<< Chapter < Page Chapter >> Page >

The hydrocarbons

Let us first look at a group of organic compounds known as the hydrocarbons . These molecules only contain carbon and hydrogen. The hydrocarbons that we are going to look at are called aliphatic compounds . The aliphatic compounds are divided into acyclic compounds (chain structures) and cyclic compounds (ring structures). The chain structures are further divided into structures that contain only single bonds ( alkanes ), those that contain at least one double bond ( alkenes ) and those that contain at least one triple bond ( alkynes ). Cyclic compounds include structures such as the benzene ring . [link] summarises the classification of the hydrocarbons.

The classification of the aliphatic hydrocarbons

Hydrocarbons that contain only single bonds are called saturated hydrocarbons because each carbon atom is bonded to as many hydrogen atoms as possible. [link] shows a molecule of ethane which is a saturated hydrocarbon.

A saturated hydrocarbon

Hydrocarbons that contain double or triple bonds are called unsaturated hydrocarbons because they don't contain as many hydrogen atoms as possible. [link] shows a molecule of ethene which is an unsaturated hydrocarbon. If you compare the number of carbon and hydrogen atoms in a molecule of ethane and a molecule of ethene, you will see that the number of hydrogen atoms in ethene is less than the number of hydrogen atoms in ethane despite the fact that they both contain two carbon atoms. In order for an unsaturated compound to become saturated, a double bond has to be broken, and another two hydrogen atoms added for each double bond that is replaced by a single bond.

An unsaturated hydrocarbon

Interesting fact

Fat that occurs naturally in living matter such as animals and plants is used as food for human consumption and contains varying proportions of saturated and unsaturated fat. Foods that contain a high proportion of saturated fat are butter, ghee, suet, tallow, lard, coconut oil, cottonseed oil, and palm kernel oil, dairy products (especially cream and cheese), meat, and some prepared foods. Diets high in saturated fat are correlated with an increased incidence of atherosclerosis and coronary heart disease according to a number of studies. Vegetable oils contain unsaturated fats and can be hardened to form margarine by adding hydrogen on to some of the carbon=carbon double bonds using a nickel catalyst. The process is called hydrogenation

We will now go on to look at each of the hydrocarbon groups in more detail. These groups are the alkanes, the alkenes and the alkynes.

The alkanes

The alkanes are hydrocarbons that only contain single covalent bonds between their carbon atoms. This means that they are saturated compounds and are quite unreactive. The simplest alkane has only one carbon atom and is called methane . This molecule is shown in [link] .

The structural (a) and molecular formula (b) for methane

The second alkane in the series has two carbon atoms and is called ethane . This is shown in [link] .

The structural (a) and molecular formula (b) for ethane

The third alkane in the series has three carbon atoms and is called propane ( [link] ).

Questions & Answers

how does cell look like
Charu Reply
What is impulse and how does it = to momentum
Robin Reply
what is physics
Jhon Reply
what is a catanation ?
Rithabele Reply
The ability of a few elements, most especially carbon, to yield chains and rings by forming covalent bonds with atoms of the same element.
Ofentse
different structural formula
Lucas Reply
different type of structural formula
Lucas
primary,secondary and tertiary
Snowy
how does the earth revolute
Kevin Reply
What is the momentum
Given Reply
The product of the object's mass and it's velocity
Mvula
electric field def
FREENCO
what is secondary alcohol?
Raymond
is when Carbon that is bonded with OH is also bonded to 2 carbons of the chain.
Gontse
Electric field is the region of space around a charged object where other charged objects will experience an electrostatic force ( coulomb forces) without coming into contact with the object that is generating the field.
Kagiso
Electric field is the region of space around a charged object where other charged objects will experience an electrostatic force ( coulomb forces) without coming into contact with the object that is generating the field.
Kagiso
how is ester formed
Aubrey Reply
how is n ester formed
Aubrey
Alcohol reacts with a carboxylic acid
Texas
and the reaction is catalysed by sulphuric acid
Vhulenda
An ester is form when an alcohol reacts a carboxylic acid and sulphuric acid is used as a catalyst which therefore eliminates water.
Azola
an athlete with a mass of 70kg runs at a velocity of 45km . determine the athlete's momentum
Lesedi Reply
Is that a velocity or something else
msawenkosi
45km/h i guess
Texas
Change to m/s
Texas
45km/h = 12.5 m/s p=mv =70×12.5 =875 kg.m/s
Thato
what are the measures of the rates of reaction
Lesego Reply
Volume Concentration Temperature Pressure Surface Area
Thato
the principle of superposition of waves
Sfundo Reply
what is work
Kool Reply
is this a group chat
Nobuhle Reply
Hey can y'all define newton's 2nd law
mthebzification
If a resultant force act on an object...the object will accelerate in the direction of a resultant force,the acceleration of the object is directly proportional to the net force and inversely proportional to the mass of the object
mosa
how do you calculate tension force
Bulumko
use the formula Fnet=ma if there is tension connecting two objects
Sboniso
to calculate Tension, usually calculate acceleration first Draw separate free body diagrams for each body. Apply Fnet = ma to calculate Tension
Kevin
Hi people
Paul
when a resultant force acting on an object the object will accelerate in the direction of a force at an acceleration directly proportional to the force and invesly proportional to the mass of the object.
Raymond
Hey people
Kaytee
how does temperature affect the equilibrium position
Blessing Reply
an increased temperature increases the average kinetic energy thus in turn increases the number of effective collisions........
Lwando
so...which reaction is favored between endothermic and exothermic .when temperature is increased..?
Blessing
exothermic reaction because energy is realised to the surroundings as heat and light energy ....graphical so much energy is realised as reactants to form product and because temperature is high rate of reaction is fast which means there is a successful collision
Code
INTEMENDO - INCREASE IN TEMPERATURE FAVOURS ENDOTHERMIC DETEMEXO - DECREASE IN TEMPERATURE FAVOURS EXOTHERMIC
Thato
an object will continue in a state of rest unless it is acted upon an unbalanced force
Junior Reply
Newton's Law 1
Code
First Newton's Law
Azola
Newton's first law
Surprise
newton first law
Thinavhuyo
Newton's first law
Blessing

Get the best Siyavula textbooks: gr... course in your pocket!





Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 12 physical science' conversation and receive update notifications?

Ask