"Sublimation and Sublimation" Material Form and Its Changes PPT Courseware

Description

"Sublimation and Sublimation" Material Form and Its Changes PPT Courseware

teaching objectives

1. Know what sublimation and sublimation are, and understand the phenomena of sublimation and sublimation in life.

2. Know that sublimation needs to absorb heat and sublimation needs to release heat.

3. Understand sublimation and sublimation through experiments, observation and analysis.

4. Appreciate the beauty and harmony of the changes in the six physical states.

Common physical phenomena in life

a. In the severe cold winter, clothes that have been frozen can be dried.

b. Mothballs placed in the kitchen will become smaller and smaller and eventually disappear.

c. In cold winter, there will be ice flowers on the inner surface of the window glass.

d. If the light bulb is used for a long time, the light bulb will turn black.

observe physical phenomena

Discuss, explore and communicate:

Before heating: Iodine is an object in ( ) state

When heated: iodine changes from ( ) state directly to ( ) state, provided that ( ) heat is used.

When cooling: iodine changes from ( ) state directly to ( ) state, provided that ( ) heat is provided.

in conclusion

1. Sublimation:

1. Definition: The direct change of a substance from a solid state to a gaseous state is called sublimation.

2. Conditions: Sublimation heat absorption---sublimation refrigeration.

2. Condensation:

1. Definition: The direct change of matter from gaseous state to solid state is called sublimation.

2. Conditions: (When exposed to cold) Condensation releases heat.

3. Example:

Look carefully at the following graphs and explain them

Solid carbon dioxide (dry ice) is made by compressing and cooling carbon dioxide gas. The temperature can reach minus 78.5℃. If it is placed in the air, it will grow ice-like beards as shown in the picture.

Analysis: When solid carbon dioxide sublimates in the air, it absorbs heat from the surrounding air. After the heat of water vapor in the surrounding air is absorbed, desublimation occurs.

Exercise: As the saying goes, "It's cold before frost and cold after snow." Use the relevant knowledge you have learned to explain it.

Because frost is small ice particles formed by the condensation of water vapor in the air. The condensation process requires heat release. The condition for water vapor to release heat into the air is that the temperature is lower than the water vapor temperature. Therefore, it can only be achieved when the temperature is low enough. , water vapor will condense into frost, because the temperature is low when frost occurs, and people often feel cold. The temperature in snowy weather is already low. After it snows, the snow absorbs heat from the surrounding air when it melts, causing the originally low temperature to further drop, so it is cold after snow.

Which of the following phenomena belongs to the sublimation phenomenon ( )

A. Clothes that were frozen outside in winter dried out. B. There was a layer of frost on the ground.

C. There is thick fog in the morning. D. The water sprinkled on the ground has dried.

Among the following phenomena, which one is sublimation phenomenon ()

A. The formation of dew B. The formation of rain.

C. The formation of frost D. The filament of the light bulb becomes smaller

After using the fluorescent lamp for a long time, the wall of the tube turns black because ()

A. The filament sublimates when heated, and the gas in the filament condenses on the tube wall.

B. Glass decomposes to produce black substances

C. The filament is evaporated by heat and then solidified when cooled.

D. The filament heats up, causing the glass near the filament to melt and turn black.

Operation:

Classwork: Questions 1, 2, 3, 4, and 5 on page p102.

Tutorial (preview):

1. After class, exchange the three-state changes of water to explain some water cycle phenomena in nature.

2. After class, exchange information on the water resources situation in our country and local areas, and learn about the water resources crisis faced by mankind.

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For more information about the PPT courseware "Material Forms and Their Changes, Sublimation and Sublimation", please click the Sublimation and Sublimation ppt tab of "Material Forms and Their Changes" ppt.

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Update Time: 2024-10-19

This template belongs to Physics courseware Guangdong and Shanghai version of eighth grade physics volume one industry PPT template

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