Effects of ageing on eggs

For all these experiments, use eggs which are very fresh and repeat with eggs that are fairly fresh (1-2 weeks), at least one month old and if possible, even older.

Method

1. Fill a large container with 10% salt solution and add the eggs to it.  Note whether the eggs touch the bottom, float near the bottom, half way up the container, near the surface or actually break the surface of the solution.  How can you account for these differences?
2. Carefully break the eggs out onto clean flat plates and compare the shape and height of the yolks, the proportion of the thick and thin white, and the area taken up by the eggs as a whole. What causes these changes?
3. Look into the empty shells and compare the sizes of the air spaces.
4. Measure the pH of the whites and yolks of the different eggs using pH paper.  What must have happened to cause the changes?
5. Boil the eggs for about 10 mins, cool and shell carefully.  Slice in half lengthways and notice the position of the yolk, whether it has broken through the white, any colour change and also the size of the air space.
6. Whip up raw egg whites and compare the ease of whipping, the foam stiffness and stability.