"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 2

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"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 2

(1) Vaporization:

The process by which matter changes from liquid to gaseous state.

Two ways of vaporization: boiling and evaporation

Ask a question

What are the characteristics of water when it boils? If you continue to heat water after it boils, will the temperature get higher and higher?

Purpose of the experiment: observe the phenomenon of water boiling and the temperature of water when it boils

Designing experiments and conducting experiments:

Install experimental instruments according to the experimental device diagram.

Use an alcohol lamp to heat the water until it boils.

experiment equipment:

Iron stand, alcohol lamp, matches, asbestos net, beaker, cardboard with a hole in the center, thermometer, water, stopwatch

review

1. Vaporization: Substance changes from ______ to _____

2. There are two ways of vaporization ______ and ____.

Discuss your understanding of boiling based on the picture on the right

1. During the heating process of water, the temperature continues to rise, and more and more "white gas" appears on the liquid surface.

2. When boiling, violent vaporization occurs in the water, forming a large number of bubbles, which rise and grow until the water surface bursts, and the water vapor inside is emitted into the air.

3. During the boiling process of water, although it continues to be heated, it maintains a certain temperature.

Exploration 1: What are the characteristics of evaporation? (Answer by comparing with boiling)

Temperature at which evaporation occurs: Can occur at any temperature

Where evaporation occurs: only on the surface of the liquid

How violently evaporation occurs: Slowly

The analysis concluded:

Evaporation is a slow vaporization phenomenon that occurs at any temperature and only on the surface of a liquid

observe

1. The thermometer is placed in the air and the reading is ____℃

2. Dip an appropriate amount of alcohol on the bubble of the thermometer, take out the thermometer and read it in the air. How will the reading of the thermometer change?

Liquid evaporation needs to absorb heat, which will cause the temperature of the object it is attached to to decrease and have a refrigeration effect.

Phenomenons that affect the speed of evaporation in life

Phenomenon 1: Wet clothes dry quickly when dried in the sun, but dry slowly in a cool or shaded place;

Phenomenon 2: Clothes dry quickly when they are opened to dry, but they dry slowly when they are lumped into a ball;

Phenomenon 3: Clothes dry quickly in windy weather in autumn, but dry slowly when there is no wind.

think about it

1. Breathe into your hands with your mouth. How do your hands feel after a few seconds? What about blowing?

2. Being burned by steam is more serious than being burned by boiling water. Do you know the reason now?

Gas releases heat when it liquefies. When boiling water or cooking, people who are burned by 100°C water vapor often suffer serious injuries, not only because of the high temperature of the water vapor, but also because of the heat released when the water vapor liquefies.

practice

1. Open the lid of the boiling water pot, and you can see water dripping from the lid. This water is formed when the steam of the boiling water encounters the cooler lid ____;

2. In the winter in the north, you can see people outdoors constantly exhaling "white air", which is the "mist" formed when the exhaled ____________ encounters the cold air______;

3. When a person wearing glasses goes from a cold outdoor to a warm indoor, the lenses will be covered with a layer of small water droplets. This is caused by the _______ heat in the room when it encounters the cold lenses.

4. When you open the door of the refrigerator, you can see some "white gas" coming out, which is caused by ____________________.

5. Which of the following phenomena in life belongs to the liquefaction process ( )

A. The ice and snow melt B. The clouds clear and the fog disperses

C. White breath came out of the mouth D. The water on the ground dried up

6. In medicine, when liquid ammonia and other substances are vaporized, a large amount of heat is used to freeze the local tissue and then remove it.

Observe carefully, you will find that when boiling water, there is no "white gas" in the place closest to the spout. Why?

Phenomenon 1: Wet clothes will dry out in the sun and will also dry out in the shade. Why?

Phenomenon 2: Wet clothes are lumped together. The outside of the clothes is dry, but the inside is not dry yet. Why?

Phenomenon 3: Now our autumn school uniforms need to be dried for a day after being washed. Why?

knowledge expansion

1. Liquid petroleum gas is liquefied by compressing the volume at normal temperature and then packed in cylinders for easy storage and transportation.

2. Our country’s rocket technology has entered the world’s advanced ranks. The fuel tank of the Long March 3 carrier rocket stores liquid hydrogen as fuel.

3. Students read STS: Refrigerator

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Update Time: 2024-09-06

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

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