1、Physical Properties
2、Chemical Properties
（1）Combustion of Charcoal in Air and Oxygen
Procedure:
Observations: In air， it glows and emits heat. In oxygen， it emits a bright white light， emits heat， and produces a gas that turns limewater cloudy.
Conclusion:
（2）Combustion of Iron Wire in Air and Oxygen
Procedure:
Observations: In air， it glows but does not burn， and emits heat. In oxygen， it burns vigorously， sparks， emits大量 heat， and produces a black solid.
Conclusion:
Experimental Precautions:
a. Coil the iron wire into a spiral: This increases the contact surface area between the iron wire and oxygen and helps maintain the temperature required for iron wire combustion.
b. Attach a match to the lower end: The temperature at which the match burns reaches the temperature required for iron wire combustion.
c. Slowly insert the iron wire from top to bottom when the match burns out: This prevents the match from consuming oxygen. The heat generated by the burning iron wire causes oxygen to escape from the mouth of the collection bottle.
d. Place water or sand at the bottom: This prevents molten material from splashing and breaking the collection bottle.
（3）Candle Combustion
Procedure:
Observations: In air， it emits yellowish-white light and heat. In oxygen， it burns vigorously， emits white light
实验现象：
硫在空气中燃烧时会产生淡蓝色火焰，释放热量，产生具有刺激性气味的烟雾。而在氧气中燃烧时，它会产生明亮的蓝紫色火焰，同样释放热量，并产生一种无色、具有刺激性的气体。
结论：
由此可见，氧气是一种化学性质非常活泼的气体。它在氧化反应中提供氧，具有氧化性，是常用作氧化剂。
3. 氧气的应用
