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SingaporeCombined ScienceQuick questions
Chemistry: Metals and Organic Chemistry
Quick questions on Organic chemistry, fuels and alkanes: N(A)-Level Combined Science Chemistry
3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is crude oil?Show answer
Crude oil is a mixture of many different hydrocarbons formed underground over millions of years. Because it is a mixture, it is separated by fractional distillation: the oil is heated and the different hydrocarbons boil off and are collected at different temperatures as fractions. Useful fractions include petrol, diesel, kerosene (jet fuel) and bottled gas. Each fraction has its own uses.
What is complete combustion?Show answer
When a hydrocarbon burns in plenty of oxygen, it undergoes complete combustion, giving carbon dioxide and water:
What is incomplete combustion?Show answer
When there is not enough oxygen, incomplete combustion happens. It releases less energy and produces carbon monoxide (a toxic gas) and carbon (soot) as well as water. This is why a poorly ventilated flame is dangerous and sooty.
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