"Vaporization and Liquefaction" Temperature and Physical State Changes PPT Courseware 2

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"Vaporization and Liquefaction" Temperature and Physical State Changes PPT Courseware 2

Can the liquid and gas states be transformed into each other?

Experiment 1: Drop alcohol into a balloon or plastic bag, squeeze out the air and tie it tightly. Place in hot water. Please observe the phenomenon.

1. Vaporization and liquefaction

The process of a substance changing from a liquid state to a gaseous state is called vaporization and requires the absorption of heat.

The process of a substance returning from a gaseous state to a liquid state is called liquefaction and requires the release of heat.

1. Exploration: boiling of liquids

Notice:

1. Observe the phenomenon when water boils

2. The temperature during boiling and whether the temperature changes during boiling

3. Record the data and use the obtained data to draw the curve of the relationship between temperature and time when water boils according to the crystal melting curve.

Analyze data and images to draw conclusions

(1) Temperature change rules:

Before boiling, water absorbs heat and its temperature rises.

During the boiling process, the heat absorption temperature of water remains constant.

(2) Conditions for liquid boiling: reaching a certain temperature and absorbing heat.

in conclusion:

The physical characteristics of water when it boils are:

Water boiling is a violent vaporization phenomenon. At this time, a large number of bubbles rise and grow until the water surface bursts, releasing a large amount of water vapor. During boiling, water absorbs heat, but its temperature does not change.

Boiling is a violent vaporization phenomenon on the surface and inside of a liquid simultaneously.

Various liquids have a certain temperature when they boil. The temperature at which a liquid boils is called the boiling point.

Boiling conditions reach the boiling point and continue to absorb heat

2. Vaporization

We usually take out the wet clothes to dry after washing them, and the clothes will be dry after a while.

So where did that water go?

Evaporation is the slow vaporization of a liquid that can occur at any temperature and only occurs on the surface of the liquid.

1. Explore: Factors affecting evaporation speed

When washed clothes are dried, sometimes they dry quickly and sometimes they dry slowly. What does this mean? (Evaporation has speed and slowness.) So what factors affect the speed of evaporation?

What are some effective ways to dry washed clothes as quickly as possible?

Conclusion: Factors affecting evaporation speed

1. The temperature of the liquid is high or low, the higher the temperature. Evaporates faster.

2. The surface area of ​​the liquid. The larger the surface area, the faster it evaporates.

3. How fast the air flows on the surface of the liquid. The faster the air moves, the faster it evaporates.

way of liquefying

Lower the temperature of the gas

For example: rain, dew, and "white gas" near the mouth of the pot

Water droplets on window glass in winter

Water droplets on beverage bottles taken out of the refrigerator

volume of compressed gas

For example: butane gas in lighters

liquefied petroleum gas

Fuel in rockets (liquid hydrogen)

practice

1. A burn from 100°C steam is more harmful than a burn from 100°C boiling water. Why?

Answer: Because water vapor at 100°C liquefies on the skin and releases heat, people will be burned more seriously.

2. When your hands are cold in winter, "blow" into your hands with your mouth. (Blow slowly) your hands will feel warm. If you blow hard into your hands, not only will your hands not be warmed, but they will feel colder. They are all "qi" coming out of the mouth, so why do they feel different?

Answer: When breathing, because it is relatively slow, the water vapor in the mouth liquefies and releases heat when it encounters cold hands, so people will feel warm; when blowing hard, the evaporation of the water on the hands will be accelerated, and evaporation absorbs heat. So people will feel colder.

3. When the rocket is launched, in order to protect the launch chassis, a large pool needs to be built at the bottom of the launch tower. Why? What is a white air mass?

Answer: Water absorbs heat when it vaporizes, so it can protect the launch chassis. After a large amount of water vapor leaves the water, it liquefies when it encounters cold again, so a large amount of white gas appears.

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"Vaporization and Liquefaction" PPT courseware:

"Vaporization and Liquefaction" PPT courseware Part 1: Exploring the boiling experiment of water 1. Ask questions 1. What are the characteristics of water when it boils? 2. What conditions are needed for water to boil? 3. If the water continues to be heated after it boils, will the temperature get higher and higher? 2. Guess (..

"Vaporization and Liquefaction" PPT:

"Vaporization and Liquefaction" PPT Part One Content: Review Questions: 1. What is melting? What is solidification? 2. What is a crystal? What is amorphous? What is the fundamental difference between the two? 3. What are the states of existence of matter in nature? ... ... ...

"Vaporization and Liquefaction" Temperature and Physical State Changes PPT Courseware:

"Vaporization and Liquefaction" Temperature and Physical State Changes PPT Courseware Learning Objectives: 1. Master the definition of vaporization, know the two ways of vaporization 2. Understand the phenomenon of evaporation, know that evaporation requires heat absorption and refrigeration, and be able to master the influencing factors of evaporation 3. Understand liquid boiling..

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Update Time: 2024-11-22

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