Chemistry paper 2 Flashcards
(34 cards)
What is crude oil?
Crude oil is a naturally occuring product that we use to produce products such as petrol, solvents and detergents.
What is crude oil a mixture of?
It is a mixture of long chain molecules made up of hydrogen and carbon only. These chains are called hydrocarbons.
What is the use of hydrocarbon determined by?
The use of hydrocarbon is determined by the number of carbons in its chain as its properties depend on how long it is.
How can the different lengths of chain molecules be separated?
The different lengths of chain molecules can be separated by fractional distillation.
The different chain lengths of molecules can be separated by using fractional distillation, how does this work?
- The crude oil mixture enters a tall column and is heated to a high temperature to make sure all the molecules are vaporised (turned into gas)
- The column is cooler at the top than the bottom
- As the gaseous molecules rise up the column they condense (turn back into liquid)
- They are then collected and removed
When separating the lengths of chain molecules what are the separate samples called?
Fractions
What do all of the hydrocarbons that are found in crude oil have?
All of the hydrocarbons that are found in crude oil all have single carbon-carbon bonds in their chains. They are said to be saturated and belong to a homologous series called alkanes.
What will incomplete combustion produce?
Incomplete combustion will produce solid carbon (soot), carbon monoxide and unburnt hydrocarbon.
In order to get what we need from crude oil what will we do?
We need to turn long hydrocarbons into short hydrocarbons. This is done with cracking.
What is cracking?
A thermal decomposition reaction
What happens when you crack long hydrocarbons?
When you crack long hydrocarbons, you make short hydrocarbons and an alkene.
What is an alkene
Alkenes are unsaturated hydrocarbons and have a double bond. They can be used to make plastics.
What are the two methods that can be used to crack hydrocarbons?
Catalytic cracking and Steam cracking
What is Catalytic cracking?
The alkene is brought into contact with a powdered aluminium oxide catalyst at moderate pressure and a temperature of around 500 degrees.
What is Steam cracking?
The hydrocarbon is mixed with steam and heated to a very high temperature approximately 850 degrees.
What is cracking an example of?
Thermal decomposition
What do both cracking processes result in?
Both cracking methods result in the formation of two products; an alkane and and alkene.
What are alkenes?
Alkenes are produced as one of the products of cracking. They are also hydrocarbons.
What must the sum of carbon and hydrogen atoms be the same as in the two products of the cracking process?
The sum of the carbon and hydrogen atoms in the two products of the cracking process must be the same as the number of atoms that you started with.
What is the atmosphere made up of?
21% Oxygen
1% Argon
78% Nitrogen
Air also contains 0.04% carbon dioxide and variable amounts of water vapour
Reduction of carbon dioxide by formation of deposites
- Coal
Plants absorbed carbon dioxide. They died and decayed. This layer of decaying plants was compressed to form coal.
Reduction of carbon dioxide by formation of deposites
-Oil and natural gases
Plankton absorbed carbon dioxide. Plankton died and were deposited in muds on the sea floor. They were covered over and compressed over millions of years.
Reduction of carbon dioxide by formation of deposites
- Limestone
Shelled animals absorbed carbon dioxide to make their calcium carbonate shells. The remains of these animals were compressed to make limestone.
Greenhouse Effect and Global Warming
- Greenhouse effect
The process by which the temperature on earth is kept high enough to support life by greenhouse gases absorbing radiation radiated by the earth.
