"Internal Energy" Internal Energy PPT Download

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"Internal Energy" Internal Energy PPT Download

Part One: Guidance Design

Learning point 1 Internal energy

Material: Moving objects have kinetic energy, and molecules are constantly doing irregular thermal motion, so moving molecules also have kinetic energy, as shown in Figure 13-2-8(a). Just as a spring has elastic potential energy when it deforms, molecules that attract or repel each other also have potential energy - molecular potential energy, as shown in Figure (b).

think:

Question 1: What information does this material convey to us?

answer:______________________.

Question 2: The sum of kinetic energy and potential energy is called mechanical energy. The mechanical energy of an object is related to the mechanical motion of the entire object. So what about molecules? How to understand the kinetic energy and potential energy of molecules?

Answer: 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. Internal energy is related to the thermal motion of molecules inside an object and the interaction between molecules. Internal energy is another form of energy different from mechanical energy.

Learning point 2: Heat transfer and changes in internal energy

Experiment 1: In the cold winter, using a hot water bottle to keep warm, the body gradually warmed up, but the hot water bottle gradually became colder, as shown in Figure 13-2-9A.

Experiment 2: The master worker put the hot workpiece into cold water to "quench" it. The workpiece became cold and the cold water became hot, as shown in Figure B.

think:

Question 1: How did the internal energy of the object change during the experiment?

answer:_______________________________________________.

Question 2: In the experiment, how does the internal energy of the object change?

answer:_______.

Learning point 3: Changes in work and internal energy

Experiment 1: Use a saw to cut a section of wood. After sawing, touch the saw and the wood with your hand and find that the saw and the wood are very hot, as shown in Figure 13-2-10A.

Experiment 2: As shown in Figure B, put some hot water in a wide-mouth glass bottle, tighten the rubber stopper, and inflate the bottle. When the stopper jumps up, you will find "white mist" appearing in the bottle.

think:

Question 1: In Experiment 1, how did the internal energy of the saw and the wood increase?

answer:_____________.

Question 2: In Experiment 2, the "white mist" is caused by the liquefaction of water vapor in the bottle. What does this mean?

answer:______________________________________.

Internal Energy PPT, Part 2: Summary of Frequent Examinations

Type 1 Understanding of Internal Energy

Example 1 Which of the following statements about internal energy is correct ()

A. Each water molecule in hot water has a large internal energy

B． Ice below 0°C has no internal energy

C. As the temperature of a glass of water increases, the internal energy increases

D. The internal energy of water with a higher temperature is greater than the internal energy of water with a lower temperature

Typical Example 2 Four beakers of the same specifications are filled with water. The water volume and temperature are as shown in Figure 13-2-9. Regarding the internal energy of the water in the four beakers, which of the following is correct? ()

A. The internal energy of the water in beaker a is greater than the internal energy of the water in beaker b

B． The internal energy of the water in beaker c is greater than the internal energy of the water in beaker d

C. The internal energy of the water in beaker a is greater than the internal energy of the water in beaker c

D. The internal energy of the water in beaker d is greater than the internal energy of the water in beaker c.

Type 2 Changes in the internal energy of an object

Typical example 3 Among the following phenomena, the internal energy of an object is changed by doing work ()

A. Stones heating in the sun

B． When you hit a nail with a hammer, both the hammer and the nail get hot.

C. Heating warms the room

D. The temperature of vegetables placed in the refrigerator compartment drops

Type 3: Understand the relationship between temperature, heat, and internal energy

Example 4 Which of the following statements about temperature, internal energy and heat is correct ()

A. When an object absorbs heat and does no external work, its internal energy must increase.

B． When an object absorbs heat, its temperature will rise

C. The temperature of object A is higher than the temperature of object B. The internal energy of object A must be greater than the internal energy of object B.

D. As the temperature of hot water decreases, the internal energy does not necessarily decrease

Internal Energy PPT, Part 3: Class Feedback

1. Which of the following statements about internal energy is correct ( )

A. An object moving at zero speed has no internal energy

B． Internal energy is the sum of the kinetic energy and molecular potential energy of all molecules in an object that move randomly.

C. An object at 0°C has no internal energy

D. An object with a higher temperature must have greater internal energy than an object with a lower temperature

2. There are different ways to change the internal energy. As shown in Figure 2-1A, a small ball of cotton dipped in ether is placed in a thick-walled glass cylinder equipped with a piston. When the piston is quickly pressed down, the inside of the cylinder can be seen. The cotton burned. This is done through________

The method causes the air in the glass cylinder to _________ to increase, and the temperature rises, reaching the ignition point of the cotton, causing the cotton to burn.

Picture B uses __________ to heat the water in the test tube until it boils.

3. As shown in Figure 2-2, put a small amount of water into the bottle and plug it tightly with a stopper. We cannot see the water vapor above the water surface in the bottle. Inflate the bottle through the small hole on the stopper. When the stopper comes from the mouth of the bottle, When you jump up, you can see white mist appearing in the bottle. This is because when the air in the bottle pushes the stopper out, it does work on the stopper. Its own _________ decreases, and the________ decreases, making the water vapor________. This is what we see. of white mist. This experiment shows that the object ____________________.

4. In summer we often put drinks and ice cubes together to make iced drinks. This is because the __________ between the drink and the ice cube is different. There is a __________ between the two. The internal energy of the ice cube is __________ (optional "increase", "decrease" or "unchanged"), and the internal energy of the drink is __________. Can __________ (optional "increase", "decrease" or "unchanged").

5. Which of the following statements about heat is correct ( )

A. The same object contains more heat when the temperature is high

B． The greater the internal energy of an object, the more heat it contains and the higher its temperature.

C. Heat is always transferred from an object with high internal energy to an object with low internal energy.

D. Heat is always transferred from an object with a higher temperature to an object with a lower temperature

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Update Time: 2024-09-09

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