Organic chemistry.

Question 1

Crude oil.

Answer 1

Crude oil is
-formed over millions of years from the fossilised remains of plankton (dead animals and plants).
-found in porous rocks in the earth’s crust.
-A finite resource that is used to produce fuels and other chemicals.

Question 2

What is crude oil made up of?

Answer 2

Hydrocarbon (hydrogen and carbon only).

Question 3

What are the properties of a large hydrocarbon?

Answer 3

-More viscous (ie the less easily it flows).
-Higher boiling point.
-Less volatile (does not easily turn into a gas).
-Less easily to ignite.

Question 4

How can crude oil be separated into different fractions?

Answer 4

By fractional distillation.

Question 5

What are the steps of separating crude oil?

Answer 5

1) First the crude oil is heated until it evaporates.
2)The vapour moves up the fractionating column.
3)The top of the column is much colder than the bottom.
4)Shorter hydrocarbon molecules can reach the top of the fractionating column before they condense and are collected.
5)Longer hydrocarbon molecules condense at higher temperatures and are collected lower down the column.

Question 6

Alkanes.

Answer 6

-Carbon atoms are linked to four other atoms by single bonds.
-Alkanes only contain single bonds and are described as saturated hydrocarbons.
-They are fairly unreactive but they burn well.
-They can be drawn with a single line between atoms which represents a single covalent bond.

Question 7

What is the general formula for alkanes?

Answer 7

C nH 2n+2

Question 8

What happens during the combustion of hydrocarbon?

Answer 8

-Bothe carbon and hydorgen are oxidised.
-Energy is released.
-Waste products are produced, which are released into the atmosphere.

Question 9

What is produced in incomplete combustion?

Answer 9

Carbon monoxide and solid particles containing soot (carbon) may be produced.

Question 10

What is cracking?

Answer 10

Longer-chain hydrocarbons being broken down into shorter, more useful hydrocarbons.

Question 11

What happens during thermal cracking?

Answer 11

-The hydrocarbons are heated until they vaporise.
-The vapour is passed over a hot catalyst.
-A thermal decomposition reaction takes place.
-The products include alkanes and alkenes.

Question 12

What happens during steam cracking?

Answer 12

The hydrocarbons are mixed with steam and heated to a high temperature.

Question 13

Why is there a high demand for fuels with small chains?

Answer 13

Because they are easy to ignite and have low boiling points.

Question 14

Alkenes.

Answer 14

They can form single and double bonds.
This means that:
-Not all carbon atoms have to link to 4 other atoms.
-A double carbon-carbon(c=c) bond can be present instead.
-They are unsaturated as they have at least one double bond.

Question 15

What is the general formula for alkenes?

Answer 15

Cn H2n

Question 16

Reactions of alkenes.

Answer 16

-More reactive than alkanes due to the double bond.
-React with oxygen in a combustion reaction.
-Tend to burn with smokier flames than alkanes due to incomplete combustion.
-Hydrogen can be added to alkenes to produce alkanes.
A nickel catalyst is used.
eg: propene + hydrogen = propane
This is an addition reaction.

Question 17

How can ethanol be produced?

Answer 17

It can be produced by reacting ethene with steam in the presence of a catalyst, phosphoric acid.
Ethene + Steam = Ethanol.

Question 18

Bromine water test,

Answer 18

Ethene (colourless) + bromine water (orange-brown) turns colourless when mixed. Alkenes.
Ethane (colourless) + bromine water (orange-brown) stays brown-orange solution. Alkanes.

Question 19

How to draw out an alkane/alkene.

Answer 19

eg propene 1) must be 2 carbons without a hydrogen bond.
2) Add a double bond.
eg propane !) all carbons must have a bond.

Question 20

How can aqueous solutions of ethanol be produced?

Answer 20

By the fermentation of sugar which is a renewable source.

Question 21

What happens during fermentation?

Answer 21

sugar turns into ethanol + carbon dioxide.

Question 22

How does the temperature affect fermentation?

Answer 22

Too low- the yeast becomes inactive and the rate of reaction slows.
Too high- the yeast is denatured and stops working.

Question 23

What are alcohols?

Answer 23

They are carbon-based molecules that contain the functional group hydroxyl, -OH.
Methanol, ethanol, propanol, butanol are the first four members of the homologous (they have the same physical/chemical properties) series of alcohols.

Question 24

Alcohols.

Answer 24

-Dissolve in water to form neutral solutions.
-React with sodium to produce hydrogen.
-Burn in the air to produce carbon dioxide and water.
-Are used as fuels and solvents.

Question 25

What are carboxylic acids?

Answer 25

They are organic compounds that contain the functional group carboxyl, -COOH.

Question 26

Carboxylic acids.

Answer 26

-Dissolve in water to form acidic solutions.
-React with carbonates (eg sodium carbonate) to produce carbon dioxide,
-React with alcohols (in the presence of an acid catalyst) to form esters.
-Do not ionise (dissociate) fully in water so they are called weak acids.

Question 27

Esters.

Answer 27

Alcohols and carboxylic acids react together to form esters.
-Esters contain the functional group COO.
-When ethanol and ethanoic acid react together, the ester formed is ethyl ethanoate.
-They are volatile compounds i.e. they have a low boiling point.
-They have distinctive smells and are used in perfumes and as flavouring in food.

Question 28

Amino acids.

Answer 28

Contain two different functional groups:
-The amine group, NH2
- The carboxyl group, COOH
-Different amino acids join together to form polymers called proteins.

Question 29

DNA.

Answer 29

-It is a very large molecule.
-Stores and transmits the instructions for the development of living organisms and some viruses.
- DNA is made from two polymer chains constructed from 4 different nucleotides: cytosine (c), guanine (G), adenine (A) and thymine (T).
- The two polymer chains form a double helix (spiral).

Question 30

Starch and cellulose.

Answer 30

-Starch and cellulose are polymers made of sugars.
-They are made by plants and are important for life.
-Sugar, starch and cellulose are all carbohydrates.

Question 31

What is addition polymerisation?

Answer 31

When many monomers (small molecules with double bonds) join together to form polymers.

Question 32

What do the properties of polymers depend on?

Answer 32

-What it is made from.
-The conditions under which it was made.
Eg low-density poly(ethene) (LDPE) and high-density poly(ethene) (HDPE) are both made from the same monomers ethene.
However, they have different properties because different catalysts and reaction conditions are used to make them.
LDPE is used to make carrier bags and HDPE is used to make plastic bottles.

Question 33

Thermosoftening polymers.

Answer 33

-Consist of individual polymer chains that are tangled together.
-Have weak intermolecular forces between all pf the polymer chains and soften on heating.

Question 34

Thermosetting polymers.

Answer 34

-Consist of polymer chains that are joined together by cross-links.
-Do not melt when heated.

Question 35

What happens in condensation polymerisation?

Answer 35

Monomer molecules join together to form large polymer molecules and lose small molecules such as water.

Question 36

How are the simplest polymers joint?

Answer 36

They are formed when diols (molecules with two hydroxyls, OH, groups) join together with dicarboxylic acids (molecules with two carboxyl, COOH, groups).

Question 37

Amino acids join together with condensation polymerisation to form?

Answer 37

Polypeptides and water.