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Description
Flashcards by Farha Idrees, updated more than 1 year ago
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Created by Farha Idrees
over 5 years ago
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| Question | Answer |
| What are organic compounds (containing carbon atoms) used for? | fuels to: • run cars • warm homes • generate electricity |
| What are hydrocarbons? | compounds containing only carbon and hydrogen atoms |
| What is crude oil? | a mixture of many different compounds containing carbon atoms - mainly hydrocarbons |
| What's the difference between a mixture and compounds? | Mixtures can be physically taken apart and are two or more elements not chemically bonded together Compounds are chemically bonded elements and to separate them you must break this bond |
| How are crude oils separated? | through fractional distillation, into its different substances before it can be used |
| Why is fractional distillation used? | all the compounds have different boiling points |
| What are fractions? | a group of chemicals with similar boiling points |
| the properties of substances do not change when they are mixed... | as opposed to reacted |
| What is an alkane? (give the general formula) | • a type of hydrocarbon- the most common in crude oil • all the names end in 'ane' • the general formula is Cn H(2n+2) |
| Why are alkanes referred to as 'saturated' hydrocarbons? | all the carbon-carbon bonds are single covalent bonds ↓ this means that they contain as many hydrogen atoms as possible in each molecule ↓ no more hydrogen atoms can be added |
| Name the first four alkanes. | 1. methane, CH4 2. ethane, C2H6 3. propane, C3H8 4. butane, C4H10 |
| The properties of hydrocarbons depend... | ....the size of their molecules |
| Give the properties of short molecules. | • lower boiling points • flammable • higher volatility • low viscosity |
| Give the properties of long molecules. | • high boiling points • not as flammable • lower volatility • high viscosity |
| Define: a) viscosity b) volatility | a) thickness of a solution (how easily it flows) b) tendency to turn into a gas |
| Which type of hydrocarbons are more useful as fuels? | shorter molecules as they ignite more easily and burn well, with a less smoky flame |
| Describe the process of fractional distillation. | 1. crude oil is heated and fed near the bottom of a tall tower, a fractionating column, as hot vapour 2. the column is kept very hot at the bottom and much cooler at the top- the temp decreases going up the column 3. the gases move up the column and hydrocarbons condense when they reach the temperature of their boiling points 4. the different fractions are collected as liquids at different levels 5. the fractions are collected from the column in a continuous process |
| How are the fractions from crude oil used? | • petrol • diesel oil • residue • petroleum gas |
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