"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 3

Description

"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 3

learning target:

1. Understand what is vaporization phenomenon? What characteristics does it have?

2. Understand the two methods of vaporization.

3. Understand the boiling phenomenon, know what the boiling point is and the conditions for boiling.

4. Understand what evaporation is and know that evaporation can be used for refrigeration.

Review the past and learn the new

1. Complete the following fill-in-the-blanks

(1) The phenomenon of matter changing from ____ state to ____ state is called solidification, and the temperature at which crystals solidify is called __________.

(2) The freezing point of alcohol is -117°C. It is in the __ state at -115°C and in the __________ state at -120°C.

(3) When a steel block turns into molten steel, the steel block needs to be __ hot; when water freezes into ice, the water needs to be __________ hot.

(4) In winter, if you put a few buckets of water in vegetable cellars in northern rural areas, the vegetables will be less likely to freeze. This is because the water will heat up when ____, so the temperature inside the cellar will not be too __________.

Think about it:

In daily life, we often see such phenomena:

There are water droplets on the beer bottle taken out of the refrigerator, and after a while the water droplets disappear; the water sprinkled on the classroom floor disappears after a while; the wet clothes dried in the sun soon, where does the water on the clothes go? went?

Preview the text content on pages 58-61 of the textbook and complete the following test questions

1. The change of a substance from ____ state to ___ state is called vaporization, and vaporization requires ___ heat.

2. There are two ways of vaporization, namely _____ and _____.

3. Boiling is the simultaneous ____ vaporization of liquid ____ and ____. Various liquids have a certain temperature when they boil. This temperature is called ____.

The boiling points of different liquids are generally _______, and the boiling points are related to _____.

4. The conditions for liquid boiling are: (1) the temperature must reach ____; (2) continue to ____ heat.

5. Evaporation is a vaporization phenomenon that only occurs in liquid ____. It can occur at _____ temperature. The evaporation process of liquid requires _____ heat, so evaporation has _____ effect.

1. Vaporization:

(1) Definition: The change of a substance from a liquid state to a gaseous state is called vaporization.

(2) Features: The vaporization process continuously absorbs heat from the outside world.

2. There are two ways of vaporization: evaporation and boiling.

3. Boiling:

(1) Definition: It is a violent vaporization phenomenon that occurs simultaneously inside and on the surface of a liquid at a certain temperature;

(2) Conditions that must be met for boiling: ⑴The temperature reaches the boiling point. ⑵ Continue to absorb heat from the outside world;

(3) Features: During the boiling process, heat needs to be continuously absorbed from the outside world, but the temperature remains unchanged at the boiling point.

(4) Boiling point: The temperature at which a liquid boils.

Its level is related to the atmospheric pressure. When the air pressure decreases, the boiling point decreases, and when the air pressure increases, the boiling point increases.

Supplement: Use a paper pot to boil water. The paper pot will not burn because: the boiling point of water is much lower than the ignition point of paper.

4. Evaporation:

(1) Definition: Evaporation is the slow vaporization of liquid that can occur at any temperature and only occurs on the surface of the liquid.

(2) Characteristics: When evaporating, it needs to continuously absorb heat from the outside world, and the temperature gradually increases.

(3) Evaporation has a cooling effect: the liquid absorbs heat during the evaporation process, causing the temperature of the liquid and nearby objects to drop.

Class exercises:

1. Please determine which of the following images belongs to the boiling image of water ( )

2. The phenomenon of a substance changing from a liquid state to a ______ state is called vaporization. There are two forms of vaporization: ______ and ______. The boiling points of different substances are_(optional "same" or "different").

3. Boiling is the simultaneous violent vaporization of liquid _____ and _____. The temperature at which a liquid boils is called _____. The conditions for liquid boiling are: 1) reaching _____; 2) continuing to _____. Under ____, the boiling point of water is 100°C. The phenomena before water boils are: there are few bubbles, and the bubbles become _____ (larger, smaller) as they rise; the sound loudness _____; (larger, smaller) the temperature remains _____; (increase, decrease, unchanged). The phenomenon when water boils is: there are many bubbles, and the bubbles become _____ (larger, smaller) as they rise; the sound loudness _____; (larger, smaller); the temperature remains __; (increase, decrease, unchanged).

4. Boil water in an open kettle, make the water boil, and then continue to heat it with strong fire, the temperature of the water will be ( )

A. Gradually increase B. No change C. Gradually decrease D. Suddenly high and then low

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Update Time: 2024-10-03

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 1 industry PPT template

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