Today at 15:40, the second lesson of "Tiangong Classroom" starts on time. On the Chinese space station, which is about 400 kilometers above the ground, the "space travel" trio Zhai Zhigang, Wang Yaping and Ye Guangfu once again showed the scientific mysteries of space to the world through live broadcasting on the Chinese space station.
The space teachers are here and ready for class! 丨CCTV News
In the first lesson of the "Heavenly Palace" class, space blossoms, double portraits, space turns... In the microgravity environment, the physical phenomena related to gravity disappear, and all kinds of wonderful scenes that have never been seen on the ground appear in the space environment.
In the second lesson, the three space teachers not only conducted magical space experiments, but also took everyone to visit the scientific and technological experimental equipment in the Tianhe core module. The ice pier is a "surprise joining" of this space teaching, showing the wonders of space with three space teachers.
The ice pier has also come to space丨 CCTV News
Space ice and snow experiments
The Beijing Winter Olympics and Winter Paralympic Games have just come to an end, and three astronauts are also "dreaming together" in space, making a "water ball" turn into a dream "ice ball" in seconds.
After Wang Yaping slowly squeezed out a crystal clear "water ball" from the water bag, he used the "magic wand" to gently touch it. Within a few seconds, the "water ball" quickly turned white, turning from the outside to the inside into an "ice hockey ball." But this "ice ball" is not ice, Wang Yaping held it in his hand, feeling a little hot.
"Water polo" seconds become "ice hockey" 丨 CCTV news
This "hot ice" is not actually ice, but sodium acetate crystal. The magic of "turning water into ice" is actually the process of crystallization of supersaturated solutions. Sodium acetate can be dissolved in water, but the amount dissolved is limited. The higher the temperature, the greater the solubility of sodium acetate, which means that the same amount of water can hold more sodium acetate.
However, as the solution slowly cools down, the solubility will gradually decrease, and the solution will gradually "not fit" sodium acetate. However, in the case of external stability, this state of being obviously unable to load and continue to be loaded will continue, thus becoming a "supersaturated solution". However, for the solution, this situation is unstable, and when it is subjected to external influences such as stirring and oscillation, the solute will crystallize and precipitate, forming an "ice"-like visual effect. This process also emits heat, so it also becomes "hot ice".
Sodium acetate crystallization process 丨 Wayne Schmidt/Youtube
This experiment can actually be completed on Earth, but if you want to get a "suspended hot ice", you still have to rely on microgravity in space. This also shows a unique feature of space experiments: "containerless experiments" can be achieved.
When doing experiments on the ground, the experimental material may be affected by the material and shape of the container. But in the containerless material test cabinet in space, the experimental material can be detached from the container and suspended in the air. A while ago, in the containerless materials experiment cabinet on the Chinese space station, the test of zirconium metal melting and solidification was completed.
Zirconium metal melting and solidification experiment in containerless material experiment cabinet 丨CCTV News
Microgravity not only frees the material from its shackles, but also makes the forces that are not significant on the ground more wonderful.
Liquid bridge
If the water balloon and water film have already made you marvel at how much the surface tension of water can be, then the liquid bridge in the second lesson makes the surface tension even more amazing.
Ye Guangfu first squeezed two water balls out of the liquid bridge plate held by Wang Yaping, and the water balls "stuck" to the surface and gently swayed like jelly. Wang Yaping then brought the two liquid bridge plates closer together, and the water on the plates merged into one. Wang Yaping gently pulled open the two liquid bridge plates, and a liquid bridge appeared in the two plates.
Liquid bridge experiment: Like a "water bridge" connecting two boards 丨 CCTV News
On the ground, if we dip some water droplets with two fingers, close them together and then slowly pull them apart, a liquid bridge will also appear. But because of the gravity on the ground, it was difficult for us to pull out a long bridge. In the microgravity environment, the liquid bridge can exist more stably.
The liquid bridge experiment also occupies a very important position in practical scientific research. Tiangong-2 is equipped with a liquid bridge thermal capillary convection experiment box, which can make a larger-scale liquid bridge to complete related scientific experiments.
The perfect advance of the ice piers
In addition to these two experiments, the space teacher also showed everyone the "water-oil separation" experiment and the "space parabolic experiment" in the microgravity state of space. The "Winter Olympic Top Stream" ice pier is also a friendship performance, completing an elegant "spacewalk".
After Wang Yaping gently pushed out the ice pier, the ice pier slowly moved forward, making a forward that conformed to Newton's first law: under the action of no external force, the moving objects always maintained a uniform speed forward.
Rush the duck! Ice Pier 丨 CCTV News
However, there is still a certain gas resistance in the space station, so Wang Yaping also stressed that the ice pier is almost uniform speed.
In the "water-oil separation" experiment, Ye Guangfu incarnated as an "artificial centrifuge", rotated the vial mixed with water and oil, and used the rotation method to use centrifugal action to make the water and oil in it separate again under microgravity conditions.
Centrifuges are also equipped in the space station, which can complete the separation and preparation of medical samples such as blood samples and urine samples.
In fact, every project in the space classroom shows the principles of practical scientific experiments in the space capsule from the most fundamental point of view. Scientific experiments on orbit are one of the important tasks shouldered by the Shenzhou 13 astronauts.
The space classroom only shows a corner of the mysteries of space, and the children who are attracted by the course may be the next to explore the universe.
After all, space exploration is never-ending.
Author: Owl
Edit: Odette
Video picture support: Cai Wenjuan
Seeing the astronauts in class again is very kind, we look at the smooth picture, can't help but think, how about the space network speed? Did you know that astronauts can also play games in the space station, let's see what's going on!
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![Left hand ice pier right hand snow Rongrong, 24-year-old "two gold kings" transformed into "small purchase experts"?[fig]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)