"Internal Energy" PPT Courseware 2

"Internal Energy" PPT Courseware 2

Review questions

1. What is kinetic energy? What is gravitational potential energy? What is elastic potential energy?

The energy an object possesses due to motion is called kinetic energy. Objects at high places have gravitational potential energy due to their gravity. The energy an object possesses due to elastic deformation is called elastic potential energy.

2. What do the examples of diffusion phenomena cited in the previous section illustrate?

It shows that the molecules of all substances are constantly moving irregularly. There are gaps between molecules.

3. What is the relationship between the speed of random movement of molecules and temperature?

The higher the temperature, the more violent the random motion of molecules.

learning target:

1. Know the internal energy of an object.

2. Know that heat transfer can change the internal energy of an object.

3. Know that work must be done to change the internal energy of an object.

Internal energy definition:

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

(1) Which objects have internal energy? Why?

All objects have internal energy. Because the molecules of all objects are constantly moving irregularly, they have kinetic energy. Molecules interact with each other and therefore have potential energy.

(2) What is the relationship between internal energy and temperature?

1. The higher the temperature

2. Factors affecting internal energy: temperature, volume, mass, state

(3) What is the difference between internal energy and mechanical energy?

Internal energy is the sum of the kinetic energy and molecular potential energy of all molecules inside an object that move irregularly, and has nothing to do with the overall motion of the object.

Mechanical energy is related to the mechanical motion of the entire object. For example, a ball thrown into the air has gravitational potential energy when it leaves the ground. It flies in the air and has kinetic energy. The kinetic energy and gravitational potential energy of the ball constitute the mechanical energy of the ball. At the same time, the molecules inside the ball are also undergoing irregular thermal motion, and there are interactions between the molecules, so the ball not only has mechanical energy but also internal energy.

1. Determine whether the following statements are correct?

1. As the temperature of an object increases, the internal energy increases ( )

2. A small glass of water and a large bucket of water have the same temperature and the same internal energy ( )

3. The internal energy of water at 20℃ must be smaller than that of water at 80℃ ( )

4. The internal energy of an object at 0°C is also 0 ( )

5. An object placed at rest on the ground does not have any form of energy ( )

6. The faster an object moves, the greater its internal energy ( )

2. Changes in the internal energy of an object

Want to discuss:

(1) How to change the internal energy of an object?

(2) What are some examples in life of changing internal energy by changing temperature?

Think about it\do it

There is a piece of iron wire. In what ways can you increase its temperature? (Increase its internal energy)

A. Put it in the sun; B. Rub it on stones; C. Put it in hot water; D. Put it on the fire;

E. Hit it with a hammer; F. Cover it with your hands; G. Bending it repeatedly with force; H. Electrify it.

Conditions for heat transfer: there is a temperature difference

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

When an object absorbs heat, its internal energy increases; when an object releases heat, its internal energy decreases.

Emphasis: When the internal energy of an object increases, the temperature does not necessarily increase (for example, ice at 0°C changes to water at 0°C); but as the temperature increases, the internal energy will definitely increase.

Fill in the blanks

1. The ways to change the internal energy of an object are _______ and _______.

2. The sum of _______________ and ______________ inside an object is called the internal energy of the object.

3. In winter, blowing into your hands with your mouth will warm your hands. This is to increase the internal energy of the hands in a _______ method, and its essence is that the internal energy is _______ between objects. Rubbing your hands can also warm your hands. , this is to use _______ method to increase the internal energy of the hand. In this process, _______ energy is converted into internal energy.

In the following daily life examples, the internal energy of an object is increased by doing work ( )

A. Pumping up bicycle tires, the pump gets hot

B． The temperature of the water put into the solar water heater rises

C. Lit firecrackers soar into the sky

D. Boil water in a kettle and the steam will lift the lid

Among the following phenomena, the internal energy of an object is changed through heat transfer ( )

A. The hands rub against each other and become hot.

B． Boil water in a stove, the temperature of the water rises

C. Cutting wood with a saw, the saw blade gets hot

D. Grinding a kitchen knife with a grinding wheel increases the temperature of the kitchen knife

Regarding temperature, heat, and internal energy, which of the following statements is correct ( )

A. The higher the temperature of an object, the more heat it contains

B． Ice at 0°C has no internal energy

C. When an object absorbs heat, its temperature does not necessarily increase

D. When work is done on an object, the temperature of the object must increase

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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