"Melting and Solidification" Changes in State of Matter PPT Courseware 9

Description

"Melting and Solidification" Changes in State of Matter PPT Courseware 9

1. Melting: The process in which a substance changes from solid to liquid.

2. Solidification: The process of matter changing from liquid to solid

Explore questions:

1. What conditions are needed for the melting and solidification of substances? Are the laws of melting and solidification of different substances the same?

2. Does a solid turn into a liquid all at once during the melting process or is there a process?

3. How does the temperature of a solid change during the melting process?

Conditions for crystal melting:

1. The temperature should reach the melting point.

2. Continue to absorb heat.

Solids without a certain melting temperature are called amorphous

Characteristics of amorphous melting: continue to absorb heat and the temperature continues to rise.

Understand the amorphous melting curve:

It means that amorphous crystals do not have a fixed melting temperature. The whole process attracts heat and the temperature continues to rise.

Rosin, asphalt, glass, etc. in nature are all amorphous.

The main differences between crystalline and amorphous are:

Crystals have a fixed melting point, while amorphous materials do not have a fixed melting point.

crystal solidification laws

1. The temperature of the crystal does not change during the solidification process. This temperature is called the freezing point;

2. During the solidification process, solid and liquid coexist;

3. The crystal only begins to solidify when it reaches a certain temperature;

4. The solidification process releases heat.

Knowledge summary

basic concept:

(1) Melting: The process in which a substance changes from solid to liquid.

(2) Solidification: The process of matter changing from liquid to solid.

(3) Crystal: a solid with a certain melting temperature.

(4) Melting point: the temperature at which the crystal melts.

(5) Amorphous: a solid without a certain melting temperature.

(6) Freezing point: the temperature at which crystals solidify.

melting and solidification

1. The concepts of melting and solidification:

1. Melting: The process by which a substance changes from solid to liquid.

2. Solidification: The process by which a substance changes from liquid to solid.

2. Explore the changing rules of temperature when solid melts:

1. The sea waves continue to absorb heat during the melting process, and the temperature remains constant.

2. Paraffin wax continues to absorb heat during the melting process, and the temperature gradually rises.

3． Understand the melting curve of solids.

3. Melting point and freezing point:

1. Crystal: A solid with a certain melting temperature.

2. Melting point: The temperature at which a crystal melts.

3． Amorphous: A solid that does not have a definite melting temperature.

4. Freezing point: The temperature at which a crystal solidifies.

5. The melting point and freezing point of the same substance are the same, while the melting points of different substances are different.

4. Melting absorbs heat and solidifies releases heat:

Any substance absorbs heat when it melts and releases heat when it solidifies.

choose

The group of the following substances that all belong to crystals is ( ):

A.Iron, salt, rosin

B. Aluminum, paraffin, glass

C. Ice, asphalt, rosin

D.Naphthalene, crystal, salt

Which of the following statements is incorrect ( ):

A. When any solid substance melts, it absorbs heat.

B. When the crystal melts, the temperature does not change

C. Any solid substance has a certain melting temperature. This temperature is called the melting point of the substance.

D. During the melting process of the crystal, although the temperature does not change, it still absorbs heat.

After an object absorbs heat, its temperature will be ( ):

A. It must rise

B. Must not change

C. It may rise or remain unchanged.

D. None of the above statements are correct

Discussion and practice

1. People often say that "if it snows, it becomes cold when it doesn't get cold." Does this statement make sense?

2. The lowest temperature in northern Heilongjiang Province of my country has dropped to minus 52.3 degrees Celsius. Can I still use a mercury thermometer at this time? What kind of liquid thermometer should I use?

Think about it?

1. The lowest temperature in Mohe in northern China reaches -52.3ºC in winter. Should I choose a mercury thermometer or an alcohol thermometer? Why?

2. Is the temperature of the ice-water mixture always 0ºC? Why?

3. What’s the meaning of “it’s snowing when it’s not cold but it’s snowing”?

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For more information about the "Melting and Solidification Changes in State of Matter" PPT courseware, please click the Melting and Solidification ppt Changes in State of Matter ppt tag.

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"Exploring the Characteristics of Melting and Solidification" Material Form and Its Changes PPT Courseware 2 Learning Objectives 1. Know what melting and solidification are. Understand the endotherms of melting and the exotherms of solidification. Know the characteristics of crystalline and amorphous melting and solidification. Understand the physical meaning of melting curves. 2. know..

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Update Time: 2024-07-30

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

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