Chemistry unit 7 Flashcards
What is crude oil and how is it formed
a recourse found in the earth made from ancient biomass that has been underground for a long time. It is a mixture of lots of different compounds, all mostly hydrocarbons
What is a hydrocarbon
A substance made up of only hydrogen and carbon
What is a mixture
2 or more elements not chemically bonded together but physically together. the elements still have their individual properties
How do we separate substances in a mixture
via distillation methods like fractional distillation
What is an alkane
A saturated hydrocarbon with carbon-carbon single bonds
What does it mean if a substance is saturated
carbon-carbon single bonds
What is a homologous series
A group of compounds which share similar formulas, have the same functional group and have similar chemical properties. e.g. Alkane
What is a functional group
The atoms in a substance that determine which homologous series it is in
general formula for alkanes
CnH2n+2
name the first 4 alkanes
methane, ethane, propane, butane
How many bonds does each carbon have?
4
Describe the process of fractional distillation
-Crude oil is heated to very high temperatures in the fractioning column and it is vapourised so the crude oil is a gas
-Each fraction of hydrocarbon has a different boiling point so they will condense at different levels in the fractional column so they are separated and can then be tapped off for use.
-The largest hydrocarbons form at the bottom and the smallest form at the top of the column
What is the use of this industrial fractional distillation of hydrocarbons
-we use many of the fractions that we get off like kerosene or gasoline for fuels
-we get other products that are useful in the petrochemical industry as solvents or polymers
What is a fuel
A recourse that when burned, produces heat energy
How does the sizes of hydrocarbons affect their properties
-The larger the hydrocarbon, the higher the boiling point
-The larger the hydrocarbon is, the less flammable it is
-The larger the hydrocarbon is, the dirtier the flame produced is
-The larger the hydrocarbon is, the more viscous it is
What are the products when we burn hydrocarbons
Carbon dioxide + water (complete combustion with sufficient oxygen)
Carbon (Monoxide) + water (incomplete combustion with not enough oxygen present)
What properties should a good fuel have
-Clean flame to burn
-high flammability
-low boiling point
How do we test to see whether combustion has taken place from a hydrocarbon
When the heat is put through the funnel and down the tubes, the ice bath will condense the water vapour and we can confirm its Prescence by hydrating anhydrous copper sulphate.
We put limewater at the end of the tube so that when the CO2 reaches it, it will turn cloudy.
we have proved the Prescence of Water and CO2 so complete combustion has taken place.
What is the process of cracking ? Why do we do it
When we break up larger alkanes into a smaller alkane and an alkene. There is a greater demand for small chain alkanes and alkenes can be used to make polymers.
What can we use long chain alkanes for
Road tar like bitamine
What is an alkene
An unsaturated hydrocarbon with 1Carbon=Carbon Double bond
What conditions and process done in order to carry out cracking
-The hydrocarbon is vapourised at around 800’C and passed over a zeolite catalyst (catalytic cracking)
-Or we can mix the hydrocarbon with steam at very high temperatures so thermal decomposition happens (steam cracking)
general formula for alkenes
CnH2n