"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 6

Description

"Vaporization and Liquefaction" PPT Courseware on Changes in State of Matter 6

learning target

1. Know what vaporization and liquefaction are.

2. Know the two ways of vaporization (evaporation and boiling).

3. Understand the phenomenon of boiling; know what boiling point is; understand the conditions and characteristics of boiling.

4. Understand evaporation; know that evaporation can cause cooling; understand the factors that affect the speed of evaporation.

Learn important and difficult points

Key points: 1. Understand the conditions and characteristics of boiling.

2. Understand the factors that affect the speed of evaporation.

Difficulty: Analyze and summarize the conditions and characteristics of boiling.

Review the past and learn the new

1. What are the definitions of melting and solidification?

2. What are the two types of crystals, and what are their important differences?

3. Crystals require __ heat and temperature ___ during the melting process, while amorphous materials require __ heat and temperature ___ during the melting process.

4. What are the conditions for crystal melting and solidification?

5. Should we use 0oC ice or 0oC water to cool objects? Why?

Classroom meets standards

For example, a certain substance starts to melt at 25℃, but does not completely melt until 75℃. I would like to ask: Is this substance crystalline or amorphous?

For example, in welding technology, how has solder changed? How does the temperature of solder change during the melting process?

For example, is it better to use 0℃ water or 0℃ ice to cool an object? Why?

For example, regarding melting, which of the following statements is correct ( )

A. Crystals absorb heat when melting, while amorphous crystals do not absorb heat when melting.

B. The crystal does not absorb heat when melting, so the temperature does not change

C. Heating an object does not necessarily increase its temperature

D． The temperature of crystalline and amorphous crystals does not change when melting.

1. Vaporization and liquefaction

Self-learning

Read the content on pages 58-61 of the textbook (boiling and evaporation) and complete the following pre-exercise questions.

1. Boiling refers to the ____ phenomenon in which liquid ____ and ____ occur at the same time.

2. In the process of water boiling, the temperature ___, but it must be constantly ___. The boiling point refers to _____.

3. Evaporation refers to ______, and evaporation only occurs in _____.

4. ___ and ____ are two ways of vaporization.

5. After rubbing alcohol on the back of your hand, the area where the alcohol is applied will feel cold. Why?

2. Explore: Boiling Characteristics of Water

Ask a question:

1. What are the characteristics of the temperature changes of water before and after boiling?

The temperature rises before boiling and remains constant after boiling

2. If the water continues to be heated after it boils, will the temperature get higher and higher?

3. What will happen if the alcohol lamp is removed after the water boils? Will it stop boiling immediately? What does it mean?

Will not stop boiling immediately, will stop boiling after a while

Analysis and Demonstration

1. What are the conditions for boiling? Reach boiling point, continue heating

2. What are the characteristics of boiling? Absorb heat but the temperature remains unchanged

3. How does the size of bubbles change before boiling and during boiling? Before boiling, it changes from large to small, and when it boils, it changes from small to large.

4. According to the boiling point table of liquids on page P60 of the textbook, what is the boiling point of water? Why is the boiling point of water different from what is given in the textbook when we did the experiment?

5. After the water boils and the alcohol lamp is removed, why does the water continue to boil for a period of time?

communication and evaluation

What are the reasons why experiments succeed or fail?

1. It may be that the temperature of the experimental water is too low

2. It may be that the outer flame of the alcohol lamp was not used to heat the water in the beaker during the experiment.

3. It may be that there is too much heated water in the beaker

Think about it, discuss it

If you apply some alcohol to the glass bulb of a thermometer, what will happen to the thermometer's reading?

First it falls, then it rises, and finally it remains unchanged.

When the alcohol evaporates, it absorbs heat, causing the thermometer's reading to decrease. When the alcohol evaporates, the thermometer's reading increases until it stabilizes.

2. What are the factors that affect the speed of evaporation?

(1) The temperature of the liquid. The higher the temperature, the faster it evaporates.

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

(3) The air flows on the liquid surface. The faster the air flows on the liquid surface, the faster it evaporates.

1. (2010 Linyi, Shandong) Please determine which of the following images belongs to the boiling image of water ( )

2. (2009 Henan) As shown in the figure, boil water in an open kettle. After the water boils and then continue to heat it with a strong fire, the temperature of the water will be ( )

A. Vaporization accelerates but the temperature decreases

B. It fluctuates with the size of the fire.

C. Gradually increase

D. unchanged

3. (2011 Heze) When drinking boiling water, people often blow air onto the water surface so that it does not taste too hot. This is because ( )

A. Blowing air onto the water surface accelerates the evaporation of water, and water evaporation absorbs heat, lowering the temperature of the water.

B. Blow cold air into the water to lower the water temperature

C. Blow gas to make the hot water sink and the cold water stay at the top.

D. None of the above statements are correct

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For more information about the PPT courseware "Changes in the State of Matter, Vaporization and Liquefaction", please click on the Changes in the State of Matter ppt, Vaporization and Liquefaction ppt tab.

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Update Time: 2024-07-06

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

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