一．Why does a thermos bottle keep warm?
Analysis: the thermos can be kept warm because of the structure of the bottle, which basically prevents three kinds of heat transfer: convection, conduction and radiation.
1. The mouth of the bottle is small and the cork is added to prevent the heat convection.
Because the heat convection is related to the surface area of the liquid, the larger the surface area, the faster the heat convection is, and the more the heat is lost, the faster the water temperature decreases.Therefore, the insulating bottles are done fairly small to reduce heat convection；A cork is added to the top of the bottle, which reduces the flow of gas on the hot water, cutting off the convection of the heat and preventing the convection of air inside and outside the bottle；The second is to make the high-energy molecules that escape the hot water collide with the cork and then go back to the original hot water to slow the loss of hot water.
2. The bottle is made of double glazing, vacuumed in the middle, preventing heat transmission.
The bottle is made of a thin layer of thin glass with a few millimeters between the layers，The air in the sandwich layer is pulled out to create a relative vacuum, and the top of the bottle is filled with a dry cork，This is done to prevent heat transmission.The reason is that glass, corks are hot bad conductors, vacuum can not transmit heat, so the heat in hot water is difficult to transmit.
3. The bottle was plated with silver to prevent thermal radiation.
The double-glazed surface of the bottle is coated with silver film to improve its surface smoothness and smoothness.Since the surface of the bottle is smooth, it will radiate from the inside and outside of the bottle to the surface of the bladder. And the more smooth the surface of the bottle, the more powerful it is.Therefore, the heat in hot water is also difficult to radiate through the smooth surface of the bottle, which is to prevent thermal radiation.
二. According to the sound of the inside of the bottle, why can you tell the good and bad of the bottle?
Analysis: when choosing a thermos bottle, people with experience often attach their ears to the sound of the bottle. The larger the "buzz", the better the quality of the bottle.Acoustics knows that the propagation of sound waves depends on the media, which means that a vacuum cannot transmit sound.Also, the sound waves are reflected when they encounter obstacles in the process of transmission.All around us, there are all kinds of sounds at all times, and some of these sounds are going to go into the bottle.When these sounds into the inside inside when you meet the very bright silver plating surface reflection will occur frequently in inside, not through the glass interlayer of high vacuum, then in the inside was formed strong hybrid noise back, this is the larger people hear "buzzing" sound.The higher the brightness of the silvered surface, the higher the vacuum level in the sandwich layer, the more the "buzzing" sound will be heard, the better the quality of the bottle. Conversely, the smaller the buzz, the worse the quality of the bottle.
三．Why, by the pitch of boiling water, can judge the discontent of the flood?
We can view the air in the thermos bottle as an air column.When pouring water into a thermos flask, the water hits the air column and makes a sound.When you start pouring water, because there is less water in the bottle, and the air inside it is long, the air column will be long, then it will vibrate slowly, and the frequency will be low, and the tone will be lower.Water pouring more more, inside the water level is higher and higher, its air is less and less air column is more and more short, namely the air vibration is more and more quickly, the frequency is more and more big, the tone is more and more high, so the sound will become more and more "sharp".
五. In the winter, just bought a thermos bottle or a long time unused thermos flask, pour boiling water, all is to pour a small amount of boiling water and shake a few times, then pour into boiled water, this is why?
The main purpose is to prevent the bottle from bursting.Because glass is a poor conductor of heat, if we put a lot of hot water to fill her soon in the low temperature of the vacuum flask, then the inside of the wall will be heated and rapid expansion, while the outer wall heat expansion, this makes the inside internal and external expansion are not synchronized, the inner glass expansion force and will be inside a burst.So, you try to pour a small amount of boiling water in the bottle, and shake a few bottles, make inside preheating first, stay inside, both inside and outside wall heat expansion, then pour boiled water in great quantities, it is not easy to broken inside.
六，If you don't fill the bottle with boiling water or pour some water out of a bottle filled with water, immediately plug the stopper and often see the cork jump up. Why?
Analytic: when thermos when filled with hot water, plug the plug, the air over the water bottle will meet thermal expansion, the gas pressure is greater than the outside air pressure inside, so there will produce a large force to plug to plug out;When poured some water from the bottle, with boiling water poured out of, there are also part of the cold air in succession to drilling in the vacuum flask, after the cork stopper tight, thermal expansion, cold air into the bottle to get so was out.Therefore, when pouring the water from the thermos bottle, gently place the cork on the top of the bottle to let the steam leak out a part, then cover the stopper so that the stopper won't jump up.
七，Why is it that when you empty the bottle and plug the stopper, the cork will be harder to pull out after a while?
Parsing: after pouring the water, plug the stopper immediately and the cork will seal the bottle well. After a period of time, the air in the bottle is cooled so that the pressure inside is less than the external atmospheric pressure, so the cork is harder to pull out.
八，Why do you use rare hydrochloric acid to remove scale?
Analysis: the use of a thermos bottle can form a layer of scale in the bottle. The scale is formed after the hard water is heated by non-pure water, such as calcium carbonate. Pour some dilute hydrochloric acid into the bottle and shake the bottle to make it even contact with the scale. After a while, the scale will be removed. Its chemical reaction equation is:CaCO3+2HCL=CaCL2+H2O+CO2↑.
九，Why are there three round black spots in the middle part of the bottle?
The three round black dots are colloidal particles. It is used to stabilize the glass of the bottle, to prolong the life of the bottle.
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