Non-metals burn into acids

The idea

Non-metals react with oxygen to form oxides that are acidic in nature; burning sulfur gives sulfur dioxide, which dissolves in water to form sulfurous acid.

Burning sulfur

Sulfur is a yellow non-metal. It burns in air with a blue flame. What does it turn into?

When sulfur burns in air, what is formed?

• A gas
• A shiny metal
• Nothing new

Burn, dissolve, test

Press the three buttons in order: burn the sulfur, dissolve the gas in water, then dip blue litmus paper.

Non-metal oxides

Non-metals react with oxygen to form oxides that are acidic in nature. Burning sulfur gives sulfur dioxide, which dissolves in water to form sulfurous acid.

An acid turns blue litmus paper red, so the solution is acidic. Compare: metal oxides are basic.

• Stage | What we find
• Sulfur burns in air (oxygen) | sulfur dioxide gas
• Gas dissolves in water | sulfurous acid
• The solution | turns blue litmus paper red

Notes

Non-metals react with oxygen to form oxides that are acidic. Sulfur burns to sulfur dioxide, which dissolves in water to make sulfurous acid and turns blue litmus red.

Check yourself

Burning sulfur in air forms...

Sulfur dioxide dissolves in water to form...

The solution turns blue litmus paper red. So it is...

Which statement is correct?

• sulfur dioxide gas — correct. Yes!
• magnesium oxide. That comes from burning magnesium.
• a shiny metal. Sulfur is a non-metal. It does not turn into a metal.
• sulfurous acid — correct. Yes!
• rust. Rust forms on iron.
• plain water. The solution is an acid.
• acidic — correct. Yes! An acid turns blue litmus red.
• basic. A base turns red litmus blue.
• neutral. A neutral solution changes neither colour.
• Oxides of non-metals are acidic. Oxides of metals are basic. — correct. Yes! Burning sulfur gave an acid. Burning magnesium gave a base.
• Oxides of non-metals are basic. Oxides of metals are acidic.. It is the other way round.
• All oxides are neutral.. Metal oxides are basic and non-metal oxides are acidic.