EasyChemistryHigh School (9–10)GeneralCarbon and Its Compounds › Reactions and Uses of Carbon CompoundsConceptualBoard Exam
The flame of a gas stove is usually blue…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The flame of a gas stove is usually blue. One day it turns yellow, and the bottom of the pan becomes black. What has gone wrong? What is the black substance? Why is the change dangerous as well as dirty?
Need a reminder? The key ideaShow
Combustion gives carbon dioxide, water, heat and light. Saturated fuels burn with a blue flame; unsaturated ones, or too little air, give a yellow, sooty flame. Oxidising agents turn alcohols into acids. Unsaturated compounds add hydrogen with a nickel catalyst. Saturated ones swap a hydrogen for chlorine in sunlight.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The cause. The air holes of the burner are blocked, so too little oxygen reaches the gas.
Step 2. The black substance. It is soot, carbon that did not burn.
Step 3. The danger. Incomplete burning also makes carbon monoxide, a poisonous gas with no colour or smell. Fuel is wasted too.
Answer: too little air; the black is soot; carbon monoxide may form, which is poisonous.
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