"Changes in the State of Matter in Life and Technology" State of Matter and its Changes PPT Courseware 5

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"Changes in the State of Matter in Life and Technology" State of Matter and its Changes PPT Courseware 5

1. Water cycle in nature

Clouds, rain, snow, fog, dew, and frost are very common natural phenomena. They are all formed by changes in the physical state of water on the earth.

Fog is when water vapor liquefies into small water droplets when it encounters cold in the air. These small water droplets are suspended in the air and are called fog near the ground. It is a phenomenon of water vapor liquefaction.

Dew occurs when the water vapor in the air encounters cooler leaves before morning when the weather is hot, and liquefies into small water droplets that adhere to their surfaces. This is a liquefaction phenomenon.

Frost occurs when water vapor on the ground surface condenses directly into a solid state when it encounters temperatures below zero degrees Celsius.

2. Pressure cooker

1. Structure: pot body, lid, vent, safety valve, fusible piece

2. Principle: As the air pressure in the pot increases, the boiling point increases.

When it first starts working, the vent hole is blocked, the air pressure above the water increases, and the boiling point rises. When the air pressure above the water reaches a certain level, the gas in the pot can just lift the safety valve, the air pressure maintains a certain value, and the water reaches a higher boiling point, about 110---120°C.

3. The function of fusible sheet

It acts as a backup insurance to prevent the safety valve from malfunctioning.

Use a pressure cooker to cook porridge. After turning off the heat, cool the pot with cold water and remove the pressure limiting valve.

When you finally open the lid of the pot, you can see that the porridge in the pot is still boiling. This phenomenon cannot be seen in ordinary pots. Which of the following statements is correct ( ).

A. After the flame is turned off, the temperature in the pot quickly drops below 100°C, but the air pressure decreases after opening the pot lid, so it boils again.

B. After turning off the heat, the temperature in the pot is still higher than 100°C. Even if it is not cooled and the pressure limiting valve is not removed, the porridge is still boiling.

C. After turning off the heat, the temperature in the pot is still higher than 100°C. After cooling, the air pressure in the pot is lower than before. After opening the lid, the air pressure drops to one atmosphere, so it boils again.

D. Porridge has poor fluidity and is not easy to cool down. Even if you do not pour cold water on it or remove the pressure limiting valve after turning off the heat, the porridge will still boil for a long time.

3. Refrigerator

1. What are the main components of the refrigeration system in a refrigerator?

Evaporator, compressor, condenser

2. What are the characteristics of the refrigerant used in refrigerators?

Substances that are easily vaporized and liquefied.

3. How does the refrigerator achieve the purpose of cooling?

Vaporization in the evaporator absorbs heat, and liquefaction in the condenser releases heat.

4. Physical state changes in aerospace technology

1. What are the fuel and accelerant of the launch vehicle?

Liquefaction: The fuel of launch vehicles is often in a liquid state. It is formed by liquefying the gaseous state by compressing the volume. The liquid state is conducive to storing and storing a larger amount of fuel, as shown in the figure:

2. The "heat-proof clothing" for the return of the spacecraft

Melting, vaporization and heat absorption: When the satellite returns to the ground, it rubs against the air and the temperature rises. The ablation layer on the fairing will melt, vaporize and absorb a large amount of heat, thus protecting the rocket or satellite.

Question: What kind of special substance is coated on the outer surface of the fairing?

Substances that melt or vaporize easily.

[Example 1] There is a layer of material called an "ablative layer" on the surface of my country's "Shenzhou 5" return capsule, which can protect the return capsule from burning due to high temperatures when it returns to the atmosphere. The "ablative layer" can play this role , in addition to thermal insulation properties, due to ( )

A. It has high hardness and is not easy to burn.

B. Its surface is very smooth, which can reduce friction with air

C. It absorbs a lot of heat when melting and vaporizing

D. It can radiate heat into space

3. Analyze the phenomenon of “white gas”

△When I open the refrigerator door, white gas comes out.

△White breath comes out when breathing outdoors in the north in winter.

△When boiling water, white gas spurts out from the spout. .

△White gas comes out when the popsicle wrapper is torn open.

Reason: When water vapor encounters cold, it releases heat and liquefies to form small water droplets; later, the white gas disappears because the small water droplets absorb heat and vaporize to form water vapor.

4. Analyze the phenomenon of “sweating”

△If you take out a bottle filled with liquid from the refrigerator, the bottle will sweat.

△When taking a shower, the glass mirror in the shower room will sweat.

△When you enter the house from the outdoors in winter, your spectacle lenses will sweat.

Reason: Bottles, mirrors, and spectacle lenses were originally at low temperatures in a low-temperature environment. Later, they encountered high-temperature water vapor. The water vapor released heat and was liquefied, so they "sweated".

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"Changes in the State of Matter in Life and Technology" State of Matter and its Changes PPT Courseware 4:

"Changes in the State of Matter in Life and Technology" State of Matter and Its Changes PPT Courseware 4 [Observe] The existence form of water in nature, and recall the formation process. Ice, snow, rain, dew, clouds, fog, frost, hail [Exploration] 1. The formation of clouds Clouds: water vapor condenses into small ice crystals or liquefies..

"Changes in the State of Matter in Life and Technology" State of Matter and its Changes PPT Courseware 3:

"Changes in the State of Matter in Life and Technology" State of Matter and its Changes PPT Courseware 3 Changes in the State of Matter in Life and Technology 1. The cycle of water in nature. The formation process of rain, snow, dew, and frost. 2. Working principle of pressure cooker. 3. Working principle of refrigerator. The shape of rain...

"Changes in the State of Matter in Life and Technology" State of Matter and its Changes PPT Courseware 2:

"Changes in the State of Matter in Life and Technology" State of Matter and Its Changes PPT Courseware 2 Preview Tips Do you know how the white clouds in the blue sky are formed? What's the matter with the heavy fog you encountered? Do you know how dew and frost are formed? You know rain, snow, frost...

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Update Time: 2024-10-02

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