"Melting and Solidification" Temperature and Physical State Changes PPT Courseware 2

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"Melting and Solidification" Temperature and Physical State Changes PPT Courseware 2

1. Three states and changes of matter

1. There are three states of matter: solid, liquid, and gas.

2. The change of matter from one state to another is called change of state of matter

3. melting and solidification

2. Explore the rules of temperature changes during solid melting

(1) Experimental device:

(2) Operation tips:

(1) Place the test tube containing the sea wave (height about 3cm) in a large beaker containing hot water (slightly lower than the melting point, the melting point of the sea wave is 48°C). The test tube is equipped with a thermometer and a stirrer (glass rod) to stir the sea wave at any time and record the temperature every half minute. (2) When the temperature of the sea wave approaches the melting point, slightly slow down the heating speed. Pay attention to the changes in the sea wave: the test tube wall begins → the sea wave gradually melts → the temperature basically remains around the melting point → after all the sea waves melt → the temperature continues to rise. Stop heating when it exceeds the melting point by approximately 10°C.

(3) Conduct experiments:

1. Explore the temperature changes of naphthalene and paraffin when they melt.

2. Fill in the data in the table below and draw the image on the graph paper

(4) Melting curve analysis of sea wave and wax:

① What is the state of the sea wave during the period of time corresponding to the AB segment curve? How does the temperature change?

② At which point on the curve does the sea wave begin to melt?

③ What is the state of the sea wave during the period corresponding to segment BC? Does the temperature change? Was the sea wave heated during this time?

④ What is the state of the sea wave in the time period corresponding to the CD segment? How does the temperature change?

⑤ How does the temperature of the wax change during the entire process?

Crystal melting characteristics:

It continues to absorb heat and the temperature remains constant as it melts.

Understand the crystal melting curve:

Indicates that the crystal has a fixed melting temperature, absorbing heat during the melting process, but the temperature remains unchanged.

For example, sea waves, ice, salt, and metals are all crystals.

Amorphous melting characteristics:

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.

3. Solidification

Analyze the solidification curve of sea waves

(1) The DE segment indicates that the sea wave is in _____ state, _____ heat (optional "suck" or "release"), and temperature ________.

(2) The EF segment indicates that the physical state of sea waves is __________, _____ heat, and temperature ________.

(3) The FG segment indicates that the state of the sea wave is ______, _____ hot, and the temperature ________.

1. There is a definite temperature when a crystal solidifies; there is no definite temperature when a non-crystal solidifies.

2. Freezing point: The temperature at which a liquid crystalline substance solidifies.

For the same crystalline substance, freezing point = melting point.

3. Crystal solidification conditions:

(1) Reach the freezing point;

(2) Continue to release heat.

practice

1. Read the melting point table in your textbook and determine the states of each of the following substances at different temperatures:

Mercury at -40°C __________.

Alcohol at -115℃ __________.

Tin at 237°C __________.

Aluminum at 700°C __________.

Naphthalene at 90°C __________.

Naphthalene ______________ at 80°C.

2. The figure shows the solidification images of two substances, A and B, where _____ is the crystal melt. The freezing point of the crystal melt is _____; the melting point of the crystal is _____.

3. Use an alcohol lamp to heat the ice-water mixture. Before the ice in the cup completely melts, the following statement is correct ( ).

A. The ice in the test tube cannot reach the melting point and may melt

B． The ice in the test tube can reach the melting point and melt

C. The ice in the test tube cannot reach the melting point, so it cannot melt

D． Ice in a test tube can reach its melting point but cannot melt

4. There are ice cubes in both basins A and B. There are more ice cubes in basin A and fewer ice cubes in basin B. Bowl A is placed in the sun and basin B is placed in the shade. The ice cubes in the two basins are are not completely melted, then ( ).

A. The temperature of the water in basin A is higher than that of basin B

B． The water temperature in basin B may be higher than that in basin A

C. The water temperature in both basins is the same

D． You can't tell, you have to use a thermometer to measure it.

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

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Update Time: 2024-10-06

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