"Sublimation and Sublimation" PPT courseware on physical states and their changes

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"Sublimation and Sublimation" PPT courseware on physical states and their changes

【Experience】The phenomenon of sublimation and sublimation in life

Activity: Review life phenomena and think about the following questions.

(1) Clothes that are frozen in winter ________ (please fill in “yes” or “no”) to dry.

(2) The ice flowers on the window glass in severe winter are ________-state substances.

(3) The filament of a light bulb that has been used for a long time becomes ________, and the outer wall of the light bulb becomes _____.

Tips: (1) Will (2) Solid (3) Fine Black

pre-study questions

1.What are sublimation and sublimation?

2. What are the characteristics of sublimation and sublimation? What are the sublimation and sublimation phenomena in life?

Explore the sublimation and condensation of iodine

1. Experimental equipment:

Solid granular iodine, beaker, glass piece, asbestos net, alcohol lamp, matches, tripod.

2. Experimental design:

(1) Put some solid granular iodine in a beaker, cover the beaker with a glass piece, heat it on an asbestos mesh, and observe what happens in the beaker.

(2) Stop heating and observe what happens on the glass piece.

3. Experimental analysis:

Based on the above experimental phenomena, consider the following questions:

(1) In the experiment, when heating, the observed phenomenon is ______________,

______ (optional "yes" or "no") liquid iodine appears in the beaker,

From this we can conclude: ______________.

Tip: When heating, it is observed that the beaker is filled with purple iodine vapor, the solid iodine particles are decreasing, and no liquid iodine appears in the beaker. From this, it can be concluded that solid substances can directly become gaseous.

Reference answer: The beaker is filled with purple iodine vapor, and the solid iodine particles are decreasing at the same time

No solid substance can directly change to gaseous state

(2) In the experiment, what phenomenon occurred on the glass piece covering the beaker? What does this mean?

Tip: When the iodine vapor generated after heating encounters the glass piece, it will turn into iodine particles and adhere to it. There is no liquid iodine on the glass piece. It can be concluded that gaseous substances can directly become solid.

Reference answer: With iodine particles attached, gaseous substances can directly become solid

(3) When heated, solid iodine can directly change into gaseous iodine. When iodine vapor encounters a cold glass piece, it will directly change into solid iodine. From this, we can further draw the following conclusions: .

Tip: When heated, solid iodine can directly change into gaseous iodine, indicating that sublimation needs to absorb heat; iodine vapor will directly change into solid iodine when encountering a cold glass piece, indicating that sublimation needs to release heat.

Reference answer: Sublimation absorbs heat, sublimation releases heat

Knowledge summary

1. sublimation

(1) Definition: The process in which matter changes directly from _____ to _____.

(2) Features: Sublimation process _____.

(3) Example: The volume of camphor tablets is _____.

2. Condensation

(1) Definition: The process in which matter changes directly from _____ to _____.

(2) Features: Sublimation process _____.

(3)Example: ______________.

Test Points Sublimation Phenomenon in Life

[Typical example] (2012 Tai'an High School Entrance Examination) Clothes that are frozen in winter will dry directly even in an environment below 0℃. The physical state changes that occur are ()

A. Evaporate B. Melt

C. Sublimation D. Liquefaction

【Exquisite analysis】Choose C. Ice will not melt into a liquid state in an environment below 0°C, but clothes can dry out and directly change from a solid state to a gaseous state. This change in physical state is sublimation. So choose C.

[Method Summary] Judgment of sublimation and sublimation

(1) Determine whether the initial and final states of matter are solid or gaseous.

(2) Remember the common solid substances: ice (ice crystals), dry ice (solid CO2), frost, rime; the common gaseous substances: water vapor.

1. In March 2012, British scientists developed a "laser eraser" specifically used to remove black toner writing on white paper. Under laser irradiation, the black toner on the paper directly turns into high-temperature carbon vapor, and the writing disappears. This process belongs to the following physical state changes ( )

A. Melting B. Vaporization C. Liquefaction D. Sublimation

[Analysis] Choose D. Black carbon powder is solid. When irradiated by laser, the carbon powder absorbs heat and directly changes into gaseous carbon vapor. The material changes from solid state directly to gaseous state, so it is a sublimation phenomenon. So choose D.

2. Use dry ice to cool down food during transportation and prevent food from rotting and deteriorating. This is an application(　)

A.Dry ice liquefies exotherm B.Dry ice melts endotherm

C. Sublimation heat of dry ice D. Heat release of dry ice sublimation

[Analysis] Choose C. This question examines the application of sublimation. Dry ice is solid carbon dioxide, which sublimates easily. At the same time, it absorbs a large amount of heat from the surroundings and lowers the temperature of the food. So choose C.

3. As shown in the picture, under a standard atmospheric pressure, a student put ice cubes into an empty can and added an appropriate amount of salt, and stirred it with chopsticks for about half a minute; the temperature of the mixture of ice and salt water in the can was measured to be lower than 0°C. Experiment Sometimes there is white frost on the bottom of the can. Regarding the analysis of this experiment and phenomenon, the correct one is ( )

A. Salt makes the melting point of ice lower than 0℃, and the formation of hoarfrost is a phenomenon of sublimation.

B. Salt makes the melting point of ice higher than 0℃, and the formation of hoarfrost is a phenomenon of sublimation.

C. Salt makes the melting point of ice lower than 0℃, and the formation of hoarfrost is a solidification phenomenon.

D. Salt makes the melting point of ice higher than 0℃, and the formation of hoarfrost is a solidification phenomenon.

[Analysis] Choose A. This question examines the phenomenon of physical state changes in life. See what state the object changes from to what state, and judge based on the definition of physical state change. The temperature of the mixture of ice and salt water in the can is lower than 0°C. The water vapor in contact with the bottom of the can directly turns into a solid when cooled. The direct change from gas to solid is a desublimation phenomenon, so choose A.

On the 2013 Spring Festival Gala stage, dry ice (solid carbon dioxide) was sprayed to create "white mist" to enhance the atmosphere. Please use your knowledge of physics to explain the reason for the formation of "white fog" on the stage.

[Students’ own answers]

①The "white mist" on the stage is gas.

② Formed due to sublimation of dry ice.

[Teacher Comments]

①Incorrect: "White mist" is a small droplet formed by the liquefaction of water vapor in the air when it is cooled. It is a liquid.

②Error: The sublimation process of dry ice (solid carbon dioxide) absorbs heat, lowering the surrounding temperature, and the water vapor in the air liquefies into "white mist" when cooled.

【correct answer】

Solid dry ice absorbs heat and directly turns into gaseous carbon dioxide. This is the sublimation phenomenon of matter. Because the sublimation process of dry ice needs to absorb heat, it lowers the temperature of the surrounding environment. The water vapor in the air will liquefy into small water droplets when it is cold, thus forming "White mist".

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For more information about the "Sublimation and Sublimation States of Matter and Their Changes" PPT courseware, please click the Sublimation and Sublimation ppt State of Matter and its Changes ppt tag.

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Update Time: 2024-11-18

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