Physical phenomena, experiments and demonstrations related to eggs in life

Physics is a subject based on observation and experiment. In teaching, consciously guide students to contact with real life and analyze physical phenomena; Making use of things around you and doing physics experiments can stimulate students' interest in learning and deepen their experience. This paper introduces a group of physical phenomena and experiments related to eggs.

1, liquid evaporates and absorbs heat.

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

Analysis: Because the newly caught eggshell is attached with a layer of water film, at the beginning, the water film evaporates and absorbs heat, which makes the temperature of the eggshell 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.

2. The essence of thermal expansion and cold contraction

Experiment: Soak the boiled eggs in cold water immediately and take them out after cooling completely.

Analysis: First of all, when an egg is soaked in cold water, the eggshell contracts directly when it is cold, while the temperature of the protein drops very little and the contraction is small. At this time, the eggshell is mainly contracted. 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.

3. Verify the existence of 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.

Analysis: 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.

4. Floating and sinking phenomenon

Experiment: Immerse an eggshell in 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.

Analysis: The ups and downs of an object 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.

5, inertia, friction and resistance phenomenon

Experiment: 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.

Analysis: 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. We used it. Do you think it's okay?