"Thermal Motion of Molecules" Internal Energy PPT Courseware 3

Description

"Thermal Motion of Molecules" Internal Energy PPT Courseware 3

1. Diffusion phenomenon

Definition: The phenomenon of different substances entering each other when they come into contact is called diffusion

Several conclusions

The higher the temperature, the more obvious the diffusion phenomenon

Diffusion occurs not only between gases and liquids, but also between solids.

Cause of diffusion: due to molecular movement

Explanation of diffusion phenomenon

It directly shows that the molecules that make up an object are always moving irregularly. The higher the temperature, the more violent the movement of the molecules.

Diffusion description: There are gaps between molecules

The cause of Brownian motion: When a large number of liquid molecules are constantly moving irregularly, the unbalanced impact on the particles suspended in them is the cause of Brownian motion. That is: the never-ending irregular motion of liquid molecules is the cause of Brownian motion.

Brownian motion is the observed random motion of suspended small particles (small enough), not the motion of molecules. But it indirectly reflects that gas and liquid molecules are constantly making irregular thermal motions.

Why does Brownian motion become more obvious the higher the temperature?

As the temperature increases, the movement of liquid molecules becomes more intense. The number of collisions between liquid molecules and particles will increase, and the effect of each collision will be stronger. This intensifies the imbalance of the particles being impacted by liquid molecules from all directions, causing the Brownian motion of the particles to become more intense.

summary

1. The phenomenon of diffusion is the result of the endless and irregular motion of the molecules of the object itself.

2. Brownian motion reflects the never-ending and irregular thermal motion of molecules inside a liquid or gas.

3. Brownian motion is the motion of suspended small particles, not the motion of molecules.

4. The intensity of Brownian motion is directly related to the temperature of the liquid or gas and the size of the small particles.

Regarding Brownian motion, the following statement is correct:

A. Brownian motion is the irregular movement of pollen molecules.

B. Brownian motion is caused by collisions between molecules within pollen particles.

C. The higher the temperature, the more obvious the Brownian motion.

D. Brownian motion is an indirect result of molecular motion.

"Brownian motion" is an important experimental fact explaining the motion of molecules. Then Brownian motion refers to: ( )

A: Movement of liquid molecules;

B: Movement of solid molecules suspended in liquid;

C: Movement of solid particles suspended in liquid;

D: Common motion of liquid molecules and solid molecules;

practise

1. Which of the following statements about Brownian motion is correct ( )

A. Brownian motion is molecular motion

B． Brownian motion is a reflection of the irregular motion of molecules that make up solid particles.

C. Brownian motion is a reflection of the irregular motion of liquid or gas molecules

D. The longer the observation time, the more significant the Brownian motion

E. Sunlight shines into the classroom from the gap, and the movement of dust seen in the sun is Brownian motion.

2. Regarding Brownian motion, which of the following statements is correct ( )

A. Brownian motion refers to the irregular movement of liquid molecules

B. Brownian motion is caused by the unbalanced attraction of liquid molecules to small particles.

C. Brownian motion is caused by the unbalanced impulse produced when liquid molecules collide with small particles.

D. When the size of suspended particles remains unchanged, the higher the temperature, the more intense the irregular movement of liquid molecules.

3. When observing Brownian motion under a microscope, the intensity of Brownian motion ( )

A. It is related to the size of suspended particles. The smaller the particles, the more intense the Brownian motion.

B. It is related to the molecular size of suspended particles. The smaller the molecules, the more intense the Brownian motion.

C. It is related to temperature. The higher the temperature, the more intense the Brownian motion is.

D. It is related to the length of observation. The longer the observation time, the flatter the Brownian motion becomes.

4. The reason why larger particles do not undergo Brownian motion is ( )

A. Liquid molecules stop moving

B. The liquid temperature is too low

C. There are more molecules colliding with the particles, and the collisions in all directions balance each other.

D. The molecular impact force is difficult to change the motion state of large particles.

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Update Time: 2024-11-20

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