"Sublimation and Sublimation" PPT Courseware on Changes in State of Matter 6

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"Sublimation and Sublimation" PPT Courseware on Changes in State of Matter 6

review review

Can matter change directly between solid and gaseous states?

Explore experiments:

Can the solid and gas states directly transform into each other?

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) Sublimation releases heat.

Introduction to dry ice

Dry ice is solid carbon dioxide existing at minus 78.5 degrees Celsius under atmospheric pressure.

Liquid carbon dioxide forms a solid state when cooled to -21.1°C and the pressure is 0.415Mpa.

Dry ice absorbs heat and can directly sublimate into gas

Common sublimation phenomena:

(1) Clothes that are frozen outdoors in winter can also be dried.

(2) The filament of incandescent bulbs becomes thinner after being used for a long time.

(3) The mothballs in the closet will get smaller and smaller and eventually disappear.

(4) Dry ice is used to make rainfall and create stage effects.

Common sublimation phenomena:

(1) In the cold winter morning, there are ice flowers on the inside of the glass window

(2) In late autumn morning, there will be a layer of frost on the ground

(3) The walls of incandescent bulbs will turn black after being used for a long time

(4) Frost on the popsicle paper in the refrigerator

1. Refrigerated food

2. Smoke on stage

How does the white fog on the stage form?

Dry ice powder is sprayed onto the stage and rapidly sublimates and cools down, causing the water vapor in the air to cool and liquefy into small water droplets to create "white mist" to enhance the atmosphere.

3. Artificial rainfall

dry ice fire extinguisher

One is to use dry ice to sublimate and absorb heat to reduce the temperature of the burning material to below the ignition point;

The second is to use the carbon dioxide produced by the sublimation of dry ice. The carbon dioxide covers the surface of the burning object to isolate oxygen and extinguish the fire.

summary:

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

Sublimation phenomenon: camphor tablets become smaller, frozen clothes dry, and the filament of light bulbs becomes thinner.

2. Sublimation: Substance directly changes from gaseous state to solid state, which is called sublimation. Condensation releases heat.

Sublimation phenomenon: the formation of frost, ice flowers on window panes, and the formation of rime. The light bulb went black.

3. Application of dry ice sublimation:

(1) Artificial rainfall (2) Stage smoke

(3) Refrigerated food (4) Forest fire fighting

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Update Time: 2024-09-04

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

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