Combustion quiz

More questions about Combustion

These visible examples show the question style. LearnClash turns the full topic into ranked duels and spaced repetition.

1. 1 Easy

   What gas does charcoal make instead of CO₂ when air runs short?

   Answer: Carbon monoxide

   Why: Carbon monoxide grips the hemoglobin in blood more than 200 times as tightly as oxygen does, crowding oxygen out.

2. 2 Medium

   Where does the heat of burning methane come from?

   Answer: Forming bonds

   Why: Breaking bonds always takes energy in; burning gives off heat because forming CO₂ and water releases more than that.

3. 3 Hard

   How much CO₂ and water does burning 1 kg of candle wax make?

   Answer: About 4.4 kg

   Why: About 3.1 kg of that is carbon dioxide, roughly three times the wax's own weight, and the other 1.3 kg is water vapor.

4. 4 Easy

   Which fruit's peel sprays oil that flares in a candle flame?

   Answer: Orange

   Why: More than 90% of orange peel oil is limonene, a flammable hydrocarbon that ignites easily as a fine spray.

5. 5 Medium

   Which gemstone burns to nothing but carbon dioxide?

   Answer: Diamond

   Why: Rubies and sapphires are aluminum oxide and quartz is silicon dioxide: already bound to oxygen, they have nothing left to burn.

6. 6 Hard

   Above about what level in air is methane too rich to burn?

   Answer: About 15%

   Why: A mix that is too rich is still dangerous, because air leaking in can dilute it into the burnable range.