Q1.
What change can you make to this setup to make the egg float in water instead of sinking?
Answer
Dissolve plenty of common salt in the water and stir until no more will dissolve. The egg that sank in tap water will lift off the bottom and float in the salt solution.
What to do, step by step:
- Take the egg out and keep the same tumbler of tap water.
- Add salt a spoonful at a time, stirring after each, until the solution is close to saturated.
- Lower the egg in gently. It will rise and float with a small part of it above the surface.
Why it happens: You have not changed the egg at all — you have changed the liquid. Dissolving salt adds a large amount of mass to the water, while the volume increases only slightly because the salt particles slip into the gaps between the water particles. Mass up, volume almost the same, so Density = Mass/Volume goes up. Tap water is a little less dense than a fresh egg, so the egg sinks; once enough salt is dissolved, the solution becomes denser than the egg and the egg floats.
Try this: Fill the tumbler half with strong salt solution, then pour plain water very gently down the side so that it rests on top without mixing. Lower the egg in and it will come to rest in the middle — floating on the salt solution and sunk in the plain water at the same time. This is also the reason a person floats so easily in the Dead Sea.