"The Composition of Matter" PPT

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"The Composition of Matter" PPT

Part One: Introduction of New Course

Have you ever eaten sugar cane?

Are you eating sugarcane peels, sugarcane juice, or sugarcane bagasse?

What does the sugarcane juice you eat taste like?

Why does it smell this way?

Sugarcane juice contains sucrose and water; sucrose and water are found in the vacuoles of plant cells.

What are the substances such as sugar and water present in sugarcane cells made of?

Can the water present in a cell, or a drop of water in a beaker, be divided into smaller pieces?

The composition of matter PPT, part 2 content: step-by-step learning

1. A molecule is a particle that constitutes matter.

Molecules are very tiny, much smaller than cells

⑴If someone were to count the number of water molecules contained in a drop of water, it would take tens of trillions of years to count one per second.

⑵ If you compare a water molecule with a ping-pong ball, the ratio of its size is like the ratio of a ping-pong ball with the earth.

⑶25 million water molecules are only 1 centimeter long when arranged, while the same number of table tennis balls are 750 kilometers long when arranged one after another, which is equivalent to the straight-line distance from Beijing to Nanjing.

2. There are gaps between molecules

Experiments show that the volume of the mixture is ________ the sum of the volumes of water and alcohol.

It can be seen that there are gaps between water molecules and alcohol molecules. When water and alcohol are mixed, different molecules enter the gaps between the molecules, so the total volume will decrease.

3. Molecules are in constant motion

The phenomenon of matter moving from one place to another due to the movement of molecules is called diffusion.

The higher the temperature, the faster the diffusion.

The composition of matter PPT, the third part: some applications of diffusion phenomena

diffusion of solids

The surface carburizing method of steel parts (to increase the hardness of steel parts) and the aluminizing method (to improve the heat resistance of steel parts) both utilize the diffusion phenomenon; in the semiconductor process, diffusion methods are also used to infiltrate trace amounts of impurities to achieve control semiconductor performance purposes.

diffusion of liquid

When making soup, add a few drops of soy sauce. Even without stirring, the entire soup will gradually be evenly dyed with the color of soy sauce and rich in the delicious taste of soy sauce. This is the result of the diffusion of soy sauce in the soup.

diffusion of gas

When we are cooking in the kitchen, we can smell the aroma of the food outside the house. Sometimes, when the oil in the pot is hot, people outside the kitchen can smell the aroma of the oil.

The composition of matter PPT, part 4: Can you explain? (Using a molecular perspective)

1. In August, we can smell the fragrance of sweet-scented osmanthus on campus.

Molecules are moving, which is a phenomenon of diffusion

2. Table salt can dissolve in water

There is a gap between molecules and molecules

3. Wet clothes can be dried

Molecules are moving and there is diffusion

4. When water freezes, its volume will ______ (become larger or smaller), which means that the gap between molecules is ______ (become larger or smaller).

5. Among the following examples, the one that cannot explain that molecules are constantly moving irregularly is:---- ( )

A. After opening the perfume bottle, the whole room is filled with fragrance.

B. When sweeping the floor, you can see a lot of dust flying under the sun.

C. Putting sugar into water makes the whole glass of water sweeter.

D. Many bacteria can be observed in action using a light microscope

Keywords: Zhejiang Education Edition seventh grade science PPT courseware free download, composition of matter PPT download, .PPT format;

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Update Time: 2024-09-29

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