"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 9

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"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 9

Think about it:

In the process of physical state change, can liquid and gaseous states also transform into each other?

Find it:

The water on the roadside dries up. water → steam

There is less water in the kettle on the stove. water → steam

There is dew on the leaves of the grass on the roadside in the morning. water vapor → water

There are small water droplets on the inner surface of the glass windows in the classroom in winter. water vapor → water

Summarize:

Vaporization: The process of a substance changing from a liquid state to a gaseous state is called vaporization.

Evaporation: The phenomenon of gentle vaporization at any temperature is called evaporation.

Boiling: The violent vaporization phenomenon that only occurs at a certain temperature is called boiling.

Obviously they are all different ways of changing from liquid to gas.

Establish a hypothesis

1. The speed of evaporation may be related to the temperature of the liquid

2. The speed of evaporation may be related to the surface area of ​​the liquid

3. The speed of evaporation may be related to the speed of air flow on the liquid surface.

Kind tips

The speed of evaporation may be affected by the temperature of the liquid, the surface area of ​​the liquid, and the speed of air flow on the liquid surface. In the experiment, we need to eliminate the interference of other factors other than the experimental object. This requires controlling the experimental conditions. Designing a control group is a commonly used control experimental condition. Methods. Except for the experimental subjects, all other factors between the experimental group and the control group should be the same.

Factors that affect the speed of liquid evaporation:

1. The higher the temperature of the liquid, the faster it evaporates.

2. The larger the surface area of ​​the liquid, the faster it evaporates.

3. The faster the air flows on the liquid surface, the faster it evaporates.

application:

Evaporation is closely related to our lives. Sometimes we should try to increase or speed up evaporation, and sometimes we should try to reduce or slow down evaporation. Can you give specific examples to illustrate this?

Give it a try

If you rub a cotton swab dipped in alcohol on your hands, what will happen to the alcohol? How do your hands feel?

When the thermometer bubble is dipped in alcohol, what happens to the alcohol? How does the thermometer reading change?

Evaporation absorbs heat

experiment

1. The thermometer is placed in the air and the reading is ______.

2. Use a fan to fan the thermometer that is not stained with alcohol. The reading is ______.

3. If you fan a thermometer dipped in alcohol, how will the reading change? ______.

4. How does it feel when you rub some alcohol on your skin? ______.

What conclusions can you draw from analyzing the above experimental results?

How does the human body regulate body temperature?

In summer, when you use an electric fan to blow air on people, you will feel cool. Some people say that this is because the electric fan blows cool air to cool people down. Some people say that this is because the wind blown by the electric fan accelerates the evaporation of moisture (sweat) on the skin and makes people feel cooler. Cool, who do you think is right? And design experiments to test your judgment.

practise:

1. Wet clothes will dry out after a period of time. This is actually the ______ process of water. It is a kind of ______ phenomenon in the change of physical state. It can be carried out at ______ temperature.

2. When people come out of the swimming pool and are blown by the wind, they feel very cool. This is due to ______. A glass of alcohol at 40℃ will continue to evaporate when the lid is opened, and the remaining alcohol temperature will be ______40℃ (fill in: higher than, lower than or equal to).

3. Fans make you feel cool in summer. This is because ( )

A. The wind blowing from the fan is cool

B. The wind blew away the heat from the body

C. The wind from the fan can speed up the evaporation of sweat and accelerate the absorption of heat from the human body.

D. Fans can lower the air temperature

4. A large number of facts show that ______ heat is required when a liquid evaporates, so evaporation has a ______ effect.

5. The phenomenon of a substance changing from a liquid state to a ______ state is called vaporization. There are two forms of vaporization: ______ and ______.

6. Which of the following statements has nothing to do with the evaporation speed of liquid ( )

A. The higher the temperature of the liquid, the faster it evaporates

B. The more mass of liquid, the faster it evaporates

C. The larger the surface area of ​​the liquid, the faster it evaporates.

D. The faster the air flows on the liquid surface, the faster it evaporates.

1. Characteristics of boiling:

⑴ Boiling occurs both inside and on the surface of the liquid

⑵ Boiling requires a certain temperature

⑶ Boiling is very violent

⑷Boiling requires heat absorption

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

3. Boiling conditions:

⑴The temperature reaches the boiling point

⑵Continue to absorb heat

discuss:

1. Being burned by 100℃ water vapor is much more serious than being burned by 100℃ water. Why?

2. When the water in the kettle boils, why is there no "white gas" visible in the section near the spout, but can be seen in the section above?

liquefaction

1. Question: What liquefaction phenomena have you seen in daily life?

2. Questioning: Do you know the conditions for the liquefaction phenomenon?

3. Experiment: Water vapor liquefaction experiment

Conclusion: All gases can liquefy when the temperature drops low enough.

4. Question: Is there any other way to liquefy gas?

5. Ether liquefaction experiment

6. Methods of gas liquefaction

Reduce the temperature

Compressed volume

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Update Time: 2024-11-22

This template belongs to Physics courseware Lu Jiao Edition Ninth Grade Physics Volume 2 industry PPT template

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