"Air" The air around us PPT courseware 4

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"Air" The air around us PPT courseware 4

Knowledge point 1. What is air made of?

Lavoisier experimentally concluded that air is composed of oxygen and nitrogen

The device used by Lavoisier to study the composition of air

Determination of oxygen content in air

Experimental steps:

1. Connect the instrument and check the air tightness.

2. Light the red phosphorus, quickly put it into the bottle, and tighten the cork.

3. When the gas collecting bottle cools to normal temperature, open the water stopper.

Questions and reflections:

1. What is the purpose of adding a small amount of water to the gas collecting bottle first?

A. Prevent burning red phosphorus from splashing on the gas collecting bottle and causing the gas collecting bottle to explode.

B. Absorb the generated white smoke phosphorus pentoxide while cooling down

2. Why does the ignited red phosphorus need to be put into the gas collecting bottle quickly?

Red phosphorus releases heat when burned, and part of the air will be heated and escape (diffusion), (resulting in more than 1/5 of the volume of water entering).

3. Why do you need to cool down before opening the water-stop clamp?

Because when the temperature is high, the gas volume expands and the pressure is strong, which reduces the volume of water entering the gas collecting bottle, resulting in small experimental results.

4. What is the main component of the remaining gas in the gas collecting bottle? What properties does it have?

N2, insoluble in water, does not support combustion

Keys to a successful experiment:

(1) The device cannot leak;

(2) Add a small amount of water to the gas collecting bottle (to prevent the high-temperature melt from exploding the bottom of the bottle)

(3) Red phosphorus should be excessive

(4) After igniting red phosphorus, immediately put it into the gas collecting bottle and tighten the stopper.

(5) After the red phosphorus cools, open the spring clip

think about it

1. Summarize the experimental principles.

Answer: Red phosphorus is used to burn oxygen in the air in a closed container, so that the pressure in the closed container is reduced. Under the action of atmospheric pressure, water enters the container. Determine the volume of water entering the container, which is the volume of oxygen in the air.

2. In the experiment of measuring the oxygen content in the air using the combustion method, what are the requirements for the reactants?

Answer: (1) Substances can burn in the air and do not react with other components in the air; (2) The products after the reaction cannot be gases.

3. Based on the experimental phenomenon, what are the properties of the remaining gas in the analysis bottle?

Answer: Cannot burn or support combustion; cannot be dissolved in water

4. Can the "large amount of white smoke" generated after the burning of red phosphorus be called "large amount of white mist"?

Answer: No, smoke is solid particles; fog is small droplets.

Class exercises

1. Calculated by volume, the most abundant gas in the air is ( )

A oxygen B nitrogen

C carbon dioxide D rare gas

2. The volume of oxygen in 100 liters of air is approximately ( )

A 78 liters B 78% C 21 liters D 21%

3. The volume ratio of oxygen to nitrogen in the air is approximately ( )

A 4:1 B 1:4 C 1:5 D 5:1

Types, properties and uses of rare gases:

Types: Helium (He), Neon (Ne), Argon (Ar), Krypton, Xenon, etc.

Properties: Colorless, odorless, very inactive.

Purpose: (1) Protective gas

(2) Make electric light source:

(3) Laser technology;

(4) Hypothermic anesthesia

(5) Helium is used in inflatable balls or air boats (safer than hydrogen).

Governance:

1. Reduce the use of fossil fuels such as coal, oil, and natural gas (or perform desulfurization during combustion)

2. Vigorously plant trees and strictly prohibit indiscriminate logging.

3. Develop new energy sources such as: solar energy, hydrogen energy, wind energy, geothermal energy, etc.

4. Reduce industrial waste gas emissions, recycle, purify and reuse waste gas.

5. Government departments should make reasonable plans, set standards, and strengthen monitoring.

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Update Time: 2024-09-30

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

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