The function of mordant in the gram staining is to expose grams positive cell to the decolorizer which dissolves the lipids in the cell wall thus allowing the crystals violent-iodine to leach out of the cell. This facilitate the cell subsequently be stained by with safranin.
Well you have to mix chemicals which caused a chemical reaction. When you mix salt and ice the freezing point of liquid changes. the ice gets colder
Methyl orange shows red color in acidic medium and yellow color in basic medium. Because it changes color at the pKa of a mid strength acid, it is usually used in titration for acids. Unlike a universal indicator, methyl orange does not have a full spectrum of color change, but it has a sharp end point.
