"Melting and Solidification" PPT courseware on changes in the state of matter

Description

"Melting and Solidification" PPT courseware on changes in the state of matter

1. Three states and changes of matter

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

2. Changes between various states of matter are called changes in state of matter.

3． melting and solidification

1. Melting and Solidification

The process of a substance changing from solid to liquid is called melting.

The process of a substance changing from liquid to solid is called solidification.

Are there any rules in the process of melting and solidification?

Are the laws of change of different substances the same?

Experimental results:

The melting characteristics of Haibo: It melts at a certain temperature. It continuously absorbs heat but the temperature does not change during melting.

The melting characteristics of paraffin wax: there is no fixed melting temperature, it continuously absorbs heat and the temperature continues to rise when melting.

Understand the melting curve

(1) The material in segment AB is in a solid state, indicating the process of crystal endothermic heating.

(2) The material in the BC segment is in a solid-liquid coexistence state, indicating the crystal melting process, absorbing heat, and the temperature remains unchanged.

(3) The material in segment CD is in a liquid state, which means that the liquid absorbs heat and heats up.

(4) Point B means that the material reaches the melting temperature, but does not start to melt, and the material is completely in a solid state.

(5) Point C indicates that the crystal has just completely melted and the material is in a liquid state.

2. Melting point and freezing point

According to different melting laws, solids can be divided into crystalline and amorphous.

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

Crystals have a freezing point, while amorphous crystals have no freezing point.

1. In the figure, how do the segments EF, FG, and GH respectively indicate how the temperature changes? What state is matter in?

EF segment: The temperature decreases and the substance is in a liquid state;

FG segment: The temperature remains unchanged and the substance is in a state of solid and liquid coexistence;

GH segment: The temperature decreases and the substance is in a solid state.

2. The lowest temperature in northern Heilongjiang Province has reached -52.3℃. Can I still use a mercury thermometer at this time? What kind of liquid thermometer should I use?

Do not use mercury thermometers, use alcohol thermometers.

3. Melting absorbs heat and solidifies releases heat

Although the temperature does not change when the crystal melts, it must be heated. If the heating is stopped, the melting will stop immediately. That is, the melting process must absorb heat.

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.

Conditions for crystal melting:

(1) The temperature must reach the melting point;

(2) Continue to absorb heat.

Conditions for crystal solidification:

(1) The temperature must reach the freezing point;

(2) Continue to release heat.

Consolidation exercises

1. When you have the same mass of 0℃ water and 0℃ ice around you and need to choose one of them to cool the object, you will choose ( )

A. 0℃ water

B. Ice at 0℃

C. An ice-water mixture composed of half water and half ice.

D. Because the temperatures of water and ice are equal, the effect will be the same regardless of the choice.

2. Which of the following statements about crystals and amorphous is correct ( )

A. The crystal melting process needs to absorb heat, and the amorphous melting process does not need to absorb heat.

B. The temperature does not change when the crystal melts, but the temperature rises when the amorphous melts.

C. The temperature remains constant when both crystalline and amorphous melts

D. Crystals are transparent and amorphous are opaque.

3. On a certain day in Beijing, the temperature was -8℃, and a thick layer of ice formed on the lake. At this time ( )

A. The temperature of the lower surface of ice is 0℃

B. The upper surface temperature of ice is 0℃

C. The temperatures of the upper and lower surfaces of the ice are both 0℃

D. The water temperature at the bottom of the lake is -8℃

4. There are the following substances: copper, glass, rosin, ice, asphalt. Please divide them into two categories according to their melting characteristics: one type of substance is _________, whose characteristics are _______________; the other type of substance is _______, whose characteristics Characterized by___________.

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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.

"Melting and Solidification" PPT courseware:

Contents of the first part of the PPT courseware "Melt and Solidify": Three states of matter: Take water as an example: ice rain, white gas, fog, dew, frost, snow, hail Water vapor Solid state: ice, frost, snow and hail Liquid state: rain, fog, dew, white gas Gaseous state: water Vapor (invisible to the human eye) ... ...

"Melting and Solidification" PPT:

"Melt and Solidification" PPT Part 1 Content: State Changes Solid, liquid, and gaseous states are the three common states of matter. Solid state: such as aluminum, gold, silver, copper, iron, etc. are usually solid. Liquid state: such as water, vinegar, oil, etc. are usually liquid. Gaseous state: such as oxygen, hydrogen,...

"Exploring the Characteristics of Melting and Solidification" Material Forms and Their Changes PPT Courseware 2:

"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: 2024-10-13

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

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