Final answer:
A fresh egg will have a prominent, high-standing yolk and a substantial, thick white. As eggs age, the yolk and white deteriorate, leading to a flatter yolk and thinner white.
Step-by-step explanation:
If, when an egg is broken, its yolk stands high, and it has a thick white, then you know it is fresh. This is because a fresh egg will have a yolk that is compact and raised above the white, and the white itself will be thick and stay close to the yolk. As eggs age, the whites become thinner and the yolk can flatten and spread out as the proteins weaken and the structures within the egg break down. In terms of embryology, total cleavage occurs in eggs with less yolk, leading to an even distribution of cells, while partial cleavage takes place in yolky eggs, where the cells grow over the surface of the yolk. When discussing the properties of egg whites, or albumin, we recognize that the structure of the proteins within are held by hydrogen bonds, and when the egg is boiled, these bonds are broken allowing the proteins to aggregate into a solid mass – a process which is spontaneous and irreversible above a certain temperature.