"Internal Energy of Objects" PPT

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"Internal Energy of Objects" PPT

Part One: Thermal Movement

1. Matter is composed of particles such as ________, ________ or ions,

The particles that make up matter are constantly doing irregular ________.

____________________ inside an object is called thermal motion.

2. The higher the __________, the more intense the irregular thermal motion of molecules.

Phenomenon: Both glasses of water turn red, but hot water turns red faster than cold water

Conclusion: The higher the temperature, the faster the liquid diffusion (molecular movement).

Do moving molecules have kinetic and potential energy?

Moving molecules also have kinetic energy.

The higher the temperature, the faster the molecules move and the more kinetic energy they have.

Because there are interaction forces between molecules, there is also potential energy between molecules.

Internal energy of objects PPT, part 2: internal energy

1. What is internal energy?

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

① Internal energy is the energy that describes the thermal motion of a large number of molecules inside an object. For a single or a few molecules, it is meaningless to say how much internal energy it has.

②All objects have internal energy. Internal energy cannot be zero.

③Internal energy is closely related to the temperature of the object. So it is commonly called thermal energy.

④ Internal energy is related to the amount of material (number of molecules).

⑤The internal energy of an object is also related to the volume and shape of the object.

⑥When the state of an object changes, the internal energy will change accordingly.

2. All objects, regardless of temperature, have internal energy.

Try to explain: Whether it is a high-temperature object or a low-temperature object, it has internal energy.

Regardless of high-temperature or low-temperature objects, thermal motion of molecules inside the object always exists, so they all have internal energy.

Internal energy of an object PPT, Part 3: Changes in the internal energy of an object

1. Heat transfer can change the internal energy of an object.

①Conditions for heat transfer

Heat transfer occurs between two objects with different temperatures.

②The essence of heat transfer

Internal energy is transferred from a high-temperature object to a low-temperature object.

Or from a high temperature part to a low temperature part of the same object.

Heat can be used to measure how much internal energy is transferred.

③Results of heat transfer

Objects with high temperature release heat, and as the temperature decreases, the internal energy decreases;

As much heat is released, the internal energy is reduced.

Objects with low temperature absorb heat. As the temperature increases, the internal energy increases.

As much heat is absorbed, the internal energy increases;

2. Work can change the internal energy of an object.

① The external work done on the object can increase the internal energy of the object.

1. Press the thumbtack on one end of the disposable chopsticks, hold the chopsticks in your hand and rub the thumbtack back and forth on the rough cardboard, and then feel with your hands whether the temperature of the thumbtack changes?

When work is done on the thumbtack, the temperature of the thumbtack increases and the internal energy increases.

2. As shown in the figure, take a thick glass cylinder equipped with a piston, and place a small ball of cotton soaked in a small amount of ether inside the cylinder. Press the plunger quickly and see if the cotton ignites.

Compressing the ether gas does work on the ether, causing the temperature of the ether to rise and the internal energy to increase. When the ether ignition point is reached, the ether burns.

②When an object does work on the outside, the internal energy of the object will decrease.

③The essence of work

It is the process of mutual conversion between other forms of energy and the energy within an object.

Work can be used to measure how much internal energy changes.

3. Work and heat transfer are equivalent to changing the internal energy of an object.

The unit of internal energy is the same as the unit of work and heat, which is the joule.

Internal energy of objects PPT, part 4 content: practice

1. In each of the following situations, does the internal energy of an object increase or decrease?

What is the method of changing internal energy?

(1) When using a pump to inflate a bicycle, the wall of the pump becomes hot.

(2) When sharpening a knife with a grinding wheel, the tool becomes hot.

(3) When the gas in the gas storage tank sprays outward, the temperature of the tank wall becomes lower.

(1) (2) Internal energy increases and work is done (3) Internal energy decreases and external work is done

2. Which of the following statements is correct---( )

A. Ice cubes at 0°C have no mechanical energy

B. When an ice cube at 0℃ turns into water at the same temperature, the internal energy does not change.

C. An ice cube at 0°C is taken from the first floor to the upper floor. Assuming that the mass does not change, the mechanical energy of the ice cube increases and the internal energy increases.

D. Ice cubes at 0℃ have internal energy

3. Which of the following statements is correct----------------- ( )

A. The thermal motion of molecules stops at 0°C, so the object has no internal energy at 0°C;

B. Thermal motion of gas molecules is the most violent, while solid molecules have no thermal motion;

C. The greater the kinetic energy of an object, the greater its internal energy.

D. The higher the temperature of the object, the more intense the thermal motion of the molecules.

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Update Time: 2024-10-01

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