Just boiled eggs are taken directly by hand. Although they are hot, they are passable. After a while, the water on the eggshell dried up and it felt hotter than when it was first caught.

First, how to peel eggshells smoothly?

Because a layer of water film is attached to the newly fished eggshell, the water film evaporates and absorbs heat at first, which makes the eggshell temperature drop, so it doesn't feel very hot. After some time, the water film evaporated. The heat transferred inside the egg makes the temperature of the eggshell rise again, so it feels hotter.

Boiled eggs are soaked in cold water immediately, and are taken out and peeled after being completely cooled.

Principle: When an egg is immersed in cold water, the eggshell will contract directly when it is cold, but the temperature of the protein will not drop too much and the contraction is small. At this time, the eggshell will shrink. Secondly, due to the different properties of different substances, when the whole egg is completely cooled, the protein shrinkage rate of loose tissue is greater than that of eggshells, which leads to the separation of eggshells and makes it easier to peel eggshells.

Second, atmospheric pressure experiment

Choose a bottle slightly smaller than an egg and heat a layer of sand at the bottom of the bottle. First, light a ball of alcohol cotton and put it in the bottle. Then, block the bottle mouth with the small head of the shelled egg facing down. After the flame went out, the egg was slowly "swallowed" by the bottle into its belly.

The burning of alcohol cotton makes the gas in the bottle expand by heating, and some gas is discharged. When the egg blocks the bottle mouth and the flame goes out, the pressure of the gas in the bottle becomes lower than the atmospheric pressure outside the bottle due to the temperature drop. Under the action of atmospheric pressure, eggs with certain elasticity are pressed into the bottle.

Third, the liquid density experiment

Dip an egg with a shell into a large-caliber glass filled with clear water. After releasing my hand, I found that the egg slowly sank to the bottom of the cup. Take out the eggs and add salt to clear water to prepare a high-concentration salt solution. Then immerse the egg in the salt solution, and after releasing the hand, the egg slowly floats.

The ups and downs of objects depend on the relationship between gravity and buoyancy. The volume of an object immersed in a liquid is the volume of the liquid it displaces. According to Archimedes principle, the relationship between object density and liquid density can correspond to the relationship between gravity and buoyancy. Because the density of eggs is slightly higher than that of clear water, when eggs are immersed in clear water, gravity is greater than buoyancy, so eggs will sink. When immersed in salt water, because the density of salt water is greater than that of eggs and gravity is less than buoyancy, eggs will float.

Fourth, how to distinguish between raw eggs and cooked eggs.

Choose a raw egg and a cooked egg with similar appearance and put them on a horizontal table. Rotate them in the same place with the same force. What can spin quickly is cooked eggs, and what stops after a few turns slowly is raw eggs.

There is liquid egg white in the shell of raw eggs. When the external force acts on the eggshell and rotates, the egg white remains still due to inertia, so there is friction resistance between it and the eggshell, which makes the whole egg only rotate slowly. The egg white in the cooked egg has solidified into protein, and the whole egg can rotate quickly when it rotates under the action of external force.

Fifth, the eggshell tumbler.

Choose a raw egg, make a hole in one end of the small head, and clean the egg white and yolk in the shell. Slide the weight along the hole. Take the big end of the eggshell as the bottom and hold the eggshell. Light a candle, drip candle oil, and seal the heavy object at the bottom of the eggshell. Candle oil can be sealed to about a quarter of the height of the whole eggshell. After the prepared eggshell is pushed down, the eggshell can stand up automatically. Be a "tumbler".

The weight of the seal at the bottom of the empty eggshell and the candle oil make the center of gravity of the whole egg close to the bottom of the eggshell, and the lower the center of gravity, the better the stability. When the eggshell tilts away from the equilibrium position, the center of gravity of the egg rises. Because the bottom of the eggshell is spherical, the egg body returns to its original equilibrium position under its own gravity.