"Vaporization and Liquefaction" PPT courseware

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"Vaporization and Liquefaction" PPT courseware

Part One: Exploring the Boiling Experiment of Water

1. Ask questions

1.What are the characteristics of water when it boils?

2. What conditions are needed for water to boil?

3. If the water continues to be heated after it boils, will the temperature get higher and higher?

2. Guess

(1) A large number of bubbles may be produced when water boils

(2) Water may need to absorb heat during boiling

(3) If the water continues to be heated while it is boiling, the temperature may not change.

(4) If heating is continued while water is boiling, the temperature may rise.

3. Design experiments

Tip: The key to a successful experiment is to shorten the time the water is heated before boiling.

plan:

(1) Less water is heated;

(2) Add a paper cover with holes on the beaker;

(3) The flame of the alcohol lamp is larger.

Vaporization and liquefaction PPT, Part 2 content: Observation phenomena:

1. What happens when bubbles rise before and during boiling?

2. What is the temperature change of water before boiling? If you continue to heat after boiling, will the temperature get higher and higher?

4. Collect facts and evidence

5. Draw conclusions

① Boiling is performed at a certain temperature, that is, below this temperature, the liquid absorbs heat and heats up, but does not boil; at this temperature, the liquid boils but does not heat up.

② Boiling occurs violently on the surface and inside of the liquid at the same time.

③Although the temperature does not change when the liquid boils, it absorbs heat.

The temperature at which a liquid boils is called the boiling point.

Conditions must be met for boiling to occur:

1. The temperature reaches the boiling point

2. Continue to absorb heat.

Vaporization and liquefaction PPT, Part 3: Boiling point is a characteristic of matter

Different substances have different boiling points

Can identify substances by boiling point

The boiling point of a liquid is related to the atmospheric pressure at the liquid surface

Different air pressures lead to different boiling points of the same liquid

The boiling point of water at standard atmospheric pressure is 100°C

Application:

Medical cryotherapy - applying low-boiling point liquid ammonia and other substances to the treatment area, using the liquid ammonia to vaporize and absorb a large amount of heat to freeze the local tissue, thereby destroying or removing the diseased living tissue.

Vaporization and liquefaction PPT, Part 4: Practice

1. When the water in the heating pot continues to boil, the "white gas" on the water is not obvious. If the fire suddenly stops, a lot of "white gas" will appear on the water. This is because ( )

A. The temperature on the water surface when boiling is higher than 100 ℃

B. Water does not evaporate when boiling

C. After the fire is stopped, the water begins to evaporate in large quantities.

D. After the fire is stopped, the temperature on the water surface is lower than 100°C, and a large amount of water vapor liquefies into small water droplets.

2. Among the four phenomena that produce "white gas" described below, one of the causes is different from the others. This kind of "white gas" is ( )

A. When you open the wrapping paper of popsicles in summer, you will often see the popsicles emitting "white gas"

B. In winter, "white gas" keeps coming out of the mouths of people outdoors

C. People who smoke spray "white gas" from their mouths

D. When you open the door of the refrigerator freezer in summer, a "white gas" will come out.

3. In summer, in rural areas where there are no refrigerators, people often put the food into the washbasin and float the washbasin in the water tank to prevent the food from spoiling. Which of the following statements is correct ( )

A. The water tank is made of sand and gravel, which has a small specific heat and has a heat dissipation effect.

B. The specific heat of water is large and the temperature rise is small.

C. The water in the water tank continues to evaporate and absorb heat, causing the temperature inside the tank to drop.

D. The liquefaction of water vapor around the water tank reduces the temperature inside the tank.

Keywords: Zhejiang Education Edition seventh grade science PPT courseware free download, vaporization and liquefaction PPT download, .PPT format;

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Update Time: 2024-11-22

This template belongs to science courseware Zhejiang Education Edition Seventh Grade Science Volume 1 industry PPT template

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