"Internal Energy" Mechanical energy, internal energy and their transformation PPT courseware 3

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"Internal Energy" Mechanical energy, internal energy and their transformation PPT courseware 3

Basic theory of the structure of matter

Matter is composed of large amounts of ______

The molecule is very _____. If the molecule is viewed as a small ball, the diameter of the molecule is only about __________

Molecules move irregularly in ________

Two different substances can spontaneously enter each other. This phenomenon is called _____. According to the phenomenon of diffusion, we can conclude that the molecules are _____

There are interactions between molecules

There are _____ interactions between molecules, and attraction and repulsion _____ exist between the molecules that make up matter. The strength of attraction and repulsion is related to the distance between molecules. When an object is stretched, the distance between molecules becomes larger, and the attraction between molecules becomes more significant; when the object is compressed, the distance between molecules becomes smaller, and the repulsion between molecules becomes more significant.

1. Understand the phenomenon of diffusion

Two different substances can spontaneously move into each other, a phenomenon called diffusion.

The diffusion phenomenon can be understood from the following five aspects:

(1) Different substances must be in contact with each other before diffusion occurs;

(2) The phenomenon of diffusion is not limited to different substances in the same state. Diffusion can occur between gases and liquids, gases and solids, and liquids and solids;

(3) The phenomenon of diffusion shows that molecules are constantly moving, and it also shows that there are gaps between the molecules of objects;

(4) The diffusion phenomenon is caused by the constant movement of molecules and does not occur under the action of macroscopic forces;

(5) The speed of diffusion is related to temperature. The higher the temperature, the faster the diffusion.

[Example 1] Among the following phenomena, which one can show that molecules are moving irregularly ()

A. Willow branches sway in spring B. Lotus flowers bloom in summer

C. Falling leaves are flying in autumn D. Snow is falling in winter

Analysis: The swaying willow branches, flying fallen leaves, and falling snow are all mechanical movements of objects, so options A, C, and D are incorrect; the fragrance of lotus flowers is the result of the non-stop irregular motion of floral molecules, so option B is correct.

2. Internal energy and changes in internal energy

Work and heat transfer are two ways to change the internal energy of an object.

(1) The essence of doing work to change the internal energy of an object is that other forms of energy are converted into internal energy.

(2) The essence of heat transfer that changes the energy within an object is the transfer of energy between objects.

(3) Work and heat transfer are equivalent in changing the internal energy of an object.

[Example 2] Various methods in the figure below can increase the internal energy of water. The correct classification is ()

A.(a,c,d)(b) B.(a,b)(c,d)

C.(a,d)(b,c) D.(a,b,d)(c)

Analysis: a is heating with an alcohol lamp, changing the internal energy of the water through heat transfer; b is stirring with an object, changing the internal energy of the water by doing work; c is doing work on the air, increasing the internal energy of the air and raising the temperature. , the air transfers the internal energy to the water, which changes the internal energy of the water through the method of heat transfer; d is the heat transferred from the electric heating wire to the water after energization, which changes the internal energy of the water through the method of heat transfer.

1. (2014•Guangdong) As shown in the figure, the desk lamp can be lifted after two lead blocks with smooth surfaces are in close contact. This shows that ()

A. There is repulsion between molecules

B. Gravity exists between molecules

C. There are gaps between molecules

D. Molecules are constantly moving irregularly

2. In corners where coal has been piled up for a long time, a thick layer on the ground and walls will turn black. Explained from the perspective of molecular kinetic theory, this is a ______ phenomenon. When red ink is dropped into cold water and hot water respectively, you can see that the hot water changes color faster than the cold water, indicating that the higher the temperature, the more irregular movement of a large number of molecules in the water.

3. Regarding liquids, which of the following statements is incorrect ()

A. Has a certain volume B. Does not have a certain shape

C. Fluid D. There are no gaps between liquids

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For more information about the PPT courseware "Mechanical Energy Internal Energy and Its Transformation into Internal Energy", please click the Mechanical Energy Internal Energy and Its Transformation ppt Internal Energy ppt tag.

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Update Time: 2024-06-21

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