Finding oxygen percentage using Phosphorus

Question 1

How?

Answer 1

Place phosphorus on an evaporating basin which is floating on water

Initial level of water marked by waterproof pen or sticker

Bung is removed from bell jar and phosphorus is ignited with a hot metal wire

Bung put back in jar

White smoke fills (phosphorus oxide) and water level in jar rises

Smoke clears as the phosphorus oxide dissolves in water

When water stopped rising mark the level

Turn bell jar upside down - fill with water until levels that have been marked