . ▁There ▁are ▁different ▁types ▁of ▁systems ▁known ▁in ▁which ▁the ▁ ▁con gru ent ▁mel ting ▁point ▁is ▁observed ▁to ▁be ▁less ▁than ▁mel ting ▁points ▁of ▁pure ▁components . ▁This ▁happens ▁for ▁inter - met all ic ▁comp ounds . ▁For ▁example , ▁M g Si 2 ▁ ▁See ▁also ▁Cong ru ent ▁transition ▁In con gru ent ▁mel ting ▁Ph ase ▁diagram ▁Ph ase ▁rule ▁ ▁References ▁ ▁Category : Ph ase ▁trans itions ▁Category : Material s ▁science <0x0A> </s> ▁A ▁conserv ative ▁replacement ▁( also ▁called ▁a ▁conserv ative ▁mut ation ▁or ▁a ▁conserv ative ▁substitution ) ▁is ▁an ▁am ino ▁acid ▁replacement ▁in ▁a ▁protein ▁that ▁changes ▁a ▁given ▁am ino ▁acid ▁to ▁a ▁different ▁am ino ▁acid ▁with ▁similar ▁bio chem ical ▁properties ▁( e . g . ▁charge , ▁hydro ph ob icity ▁and ▁size ). ▁ ▁Con vers ely , ▁a ▁radical ▁replacement , ▁or ▁radical ▁substitution , ▁is ▁an ▁am ino ▁acid ▁replacement ▁that ▁ex changes ▁an ▁initial ▁am ino ▁acid ▁by ▁a ▁final ▁am ino ▁acid ▁with ▁different ▁phys ico chem ical ▁properties . ▁ ▁Description ▁▁ ▁There ▁are ▁ 2 0 ▁naturally ▁occurr