"Air" Mystery of Air PPT Courseware 3

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"Air" Mystery of Air PPT Courseware 3

1. Composition of air

Lavoisier concluded that air is composed of oxygen and nitrogen, with oxygen accounting for about 1/5 of the volume of air.

Experimental Investigation: Determination of Oxygen Content in the Air

Experimental steps

(1) Connect the instrument and check the air tightness.

(2) Add a small amount of water to the gas collecting bottle and mark it.

(3) Clamp the latex tube with spring clamps. After igniting the red phosphorus in the burning spoon, immediately reach into the bottle and plug the stopper tightly. Observe the phenomenon of red phosphorus burning.

(4) After the red phosphorus is extinguished and cooled, open the spring clamp and observe the experimental phenomena and changes in the water surface.

【Experimental phenomena】

① Red phosphorus burns, releases heat, and produces a large amount of white smoke.

②After cooling, open the spring clamp, and the water flows into the gas collecting bottle along the conduit. The volume of water entering the gas collecting bottle accounts for about 1/5 of the space inside the bottle.

think

After the water in the gas collecting bottle has risen to about 1/5, it cannot continue to rise. What does this mean about the properties of the remaining gas?

The remaining gas in the bottle is mainly nitrogen, which is insoluble in water, does not burn and does not support combustion.

think for a while

In the experiment, the volume of water entering the gas collecting bottle is often less than 1/5 of the volume of the gas collecting bottle. What may be the reason?

(1) The device is leaking;

(2) The amount of red phosphorus is insufficient;

(3) Open the water stop clamp before cooling to room temperature after the red phosphorus is extinguished;

(4) Some water remains in the pipe and does not enter the gas collecting bottle...

Classification of substances:

Mixture: A mixture of two or more substances,

Such as: air, sea water

Pure substance: composed of a substance, which can be represented by chemical symbols,

Such as: oxygen (O2), nitrogen (N2), carbon dioxide (CO2)

Which of the following substances are pure substances and which are mixtures?

(1) Clear river water, (2) Clear lime water,

(3) Mineral water, (4) Nitrogen, (5) Fresh air

(6) Distilled water, (7) Red phosphorus, (8) Ice and water coexistence

(9) Phosphorus pentoxide, (10) Carbon dioxide

Pure substance: (4) (6) (7) (8) (9) (10)

2. Air is an important natural resource

1. Nitrogen

Properties and uses of nitrogen

Nitrogen is a colorless and odorless gas that is difficult to dissolve in water; it is chemically inactive, cannot burn, and does not support combustion.

Nitrogen is a raw material for making nitric acid and fertilizers. It can also be used as a protective gas and as an anesthetic in medicine.

2. Oxygen

Properties and uses of oxygen

Can provide breathing

Such as diving, mountain climbing, medical emergency, aviation, etc.;

Can support burning

Such as steelmaking, aerospace, gas welding, liquid oxygen explosives, etc.

3. Rare gases:

Rare gases are used in airships, flashlights, liquid helium freezers, neon lights, etc.

Properties and uses of noble gases

Noble gases are colorless and odorless gases with very inactive chemical properties.

Rare gases are often used as protective gases and can also be made into a variety of electric light sources, laser technologies, etc.

Self-diagnosis test questions

1. What components do the following facts indicate in the air?

(1)Clear lime water becomes turbid in the air__________

(2) Mice can survive for a period of time in a closed container filled with air_______

(3) Biscuits will become moist _________ if left in the air for a period of time

2. The maximum volume fraction in air is ( )

A. Oxygen b. Nitrogen

C. Noble gases D. carbon dioxide

3. Among the following substances, which one is pure ( )

A. water vapor b. Sprite drink

C. Jiangte mineral water D. fresh air

4. In daily life, can you give examples of which substances are pure and which are mixtures?

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Update Time: 2024-10-20

This template belongs to Chemistry courseware Beijing Curriculum Reform Edition Ninth Grade Chemistry Volume 1 industry PPT template

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