Sulfur is burned in air to form sulfur dioxide gas, which dissolves in water. The dissolved gas produces sulfurous acid, lowering the pH and turning universal indicator solution red to simulate acid rain.

1. Place a small volume of water containing universal indicator in a beaker or flask.
2. Light a small piece of sulfur on a deflagration spoon or similar holder.
3. Lower the burning sulfur into the flask or hold it above the beaker so the fumes contact the indicator solution.
4. Observe the indicator solution changing color from green to red as sulfur dioxide dissolves and acid forms.

Sulfur burns in oxygen - Learn Science:

Combustion of Sulphur - Any Excuse for a Chemistry Experiment:

• Use a pH probe instead of universal indicator to measure the acidity change quantitatively.
• Extend the demonstration by showing how limestone (calcium carbonate) neutralizes the acidic solution, but gets eaten away in the process.

• Wear safety goggles, gloves, and a lab coat.
• Perform the experiment in a fume hood or well-ventilated area; sulfur dioxide is toxic and irritating to lungs and eyes.
• Handle burning sulfur with care to avoid spills or burns.
• Dispose of acidic solutions according to laboratory safety guidelines.

• What gas is formed when sulfur burns in air? (Sulfur dioxide, SO₂.)
• Why does the universal indicator turn red? (SO₂ dissolves in water to form sulfurous acid, lowering the pH.)
• How does this model acid rain in the environment? (Burning sulfur compounds from fossil fuels releases SO₂, which dissolves in atmospheric water, creating acid rain.)
• What environmental effects can acid rain cause? (Damage to plants, soil acidification, corrosion of buildings, harm to aquatic life.)