It turns out that with the heating of the stove, the water and jiaozi in the pot are heating up slowly. We know that hot objects will expand. Jiaozi and water are no exception. However, the degree of thermal expansion of objects is different. Some things expand quickly, while others expand slowly. Dumpling stuffing and dumpling skin expand faster than water, and their volume is easy to increase a lot. This, you must be very clear, cooked jiaozi is really full, much bigger than raw jiaozi. However, the weight of jiaozi did not increase. After the volume increased, the weight per unit volume decreased. According to Archimedes principle, jiaozi submerged in water will lose the weight of the same volume of water, and this lost weight is the buoyancy of water to jiaozi. Since jiaozi is big, the weight lost in the water is also big, that is, the buoyancy of water to jiaozi is greater than that of raw jiaozi. Of course, it is not a problem to float a jiaozi with a smaller unit weight with greater buoyancy. Therefore, only when jiaozi is cooked, that is, the stuffing and skin of dumplings are fully expanded, can it float. Eat jiaozi float, of course, there will be no worries.
After jiaozi cooked and floated, why did it cool a little and sink again? What used to expand rapidly must also shrink rapidly. When water cools, jiaozi shrinks much more than water. After shrinkage, the weight per unit volume of jiaozi increases and the buoyancy of water decreases. After reducing buoyancy, jiaozi, which is not enough to increase the weight per unit volume, floats, and jiaozi sinks to the bottom of the pot.
Therefore, jiaozi's ups and downs are such a trivial matter, but there are so many great truths.