"Boiling" PPT

"Boiling" PPT

Part One: Boiling Phenomenon

Under certain external conditions, when the liquid is heated to a certain temperature, a large number of bubbles appear inside. The bubbles expand rapidly, release a large amount of steam after rising to the liquid surface, and the entire liquid vaporizes violently. This phenomenon is called boiling. If heating is continued, the temperature of the liquid no longer rises, and the temperature at this time is called the boiling point of the liquid.

water boiling and temperature

When water boils, why does the temperature of the water no longer increase? It turns out that although water continues to absorb heat when it boils, it also turns into water vapor and escapes into the air. At this time, as soon as the flame transferred heat to the kettle, it was immediately carried into the air by water molecules. If the heat of the water in the pot cannot be accumulated, the temperature will naturally not rise. Even if the firepower is increased, the increased heat will only turn more water into water vapor. However, there is a way to increase the temperature of water when it boils, and that is to increase the air pressure. Because the air pressure acting on the water surface always tries to prevent water molecules from running into the air. The higher the air pressure, the higher the temperature must be for water to resist the pressure and turn into water vapor, and the temperature of the water will also increase.

On the ground, the pressure experienced by any object is one atmosphere. The deeper you go from the ground, the greater the air pressure and the higher the boiling point of water. On average, for every 1 kilometer increase in depth, the boiling point of water increases by 37°C. On the contrary, the boiling temperature of water will decrease. It is difficult to cook rice in high mountains because the air pressure there is low and water boils at less than 100°C. If you boil water at the top of Mount Everest, the water will boil when it reaches about 72°C.

"Boiling" PPT, Part 2: Classroom Exercises

1. Let me fill it out:

1. I will use ___________ to record and organize information.

2. When we boil water, we often say "the water is boiling." The scientific saying is _________.

3. I know that when water is heated to a certain temperature, the water will ________. If we continue to heat the water, the temperature will be ________.

4. When the water is heated to boiling and the heat source is removed, why does the temperature not change immediately? I think:___________.

I also discovered: __________.

5. Before water boils, there will be some small bubbles coming out. These small bubbles are ___________.

6． When water boils, a large number of bubbles will appear. These bubbles are actually___________.

7. In daily life, we have also seen some liquids that can boil like water, such as _____, _____, _____, _____, _____, etc.

8. When water is heated to 100°C, the water will quickly turn into _____ and rush out of the water surface, causing the water to vaporize violently. This phenomenon is called boiling.

2. Be a good little judge:

1. As the water continues to evaporate and is heated, the temperature of the water will continue to rise. ( )

2. The flame of the alcohol lamp is divided into flame core, inner flame and outer flame. When heating objects, the outer flame is used. ( )

3. The alcohol lamp contains alcohol, which burns easily, so you must follow the instructions when using it to avoid danger. ( )

4. It can be seen from the evaporation and boiling phenomena of water that the form of water is not fixed, it can change. ( )

3. Scientific inquiry:

Put a pot of cold water on the stove. After a while, the kettle made a singing sound. When the kettle stopped singing, the water was about to boil. Where did the singing in the kettle come from?

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