"Internal Energy" PPT courseware 3

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"Internal Energy" PPT courseware 3

1. Internal energy

Since ancient times, people have been searching for some kind of energy related to heat.

Is "heat" a kind of energy? Does it work?

1. Molecules have kinetic and potential energy

The molecules that make up matter are constantly undergoing thermal motion and also have kinetic energy, and the interaction between molecules gives them potential energy.

2. internal energy of object

The sum of the kinetic energy of thermal motion and the potential energy of molecules of all the molecules that make up an object is called the internal energy of the object.

The unit of internal energy is Joule (J)

Mechanical energy is related to the mechanical motion of the entire object, and internal energy is related to the thermal motion of the molecules inside the object and the interaction between molecules, so internal energy is another form of energy different from mechanical energy.

2. Changes in the internal energy of an object

1. The internal energy of an object decreases when its temperature decreases, and increases when its temperature increases.

2. How to change the internal energy of an object

How do you increase the temperature of a 50 cm section of wire?

1. Heating with flame 2. Sunbathing

3. Rub with hands 4. Heat with hands

5. Rub it on the ground 6. Hit it with a hammer

7. Repeated bending 8. ……

Divide these methods into two categories. What are your principles for classification?

(1) Heat transfer can change internal energy

When heat transfer occurs, the energy in a high-temperature object decreases and the energy in a low-temperature object increases.

In the process of heat transfer, the amount of energy transferred is called heat, and the unit of heat is joules.

(2) Doing work can change internal energy

in conclusion:

When work is done on an object, the internal energy increases and the temperature rises.

When an object performs work on the outside, its internal energy decreases and its temperature decreases.

The nature of work changing internal energy:

The mutual conversion of mechanical energy and internal energy.

practice

1. During the experiment of "pumping air into a bottle containing a small amount of water", the teacher continued to pump air into the bottle, so that the pressure of water vapor in the bottle increased, and the internal energy of the water vapor ______ (fill in "increase" or "decrease"), temperature ______ (fill in "increase" or "decrease").

When the cork jumps up, you can see ______ inside the bottle. This is because the water vapor ______ the cork, and the internal energy ______ (fill in "increase" or "less"). Temperature ______ (fill in "increase" or "decrease"). Water vapor ______ forms small droplets. When the white mist does not disappear, if you immediately close the stopper and pump air into the bottle again, you will see ____________.

2. Among the following options, the change in the internal energy of an object is achieved through work ( )

A. On a hot summer day, put some ice cubes in your beer and it will become cooler

B． The water in the solar water heater tank is heated by the sun

C. When a car is running, the tires get hot

D. Strike a match, burn a match

3. NASA scientists believe that the "fireballs in the sky" phenomenon that appeared on the East Coast of the United States are due to asteroids entering the Earth's atmosphere. Ask students to try to explain this rare phenomenon.

Class summary

The concept of internal energy

What factors determine the amount of internal energy?

What are the two ways to change internal energy? What's the difference?

Keywords: Internal energy teaching courseware, New People's Education Edition ninth-grade physics PPT courseware, ninth-grade physics slide courseware download, internal energy PPT courseware download, .ppt format

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Update Time: 2024-11-13

This template belongs to Physics courseware People's Education Edition Ninth Grade Physics Complete Book industry PPT template

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