Scientific knowledge around students
Scientific knowledge around primary school students
1 Why do you see lightning first and then hear thunder? Light waves travel faster in air than sound speed.
Who was the first Olympic champion in China? (Xu Haifeng)
Who invented glasses? (Luigi, bacon)
Why does the bicycle move? (Bicycle tires rub against the ground)
Whose title is the following? (Poet Fairy-Li Bai, Poet Sage-Du Fu, Shi Gui-Li He Landscape Poet-Meng Haoran, Pastoral Poet-Tao Yuanming)
What does the light of June revolve around? How long is a cycle? (Earth) (24 hours)
What are the three plains in China? (Northeast Plain, North China Plain, Middle and Lower Yangtze Plain)
How many earthquakes occur on the earth every year? (about 5 million times)
What is the smallest and coldest star? (Pluto)
10 What is the thickness of the earth? (atmosphere)
1 1 Why is there a black box on the plane? It is used to record all kinds of situations on the plane when the accident happened and help people understand the cause of the accident.
12 What are the customs during the Spring Festival? (Sweep the house, set off explosions, post Spring Festival couplets, eat New Year's Eve, etc. )
13 What animals can predict earthquakes? Cattle, horses, donkeys, rabbits, chickens, dogs, snakes, rats, dogs, cats, swallows, eagles, etc. )
14 What plants bloom first and then shed leaves? (Forsythia suspensa, Winter jasmine, Chimonanthus praecox, peach tree, pear tree)
15 How do bees make hives? Every worker bee has a wax gland at the waist, which can secrete wax. This wax becomes soft and tough after chewing in the mouth, and can be used to build a honeycomb.
Why is the 16 medicine bottle so light? Because light color can reflect light, dark color absorbs more light in the sun, and drugs are easy to deteriorate. )
17 who invented the steam engine? (Watts)
18 which dinosaur is the hardest? (Stegosaurus)
19 what is the blood of the earth? (magma)
What is the skeleton of the earth? (rock)
The scientific knowledge around you
1. Why do sunflowers always open to the sun?
There is a substance called "auxin" in the stem under the sunflower disk. This substance has the function of accelerating growth, and it will run to the backlight side every time it encounters light.
So when the sun rises, the stem of the sunflower immediately hides to the side of the backlight, as if the whole plant is bent in the direction of the sun.
Second, why do boiled eggs peel well after soaking in cold water?
Eggs are composed of eggshells, egg whites and yolk. The main component of eggshell is calcium carbonate. There is a thin eggshell membrane between eggshell and egg white. This is protein's gel. There is an air chamber (bubble) in an egg. The fresher the egg, the smaller the air chamber, and the larger the air chamber will be after a long time. When the egg is cooked, the air in the air chamber will expand, and some air will run outside the eggshell. After the eggs are cooked, they will be immersed in cold water immediately.
3. Why does an object expand when heated?
After an object is heated, with the increase of temperature, the movement of the molecules that make up the object gradually intensifies, so the distance between the molecules becomes wider bit by bit, that is, from the perspective of the whole object, the object becomes expanded. Also, the expansion rate of an object is determined by the object itself, and different substances have different expansion rates.
4. Why do the stars twinkle?
We see the stars shining, not because the luminosity of the stars has changed, but because of the occlusion of the atmosphere.
The atmosphere is between us and the stars. When starlight passes through the atmosphere, it will be affected by the density and thickness of the atmosphere. The atmosphere is not absolutely transparent, and its transparency will change according to its density. So when we look at the stars through it on the ground, we will see that the stars seem to be flashing.
5. Why is the sea mostly blue and green?
Looking at the sea, it is often found that the sea water is blue-green. However, when you pick up the sea water, it is transparent and colorless. It turns out that the seawater itself is not much different from the water we touch every day, and it is also transparent. The blue and green we see are actually the phenomena produced by the ability of seawater to absorb light. Only green light can be absorbed and reflected by seawater; When the sea water is deep, blue light is also absorbed, and the sea water looks blue.
6. Why do people's hair turn white when they get old?
There is a substance called melanin in our hair. The more melanin there is, the darker our hair will be. Without melanin, hair will turn yellow or white. When human beings reach old age, various functions of the body will gradually decline, and the formation of pigments will be less and less, so the hair will gradually turn white.
