When sulfur is burned in water, it reacts with oxygen from the air to form sulfur dioxide (SO₂) gas. This gas then dissolves in the water, forming a solution of sulfurous acid (H₂SO₃).

Here's the breakdown:

1. Burning sulfur: Sulfur reacts with oxygen in the air to form sulfur dioxide.

* S + O₂ → SO₂

2. Dissolving in water: Sulfur dioxide dissolves in water to form sulfurous acid.

* SO₂ + H₂O → H₂SO₃

So, the substance produced from burning sulfur in water is sulfurous acid.