What is the function of the water added to the gas bottle before the introduction of the hot steel wool?

Question

This is part of a "Preparation and Properties of Oxygen" lab, where we must "demonstrate the collection of a gas by water displacement and to investigate the chemical and physical properties of oxygen".  We had to "roll a piece of steel wool into a cylindrical shape about 10 cm long and 0.5 cm in diameter. Take out the last bottle of oxygen and add enough water to cover the bottom to a depth of about 2.5 to 3.5 cm. Hold the steel wool with the tongs, heat it for a second or two with the bunsen burner and then thrust it into the oxygen in the bottle." When we put the hot steel wool into the bottle of oxygen, it sparked a lot, and the only thing that I know if if you don't add water or add enough water, the glass bottle will crack.

Phil · Accepted Answer

Glass cracks when there is a rapid temperature change that occurs unevenly throughout the glass. In this case, the inside of the glass would be heated quickly by the reaction, but because glass insulates well, the outside would only receive this heat very slowly. The inside glass would expand as it receives the heat, but the outside part would remain mostly the same size. This is what causes the glass to break. In this case, the water is absorbing enough of the heat from the reaction to prevent cracking. Water has a high specific heat, which makes it good for this task.

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What is the function of the water added to the gas bottle before the introduction of the hot steel wool?

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