Reactions of carbon compounds

Combustion: carbon compounds burn in oxygen to give carbon dioxide and water, with heat and light. That is why they make good fuels.

CH₄ + 2O₂ → CO₂ + 2H₂O

Look at the flame. Saturated hydrocarbons usually burn with a clean blue flame. Unsaturated ones give a yellow, smoky flame with black soot. Even a saturated fuel gives a sooty flame when there isn't enough air. So if the bottoms of the pots at home turn black, the stove's air holes are blocked.

Coal or charcoal in an angithi often just glows red without a flame. A flame appears only when gases burn. Wood burns with a flame at first because the substances that turn to gas burn first.

Oxidation: substances called oxidising agents, such as alkaline potassium permanganate, add oxygen. They turn ethanol into ethanoic acid. The purple colour of the permanganate disappears as it is used up.

Addition: unsaturated hydrocarbons add hydrogen across their double bond, with nickel as a catalyst. This hydrogenation turns liquid vegetable oils into solid fats like vanaspati ghee. But note the book's health point: animal fats and saturated fats are said to be harmful, so oils with unsaturated fatty acids are the better choice for cooking.

Substitution: saturated hydrocarbons are fairly unreactive. But in sunlight, chlorine takes the place of hydrogen atoms one by one, like a substitute player coming on in place of another:

CH₄ + Cl₂ → CH₃Cl + HCl