Some problems in the experiment of "observing the boiling of water" 1. What's the advantage of using 70 ℃ hot water to start the experiment? 2. When the water boils, remove the alcohol lamp and the water will stop boiling. What conclusions can you draw from it? 3. Why do bubbles appear in water before it boils? 4. By analyzing the boiling curve of water, you can draw the following conclusion: I hope you can help me solve the problem It doesn't matter if you only know one of them. You can answer which ones you know

Some problems in the experiment of "observing the boiling of water" 1. What's the advantage of using 70 ℃ hot water to start the experiment? 2. When the water boils, remove the alcohol lamp and the water will stop boiling. What conclusions can you draw from it? 3. Why do bubbles appear in water before it boils? 4. By analyzing the boiling curve of water, you can draw the following conclusion: I hope you can help me solve the problem It doesn't matter if you only know one of them. You can answer which ones you know

1. Shorten the time of water boiling, that is to shorten the experimental time
2. The boiling of water is an endothermic process, so it must be endothermic continuously to keep boiling
3. There is a small amount of air dissolved in the water, mainly oxygen. After heating, the solubility of the gas decreases, so it overflows
4. The liquid temperature remains unchanged during boiling
In addition, bubbles will also be generated in boiling water, which is caused by boiling, not by the overflow of dissolved gas

In the experiment of "observing the boiling of water" (1) the purpose of this experiment is to observe () and ()

In the experiment of "observing the boiling of water" (1) the purpose of this experiment is to observe the phenomena and characteristics of water boiling

Boiling experiment of water
1. Before boiling: water from outside____ Heat, temperature____ There are bubbles at the bottom of the beaker
2. Boiling: formed at the bottom of the beaker____ Bubbles, rising, growing, break up to the surface of the water, and the steam inside is released into the air
3. In the process of boiling, the temperature of water is always the same_____ But it needs to be continued_________ .
Boiling: in_______ Under the liquid______ And_____ Simultaneous_______ Vaporization phenomenon
2. Boiling point: the boiling point of liquid is the same as that of liquid surface________ The boiling point of the same liquid at different pressures_______ What is the boiling point of water at standard atmospheric pressure_______ .
3. Conditions of liquid boiling 1_____________ 2._______________ .

1. Before boiling: water from outside_ Absorption_ Heat, temperature_ Up___ 2. When boiling, bubbles are formed at the bottom of the beaker_ Water vapor___ Bubbles, rise, become larger, to the surface of the water burst, the water vapor inside the air. 3. In the process of boiling water, the temperature of water is always the same_ Keep the boiling point____ But

Experiments on boiling water,
When doing the experiment of "observing the boiling phenomenon of water", a student's experimental steps are as follows: A. add water into the beaker, then put the beaker on the asbestos net of the iron platform, cover the cup with cardboard, insert the thermometer into the water through the cardboard hole, B. heat the beaker with alcohol lamp, and observe the thermometer's indication C. when the water temperature rises to about 90 ℃, record the water temperature every 1min, Until about 6 minutes after the water boils, D blows out the alcohol lamp with his mouth and cleans up the instrument. The wrong step number is: the answer is a and D, but I don't know the reason for A. tell me my opinion

D wrong, the way to put out the alcohol lamp is to cover it with a cap, then pick it up and cover it again. (pick it up again to prevent the burning alcohol vapor from entering the lamp and causing an explosion.) a right, add a paper cover to prevent heat emission

The purpose of this experiment is to observe the phenomenon of water boiling and the process of water boiling_______ 2) figure a
2) When installing and adjusting the experimental equipment, the scientific and reasonable order is: first adjust and fix___ (fill in M or N, the same below)
3) Figure B is the temperature of the water at a certain time during the experiment____ Figure C is a picture of boiling water drawn by three students. It is known that the air pressure at that time is the standard atmospheric pressure, and the correct one is_____ .

1. Temperature change
2,N,M
3, 85 ℃, B

About ice and water junior high school science problem! Urgent! Ask everybody to help!
There is a piece of ice floating in the bucket. When the ice melts into water, the height of the water surface will increase__ If there is a small stone in the ice, when the ice melts, the height of the water surface will be higher than the original__ (insert "up", "down" or "unchanged")
Why? Could you be more detailed? Thank you!

1. The buoyancy of ice is equal to the weight of its boiled water, that is, the weight of ice. Then the volume of water is the same as that of the original boiled water, so the height of water surface remains unchanged
2. The weight of ice and stone is equal to the weight of its boiled water, so the weight of ice itself is less than the weight of the boiled water, so the volume of water is less than the volume of the original boiled water, and because the density of stone is greater than water, the volume of boiled water discharged by stone is certainly less than its own volume, so the water surface drops

What is water made of?
There are macro and micro problems in junior high school science. Don't answer me what water is the spirit of all things
There are three different answers, three! One is indispensable!
The format of the three questions is
1. Water is made up of ()
2. Water is composed of () and ()
3. Water molecule is composed of () and ()

Water molecules
Hydrogen, oxygen
Two hydrogen atoms and one oxygen atom

On the density of water in junior high school science
When casting a machine part with iron, it is necessary to make a model of the part with wax. It is known that the mass of the model is 1800 g, and the density of wax is 0.9 * 10 cubic kg / m3. How many grams of iron is needed to cast such an iron part? (the density of iron = 7.9 * 10 cubic kg / m3)

1800x7.9 / 0.9 = 15800 (g)
A: it takes 15800 grams of iron to cast such an iron part

Junior high school science physics problems (about the density of water)
The label of a bottled Baijiu liquor produced by a distillery reads "500 milliliters 45 degrees". What is the quality of this bottle of wine? What is the density of this wine? (the degree of alcohol refers to the volume of alcohol in 100 ml liquor, and does not take into account the volume change in blending.

M liquor = ρ water × 55% × 500 + ρ alcohol × 45% × 500 (here ρ unit should be g / cm & sup3;, m liquor unit should be g, density table)
ρ liquor = m liquor / 500 g / cm & sup3;

Water in life
distillation
1. Distillation flask: the development of thermometer_______ Put it in the branch port of the distillation flask, and put small stone particles in the flask to prevent the liquid_______ .
2. Gas in condensing tube_________ Water comes in from below__________ Water comes out from above
3. In the rectification process, the liquid with low boiling point vaporizes first, and the steam is cooled in the condensing tube and then liquefied
4. Distilled water is produced by distillation, which belongs to_______ .
5. The principle of distillation: according to the composition of liquid substances_________ Different, low boiling point liquid first_______ After__________ A relatively pure liquid was obtained
6. Impurities dissolved in water can be removed by distillation
Whether the refined salt sample is pure and can pass the test______ If found in the crystal________ It indicates that there are other crystals in the salt sample.

1. Bubble, boiling
2. Cold water, hot water
3. Do you want me to judge
4. Industrial distilled water
5. Boiling point, vaporization, liquefaction
6. Do you want me to judge
Supplementary answer:
Filtration, solid