"Air" The Mystery of Air PPT Courseware 2

Description

"Air" The Mystery of Air PPT Courseware 2

Warm up before class

Please give it a try:

Can you completely submerge a beaker with paper in water without the paper getting wet?

Thoughts and Discussions

Why can't water enter the beaker?

Air cannot be seen or touched. Can you think of other ways to prove the existence of air?

Do you know about air? What kind of knowledge do you have?

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, and thereafter various rare gases were discovered one after another.

Composition of air

student experiment

1. Light a candle and fix it in the sink.

Thinking: Why can candles burn?

2. Fill the water tank with water and cover the gas collecting bottle.

Observation: What phenomena do you see?

students thinking

1. Why do lit candles go out?

2. Why does the water surface rise?

Teacher guidance

Why might the experimental results be different?

1. The slower you put the gas cylinder in, the more the water rises - the air expands with heat and contracts with heat.

2. The burning of candles produces CO2, which will also affect the results.

in conclusion

The oxygen content in the air cannot be measured using a candle and a gas collecting bottle.

Teacher experiment

1. Take air in a glass tube as the research object, and add a plug to form a closed system.

2. Take out the white phosphorus and cut it into small pieces, dry it with filter paper and place it on the metal sheet.

3. Put the metal piece into the glass tube and heat it.

4. After the glass tube cools down, open the plug below the water surface and observe the phenomenon.

Experimental features

1. The reaction is always carried out in a closed system.

2. The temperature required for white phosphorus combustion is low (40°C), the reaction is fast, and the phenomenon is obvious.

3. The thickness of the glass tube is uniform, which is conducive to observing the rise of the water surface.

Air is an important natural resource

discuss

What does air do? Why is air a precious natural resource?

Nitrogen

What are the common uses of nitrogen?

Important raw materials for making nitric acid and fertilizers

Used as protective gas

Liquid nitrogen freezing anesthesia

Superconductivity

Filling food with nitrogen to prevent corrosion

Oxygen

Why is it called "nourishing Qi"? What are the common uses of oxygen?

Noble gases

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

Produce various electric light sources such as neon lights and navigation lights

Used as protective gas

Helium is used to fill lift-off balloons

Helium as refrigerant

for laser technology

Summary and summary

Air

1. Composition of air

2. Air is an important natural resource

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File Info

Update Time: 2024-07-03

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

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