Question

The milk explodes on heating. Which test is essential to avoid this problem and describe its experimental method.

Answer 1

Milk is mostly water, but it also contains vitamins, minerals, proteins, and tiny droplets of fat suspended in solution. Fats and proteins are sensitive to changes in the surrounding solution (the milk). The secret of the bursting colors is the chemistry of that tiny drop of soap. Dish soap, because of its bipolar characteristics (nonpolar on one end and polar on the other), weakens the chemical bonds that hold the proteins and fats in solution. The soap's polar, or hydrophilic (water-loving), end dissolves in water, and its hydrophobic (water-fearing) end attaches to a fat globule in the milk. This is when the fun begins.

The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules. During all of this fat molecule gymnastics, the food coloring molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity. As the soap becomes evenly mixed with the milk, the action slows down and eventually stops.

Answer 2

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Spontaneous combustion in storage (occasionally at high ambient temperature) of clothing impregnation kits containing the three title compounds was investigated. The N-chlorourea when heated evolves chlorine to give the isocyanate and a nitrene. Chlorine and the azo-dye react violently and serve as an initiation source of heat. Zinc oxide is converted to the chloride, which catalyzes violently exothermic polymerization of the isocyanate, the main contribution to the total very high exotherm (some 2 MJ/mol), which leads to vigorous smoldering decomposition of the whole mass, with temperatures in excess of 315°C being attained. In the absence of the dye, heating a mixture of the urea and zinc oxide at 5°/min leads to ignition at 130°C.