Char Sugar for Carbon
Heat sugar to reveal black carbon residue
What this lesson covers
Why it matters
Pour concentrated sulphuric acid on white sugar and watch it violently expand into a black, spongy tower. The sugar doesn't just burn; it is stripped of its water.
The idea in plain words
Analyze the decomposition: C₁₂H₂₂O₁₁ → 12C + 11H₂O. Notice how the H and O atoms leave together as water.
Predict first
What happens to the sugar when it meets the acid?
The acid acts as a powerful dehydrating agent, ripping hydrogen and oxygen out of the sugar molecule as water, leaving behind pure carbon.
- It dissolves to form a sweet black syrup
- It turns into black carbon and releases steam — correct
- It remains white but gets hot
What you do
Add the acid to the sugar. Observe the rapid charring and the formation of the black carbon column.
Check yourself
Why does the sugar turn black?
The reaction is a decomposition where water is removed, leaving solid carbon (char) which is black.
What is the role of concentrated H₂SO₄ in this reaction?
Concentrated sulphuric acid has a strong affinity for water, removing H and O from organic compounds.
Which equation correctly represents this reaction?
The sugar decomposes into carbon and water vapor; no external oxygen is needed for this specific charring process.
- The acid is black and stains the sugar
- Elemental carbon is left behind after dehydration — correct
- The sugar burns due to heat from the acid
- It acts as a dehydrating agent — correct
- It acts as a catalyst that is not consumed
- It provides oxygen for combustion
- C₁₂H₂₂O₁₁ + O₂ → 12CO₂ + 11H₂O
- C₁₂H₂₂O₁₁ → 12C + 11H₂O — correct
- C₁₂H₂₂O₁₁ → 12C + 11H₂ + 11O