After the reaction between oxygen and phosphorus is completed, the reaction is terminated to continue.

The experimental results will not go wrong because the open system makes the outside air burn continuously due to negative pressure.

Supplementary answer: It's still a tight question. The former method is not closed at the initial stage of the reaction, and it is not a closed system no matter how fast it moves.

Phosphorus will burn in the air and emit white smoke, which is a chemical phenomenon that people have long known. Lavoisier tried to collect all this smoke in an ingenious way. He pointed out that thick smoke is a very fine white powder. He weighed it heavier than the original phosphorus. Lavoisier judged that phosphorus combined with air. How do they combine? So I designed an experiment: in

Close tightly

Burn phosphorus in a container and weigh each substance. He put the small dish containing phosphorus on the cork seat on the water, lit the phosphorus with red-hot wire and quickly covered it with glass. White smoke filled the glass cover, then went out and the water in the cover began to rise. After a while, the water level stopped rising. Lavoisier thinks that phosphorus may be used less, and it is impossible to combine with all the air in the hood. So he did more than a dozen experiments with more phosphorus, and the water level rose by the same height. He thought, "phosphorus only combines with one-fifth of the air." Is air a complex mixture? " Lavoisier studied the combustion of sulfur and found that sulfur can only combine with one fifth of the air.

-thank you. Lily is better than nature: chemical discovery and creative thinking (series of cultural quality education for college students), Anhui University Press, 2007, 165438+ 10, ISBN 97878103557.