When an ordinary solution is heated, the point at which bubbles begin to produce is called?

When the kettle is boiling, there will be some small bubbles on the wall or bottom of the kettle, and the small bubbles will vaporize with the surrounding liquid, and the boiling phenomenon will occur with it as the center, and we can also call these bubbles vaporization nuclei. Water in convective heat transferBoiling pointIt's 100, but if you put it in the microwave and heat it up, the temperature will be much higher than 100 and the water hasn't evaporated. Due to the lack of the second condition for boiling in the water heated in the microwave oven, the vaporized nucleus, the superheated liquid that easily reaches or even exceeds the boiling point but does not boil, when small particles (coffee powder, etc.) are put into the superheated liquid at this time, they (small particles such as coffee powder) induce the generation of gasification nuclei, forming the phenomenon of instantaneous boiling.

Boiling is a phenomenon of violent vaporization that occurs simultaneously inside and on the surface of a liquid at a certain temperature. Boiling pointIt is the temperature at which the liquid boils, that is, the temperature when the saturated vapor pressure of the liquid is equal to the external pressure. Boiling point refers to the temperature at which a pure substance boils at 1 standard atmosphere.

The boiling point of different liquids is different. The boiling point changes with the change of external pressure, and the low pressure is also the low boiling point.

When the liquid boils, the saturated vapor pressure in the bubble formed inside it must be equal to the pressure exerted by the outside before the bubble can grow and rise, so the boiling point is the temperature when the saturated vapor pressure of the liquid is equal to the external pressure. The boiling point of a liquid is related to the external pressure. When the pressure of the liquid increases, its boiling point increases; When the pressure decreases; The boiling point decreases.

For example, the steam pressure in a steam boiler is about a few tens of atmospheres, and the boiling point of water in a boiler can be more than 200. For another example, when cooking rice in a high mountain, the water is easy to boil, but the rice is not easy to cook. This is due to the fact that the atmospheric pressure decreases with the increase in the topography and the boiling point of water also gradually decreases with the increase in altitude.

At an altitude of 1,900 meters, the atmospheric pressure is about 79,800 Pa (600 mm Hg), and the boiling point of water is that those with a low boiling point generally vaporize first, while those with a high boiling point are generally more difficult to vaporize.

Different liquids. At the same atmospheric pressure, the boiling point of different kinds of liquids is also different. This is because the saturation vapor pressure is related to the type of liquid.

At a certain temperature, the saturated vapor pressure of various liquids is also constant. For example, at 20, the saturated air pressure of ether is Pa (44 cm Hg) lower than the atmospheric pressure, and the temperature rises slightly, so that the saturated vapor pressure of the ether is equal to the atmospheric pressure, and the ether can be boiled by heating it to 35. If the liquid contains impurities, it will also affect the boiling point of the liquid.

The boiling point of a liquid containing solute is higher than that of a pure liquid, which is due to the fact that the gravitational force between the liquid molecules increases after the presence of a solute, the liquid is not easy to vaporize, and the saturated vapor pressure is also smaller. To make the saturation vapor pressure the same as the atmospheric pressure, the boiling point must be raised. Different liquids have different boiling points under the same external pressure.

The relationship between boiling point and pressure can be obtained from the Clausius equation. [1]

Reasons for the change in the size of the bubbles produced by the heating of water:

When the temperature at the bottom of the beaker is high, the temperature of the upper part is low, when the water at the bottom of the beaker is vaporized into bubbles, it encounters the water in the upper part, and the water temperature in the upper part is relatively low, so it will be liquefied into water in cold and cold, so that the bubbles are getting smaller and smaller.

When the water boils, the temperature of the water in the whole beaker is kept at 100 degrees, so the water temperature of the whole beaker is about the same, when the water at the bottom vaporizes into bubbles, and encounters the water at the same temperature in the upper part, the more water that comes is vaporized into bubbles, so that the bubbles become bigger and bigger. The above is why.

There is a physical change and a chemical change in the heating of water:

Water undergoes a physical change in the process of getting hot. At the same time, due to the problem of molecular structure and collision, the molecular spacing changes, resulting in a change in density.

The principle of water evaporation by heat is that the water molecules are constantly expanded by heat, and the water molecules do not decompose and do not produce new molecules, so it belongs to physical changes. The principle of water electrification is that water molecules are decomposed into hydrogen atoms and oxygen atoms after being electrified, and then combined to produce hydrogen molecules and oxygen molecules to form two new molecules, so it is a chemical change.

The bubbles after heating are due to the increase in temperature, the solubility decreases, and the dissolved air in the water escapes. Air bubbles contain air in them. The water is heated from the beginning until it boils.

