"Air" The air around us PPT courseware

Description

"Air" The air around us PPT courseware

Have you thought about it?

Tie the mouth of an inflated plastic bag tightly with string. Then squeeze.

Activities and Inquiry

Put a plastic cup upside down in the water to form an air column. Prick the plastic cup with a needle. The cup will sink and the air will escape and the water will rise.

History of the discovery of air

1. A long time ago, people thought that air was just a single substance.

2. In the 1770s, Swedish scientist Scheele and British chemist Priestley respectively produced oxygen.

3. In 1774, French chemist Lavoisier experimentally proved for the first time that there were oxygen and nitrogen in the air.

4. At the end of the 19th century, British physicist Rayleigh discovered the rare gas argon. After that, various rare gases were discovered one after another.

1. What is air made of?

1. Lavoisier’s experiment to determine the composition of air

He concluded that air is composed of oxygen (O2) and nitrogen (N2), with oxygen accounting for about 1/5 of the volume of air.

2. Determination experiment of oxygen content in air

Experimental steps:

1. Check the air tightness of the device,

2. Ignite the red phosphorus in the burning spoon and quickly put it into the gas collecting bottle.

3. Wait until the red phosphorus in the bottle is completely burned, cool to room temperature, and open the water stopper.

3. Composition of air

Air is a mixture.

2. Mixtures and pure substances

1. Mixture: A substance that is a mixture of two or more substances.

Such as: air, sea water, river water, mineral water, etc.

2. Pure substance: composed of one substance.

Such as: oxygen (O2), nitrogen (N2), red phosphorus (P), water (H2O), carbon dioxide (CO2), phosphorus pentoxide (P2O5), etc.

Pure substances can be represented by special chemical symbols

Exercise 1: Among the components of air, the volume fraction accounts for approximately 21% ( )

A. Nitrogen B. Oxygen C. Carbon dioxide D. Rare gas

Exercise 2: Among the following substances, which one is pure ( )

A. Mineral water B. Clean air

C. Iodized salt D. Ice and water coexistence

Exercise 3: The former is a pure substance and the latter is a mixture ( )

A. Sugar water, white wine B. Orange juice, oxygen

C. Ice water mixture, salt D. Nitrogen, oxygen

Class summary

(1) Properties of nitrogen:

Physical properties: Nitrogen is a colorless and odorless gas, not easily soluble in water, and its density is smaller than that of air.

Chemical properties: The chemical properties of nitrogen are inactive and generally do not support combustion.

(2) Purpose of nitrogen

4. Rare gases

(1) Noble gases: mixtures.

Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe)

(2) Properties of rare gases:

Physical properties: Rare gases are colorless and odorless gases that are difficult to dissolve in water.

Chemical properties: The chemical properties of noble gases are very inactive and only react with a few substances.

(3) Uses of rare gases

4. Protect the air

discuss

What kind of air pollution has happened around you?

What harm will air pollution cause?

What can you do to protect the air that people depend on?

causes of air pollution

The smoke and exhaust gas emitted by factories, the exhaust gas emitted by cars, airplanes, and ships, and the smoke and dust exhaust gas emitted by residents' stoves contain many harmful substances and are the main sources of air pollution.

Exercise 1: Which of the following statements about the components of air is correct ( )

A. The red signal light is filled with nitrogen gas

B. What can make clear lime water turbid is nitrogen

C. In order to prevent food from deteriorating, oxygen is filled into the packaging

D. Plants continuously inhale carbon dioxide during photosynthesis

Exercise 2: Place an open gas collecting bottle on the table. Which of the following statements is incorrect ( )

A. The gas cylinder contains air

B. The substance in the gas collecting bottle is in gaseous state

C. There is nothing in the gas collecting bottle

D. The substance in the gas collecting bottle has no color

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Update Time: 2024-07-02

This template belongs to Chemistry courseware People's Education Press Ninth Grade Chemistry Volume 1 industry PPT template

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