"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 7

Description

"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 7

learning target:

1. Can tell what liquefaction is and give several examples of gas liquefaction in daily life.

2. Can name two methods of gas liquefaction, and know that heat will be released when liquefying

3. The basic knowledge of vaporization and liquefaction in this section can be answered smoothly.

Important and difficult points

Know some gas liquefaction phenomena and use gas liquefaction analysis to explain related physical phenomena

Study Tip: Water vapor in the air and when we exhale is invisible

Self-study questions:

1. Give several examples of gas liquefaction in daily life.

2. The two methods of liquefying gas are _____; _____ Liquefied petroleum gas is put into tanks using the _____ method

3. When gas liquefies, it will _____ heat

4. Why are steam burns often more serious than boiling water burns?

What are the liquefaction phenomena in life:

1. In winter, the “white air” we exhale

It is composed of a large number of small droplets formed when exhaled water vapor encounters cold air and releases heat to liquefy.

2. In winter, when we enter the bathhouse with our eyes on, the water droplets on the lenses

It is formed because the water vapor in the bathhouse exotherms and liquefies when it encounters the cold lens.

3. Autumn dew; clouds, rain, fog in the sky

It is formed because water vapor in the air encounters a drop in temperature and releases heat to liquefy.

Class exercises:

1. Write the names of the following changes in states of matter

(1) When you go out for a run in the morning in winter, you will exhale "white air" from your mouth. This is a ____ phenomenon.

(2) Ice and snow turn into water, which is a _____ phenomenon.

(3) When washed clothes are dried, it is a __________ phenomenon.

(4) Molten steel turns into steel ingots, which is a _________ phenomenon.

(5) In summer, water pipes often "sweat", which is a _____ phenomenon.

(6) When you open the lid of a boiling water pot, you can see water dripping from the lid. This is a ___ phenomenon.

(7) When people who wear glasses come into a warm room from outside in winter, water droplets often appear on the lenses. This is a ____ phenomenon.

2. Fill an uncovered beaker with water, heat it to boiling, and then use a strong fire to heat the water. At this time, the temperature of the water will be: ( )

A. Slowly increase B. No change C. Rapidly rising D. Unable to determine

3. Regarding the two vaporization methods of evaporation and boiling, which of the following statements is incorrect: ( )

A. All change from liquid to gas B. All need to be carried out at a certain temperature

C. Evaporation occurs on the surface of the liquid, while boiling occurs both inside the liquid and on the surface.

D． Both evaporation and boiling require heat absorption

4. Which of the following statements is correct: ( )

A. All gases can be liquefied by lowering the temperature

B. Liquefied petroleum gas is used to reduce weight

C. When boiling water, the "white gas" coming out of the spout is not small water droplets

D． In summer, the outer surface of water pipes is often wet. This is caused by water pipe leaks.

Section 3-3 Knowledge points on vaporization and liquefaction:

1. The change of a substance from a liquid state to a gaseous state is called _____; the change of a substance from a gaseous state to a liquid state is called _____; vaporization and liquefaction are mutually reversible processes. Vaporization requires _____ heat and liquefaction requires _____ heat;

2. The methods of vaporization include boiling and evaporation;

(1) Evaporation: The vaporization phenomenon that can occur at any temperature and only occurs in _____ of liquid _____. The speed of evaporation is related to:

A is related to liquid _____: the higher the _____, the faster it evaporates (water sprinkled in the room in summer dries faster than winter; clothes dried faster in the sun)

B is related to the size of the liquid _____. The larger the _____, the faster it evaporates (when cooling clothes, you should open the clothes to cool them; in order to dry the accumulated water on the ground quickly, you should sweep away the accumulated water);

C is related to the _____ of the liquid surface. The faster the air flows, the more _____ it evaporates (cool clothes should be kept in a ventilated place; turn on a fan to cool down in summer);

summary:

1. Vaporization is the process of changing a liquid state into a gaseous state, and vaporization absorbs heat;

2. Liquefaction is the process of changing gaseous state into liquid state, and liquefaction releases heat;

3． Factors that affect the speed of evaporation; evaporation has a cooling effect;

4. The endothermic temperature of a liquid remains constant when it boils; boiling point;

5. There are two methods of liquefaction: cooling and compressing the volume.

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Update Time: 2024-11-18

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

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