Scientific common sense around you
1. Why does sorbet get angry?
The reason why sorbet bubbles is because there is a lot of invisible water vapor in the outside air. When it comes to cold sorbet, it will liquefy into droplets when it is cold. It seems that the sorbet is bubbling.
2. Why do sunflowers always face the sun?
Sunflower stems contain a wonderful auxin. This auxin is very afraid of light. When exposed to light, it will go to the backlight side and stimulate the cells on the backlight side to multiply rapidly. Therefore, the backlit side will grow faster than the bright side, causing the sunflower to bend towards light.
3. Why do cicadas shed their skin?
Cicada's shell (exoskeleton) is hard and can't expand with the growth of cicada. When the cicada grows to a certain stage, the cicada's exoskeleton restricts its growth, and the cicada loses its original exoskeleton, which is cicada slough.
4. How do bees make honey?
Bees spit the collected sweet flower juice into an empty beehive. At night, they suck sweet juice into their honey stomachs to make it, and then spit it out and swallow it. It takes 65,438+000 ~ 240 times to make sweet honey.
5, hanging on the wall of the quartz clock, when the battery runs out and stops, its second hand often stops at the "9" position on the dial. This is because the second hand is most hindered by the large torque at the "9" position.
6. Sometimes, when tap water flows from the adjacent faucet, it occasionally makes bursts of noise. This is because the water pipe vibrates when the water rushes out of the tap.
7. When taking pictures on TV, turn off the camera flash and indoor lighting to make the picture clearer. Because the reflected light of the flash lamp and the illuminating lamp on the TV screen will interfere with the transmitted light of the TV picture.
8. At the same temperature, frozen meat thaws faster in water than in air. At the same temperature, hot nails cool faster in water than in air. A cup filled with boiling water cools faster when immersed in water than when immersed in air at the same temperature. All these phenomena show that water has better heat transfer performance than air,
9. When there is cold water in the pot, the water droplets attached to the outer surface of the pot bottom can only be dried up after a long time on the flame, and will only boil when it is dried up. This is because the water droplets, the pot and the water in the pot keep heat conduction, and the temperature is almost the same. As long as the water in the pot does not boil, the water droplets will not boil, and the water droplets will gradually be dried by evaporation on the flame.
10, out-of-shape mirror, the farther away from the mirror, the more out of shape. Because the image in the mirror is formed by the reflection of the silver-plated surface behind the mirror, uneven silver-plated surface or uneven glass thickness will lead to aliasing. The farther away from the deformed mirror, the more the reflected light on the silver-plated surface deviates from the normal position according to the principle of light amplification, and the more deformed the mirror is.
1 1. There are several small holes communicating with the outside world on the side of the gas nozzle of the natural gas furnace, but natural gas will not be ejected from the side holes, but only from the nozzle. This is because the air velocity at the nozzle is high, and according to the principle of fluid mechanics, the air surface pressure is lower than the atmospheric pressure outside the side hole, so the natural gas will not be ejected from the side hole of the nozzle.
12, after the balloon blows up, hold the mouthpiece with your hand, and then suddenly let go, the airflow in the balloon is ejected, and the balloon moves due to recoil. You can see that the route of balloon movement is tortuous. There are two reasons: first, the thickness and tension of the inflated balloon are uneven everywhere, which makes the balloon contract unevenly and swing around when it is deflated, thus the movement direction changes constantly; Second, the shape of the balloon is constantly changing during the contraction, so the air velocity on the surface of the balloon is also constantly changing during the movement. According to the principle of fluid mechanics, the air pressure on the surface of the balloon is constantly changing, so the balloon will swing.
13. Why does it make a "swish" sound when it is windy?
Once the strong wind touches the slender things such as wires or branches, it will make a "swish" sound. The slender whip shakes violently in the air, and the air vortex is formed behind the whip, which causes the air to vibrate and make a sound. The wind blows the branches for the same reason as waving the whip. When it blows at an acute angle or behind a gap, it will also form this vortex, making a "swish" sound, and depending on the strength of the wind.
14. Why do you see lightning first and then hear thunder? Light waves travel faster in air than sound speed.
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