When heated, the air rises, and the bubbles gradually become smaller, because the higher the water temperature, the lower the solubility, and some of the gas dissolves again. When boiling, the water vapor rises, and the bubbles gradually get bigger, because the higher you go up the water, the lower the pressure, the bigger the sparkling wine.

When heating cold water, when the temperature has not reached the boiling point, bubbles often emerge in the water, because with the increase of the temperature of the cracking delay, the solubility of the gas originally dissolved in the water decreases, so bubbles escape

Therefore, the answer is: the solubility of the gas decreases with the increase of temperature, and the solubility of the gas decreases with the increase of temperature

It's because of the solubility of the water, when it's cold, it's dissolved in it, it's dissolved in it, carbon dioxide, and so on, and when the temperature rises, the solubility decreases, and the gases in the water quickly saturate, and it's forced out of the water, which is why when you boil water (before it boils) you see the bottom of the water (the bottom of the pot). The bottom of the pot and so on) will bubble up for a reason, which is the most basic knowledge of chemistry in the third year of high school

Before boiling, the temperature of each layer in the window is different, the temperature of the water layer near the heating surface is higher, and the temperature near the water surface is lower. The bubble not only has the air pressure p. inside the bubble during the ascent processWith the decrease of water temperature and decrease, there is a part of the water vapor in the bubble condensed into saturated steam, the pressure is also decreasing, and the external pressure is basically unchanged, at this time, the external pressure of the bubble is stronger than the internal pressure, therefore, the volume of the bubbles on the rise will shrink in the process, when the water temperature is close to the boiling point, a large number of bubbles emerge, rising one after another, and quickly from large to small, so that the water oscillates violently, generated"The ruler is hum, hum"This is it"The water does not boil"The truth.

1.Observe the boiling water at home, when the water is heated, there are bubbles rising, and the bubbles contain (gas), which indicates that the temperature increases, and the solubility of the gas in the water (decreases).

2.Thermometer:

The principle of mercury thermometer is very simple - it is because of the heat rise and contraction of mercury, as for why not use water, because when the water is at 4 degrees, the heat expands and the cold also expands, and the expansion coefficient of mercury is relatively large, and the change is more obvious There is also alcohol inside, that is, the red kind The alcohol thermometer is suitable for measuring low temperature (about -78 +110 degrees), and the mercury thermometer is suitable for higher temperatures (about 15 300 degrees).There is also a kerosene thermometer.

Before boiling, the bubbles move from the bottom to the top, and the volume gradually decreases, and some of them may disappear When boiling, the bubbles move from the bottom to the top, and the volume gradually increases, until the liquid level bursts The sound is larger before (about 100db) and smaller after (about 95db) db=dB.

The reasons for the change in bubble volume before and after boiling are as follows.

When the water is heated unevenly, the bottom temperature is high, and after the bubbles (buoyancy) move upward, they encounter colder water, and a part of the water vapor liquefies into water, so the volume becomes smaller.

After boiling, the temperature is uniform, but after the upward movement, the water depth becomes smaller, the pressure (P=P liquid Gh) becomes smaller, and the pressure inside and outside the bubble should be kept the same (only in this way will it not break), the volume of the bubble becomes larger, and the bubble continues to have water vapor to reach the bubble in the process of rising, and the volume becomes larger.

I won't explain too much about the complexity of the sound.

Kindness. Can you describe the title?

Goo-goo

Boiling water does not sound, ringing water does not boil"Hawkers!

1) Water boil before in a beaker.

Water vapor in the bubbles produced at the bottom.

When it rises, it liquefies in cold, so the bubbles become smaller, and these bubbles are destroyed by water vapor;

2) As can be seen from the image, the boiling point of the water is 99 when it is boiling, and the temperature remains unchanged at 99; 1 standard atmosphere.

The boiling point of the water is 100, the boiling point is related to the air pressure, the higher the air pressure, the higher the boiling point, so at this time it is less than 1 standard atmosphere;

3) After the water boils, if the heating source is removed, the water will no longer absorb heat, and it will not be able to maintain the boiling state, so the heating should be stopped, and the sedan should be observed to see whether the water can continue to boil;

4) The purpose of collecting multiple sets of data in the experiment is to summarize and summarize the general laws and obtain reliable conclusions, so it is in line with the topic

So the answer is: (1) water vapor (2) 99; <；3) Stop heating; （4）①．

The reason why bubbles come out of water is that the solubility of the dissolved gases in the water decreases as the temperature of the water rises.

The bubbles contain carbon dioxide, oxygen, and chlorine (in the case of tap water).

When the weather is hot and sultry, the water temperature is high, the solubility of oxygen decreases, and the oxygen in the water body is insufficient, so the fish like to flow on the surface of the water, because there is more dissolved oxygen on the surface of the water (which water surface is in contact with the air).