Carbon cycle (1)

THE CARBON CYCLE
NATTHU SHRIRAME
M-TECH IN ENVIRONMENTAL ENGG

What Is Carbon?
An element: 6 protons, 6 neutrons
The basis of life of earth
Found in all earth systems

Carbon Cycle
 The same carbon atoms are used repeatedly
on earth. They cycle between the atmosphere,
hydrosphere, geosphere and biosphere.

Processes that transfer carbon
 Between earth systems
- Photosynthesis
- Respiration
- Consumption
- Decomposition
- Combustion (Burning)
- Weathering (rocks break down and release carbon)
- Dissolve/Vaporize (Between ocean and atmosphere)

Plants consume and release
Carbon Dioxide
Plants pull carbon from the atmosphere
or hydrosphere and use it to make food
–— photosynthesis.
Plants release carbon by respiration.

Animals consume and release
carbon
When organisms eat (consume) plants
or other organisms, they take in the
carbon and some of it becomes part of
their own bodies.
When they breath (respiration) they
release carbon.

Plants and Animal Die
 When plants and animals die, most of their
bodies are decomposed and carbon atoms are
returned to the atmosphere.
 Some are not decomposed fully and end up in
geosphere deposits underground (soil, oil,
coal, etc.) or at the bottom of ocean.

Natural combustion
 Forest and grass fires are a natural, required
part of the carbon cycle that release carbon
into the atmosphere and geosphere.
 Fire returns carbon to the soil and “cleans out”
unhealthy plants, allowing new plants to grow.

Carbon Slowly Returns to Atmosphere
Carbon in rocks and underground
deposits is released very slowly into the
atmosphere.
This process takes many years and is
usually caused by weathering.

Carbon in Oceans
Oceans store large amounts of carbon.
Largest exchange of carbon in carbon
cycle is the dissolving and vaporization
of carbon dioxide between the
atmosphere and ocean surface.

Carbon Cycle Diagram
Carbon in Atmosphere
Plants use
carbon to make
food
Animals eat
plants and
take in
carbon
Plants and
animals die
Decomposers
break down dead
things, releasing
carbon to
atmosphere and
soil
Bodies not
decomposed —
after many
years, become
part of oil or
coal deposits
Fossil fuels are
burned; carbon
is returned to
atmosphere
(Unbalanced)
Carbon slowly
released from
these substances
returns to
atmosphere

Unbalanced Cycle - Human
Impact
 Under balanced conditions, fossil fuels release
carbon stores very slowly into atmosphere.
 When humans burn fossil fuels, it releases a
tremendous amount of carbon into the
atmosphere over a very short time span.
 Increased carbon dioxide in atmosphere
increases global warming
 Fewer plants mean less CO2 removed from
atmosphere

Things you can do to reduce
your carbon footprint
Promote plant life, especially trees
Buy a fuel efficient vehicle
Purchase locally grown food
Reduce electricity use
Reduce how far/much you drive
Take less airplane trips
Reduce, Reuse, Recycle!

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Organic Chemistry - Introduction
Organic chemistry is the study of
carbon compounds.
Animals, plants, and other forms of life
consist of organic compounds.
Nucleic acids, proteins, fats,
carbohydrates, enzymes, vitamins, and
hormones are all organic compounds.
Biochemistry was developed later as
the study of the chemical compounds
and reactions in living cells.
Intro

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Organic Chemistry - Introduction
 Scientists had originally thought that organic
compounds contained a “vital force” due to
their natural origin.
 This was disproved by Friedrich Wöhler in 1828.
 Wöhler was able to make urea, a carbon
compound in human urine, in the laboratory
from a mineral.
 Organic chemistry is an enormous field.
Intro

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Bonding in Organic Compounds
 Besides carbon, the most common elements
in organic compounds are hydrogen, oxygen,
nitrogen, sulfur, and the halogens.
 All of the preceding elements are non-metals,
therefore organic compounds have covalent
bonding.
 Any structural formula that obeys the bonding
rules in the following table probably
represents a possible compound.
 A drawn structure that breaks the bonding rules is
unlikely to exist.
Section 14.1

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Numbers and Types of Bonds
Application of the octet rule indicates that these elements should bond as shown below:
Section 14.1

properties
 Organic compounds are usually combustible.
 Organic compounds, in general, have lower melting
and boiling points.
 Organic compounds are usually less soluble in water.
 Several organic compounds may exist for a given
formula. This is known as isomerism.
 Most organic compounds can serve as a source of
food for bacteria.
 Reactions of organic compounds are usually
molecular rather than ionic. As a result, they are often
quite slow.

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Classification of Hydrocarbons
Section 14.2

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Aromatic Hydrocarbons
Aromatic hydrocarbons contain one or
more benzene ring.
Benzene (C6H6) is the most important
aromatic hydrocarbon.
It is a clear, colorless liquid with a
distinct odor, and is a carcinogen
(cancer-causing agent.)
Traditional Lewis Structure
Section 14.2

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Benzene
Structural Formulas and Short-hand Symbols
 The Lewis structure and the Kekulé symbol both
indicate that the carbons in the ring have alternating
double and single bonds.
Section 14.2

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Aliphatic Hydrocarbons
Aliphatic hydrocarbons are
hydrocarbons having no benzene rings.
Aliphatic hydrocarbons can be divided
into four major divisions:
Alkanes
Cycloalkanes
Alkenes
Alkynes
Section 14.3

hydrocarbon
 Saturated hydrocarbons are those in which
adjacent carbon atoms are joined by a single
covalent bond and all other bonds are satisﬁed
by hydrogen.
 Unsaturated hydrocarbons have at least two
carbon atoms that are joined by more than one
covalent bond and all remaining bonds are
satisﬁed by hydrogen.

14 | 26
Alkanes
 Alkanes are hydrocarbons that contain only
single bonds.
 Alkanes are said to be saturated hydrocarbons
 Because their hydrogen content is at a maximum.
 Alkane general formula  CnH2n + 2
 The names of alkanes all end in “-ane.”
Section 14.3

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The First Eight Members of the
Alkane Series
All satisfy the general formula CnH2n + 2
Section 14.3

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Visualization of an Alkane’s Structure
Section 14.3
Structural formula – a graphical
representation of the way atoms
are connected
Condensed structural formula –
save time/space and are
convenient
Ball-and-Stick models – 3D
models that can be built by
students

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Alkyl Group
Alkyl group contains one less hydrogen
than the corresponding alkane.
In naming this group the “-ane” is
dropped and “-yl” is added.
For example, methane becomes methyl.
Ethane becomes ethyl.
Section 14.3

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Alkyl Group
This group does not exist independently but occurs
bonded to another atom or molecule.
Section 14.3

14 | 31
Alkenes
 Members of the alkene group have a double
bond between two carbon atoms.
 One hydrogen atom has been removed from
two adjacent carbon atoms, thereby allowing
the two adjacent carbon atoms to form a
double bond.
 General formula is CnH2n
 Begins with ethene (ethylene)
 C2H4
Section 14.3

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Some Members of the Alkene
Series
Section 14.3

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Naming Alkenes
 “-ane” suffix for the corresponding alkane is
changed to “-ene” for alkenes.
 A number preceding the name indicates the
C atom on which the double bond starts.
 The carbons are numbered such that the double
bond has the lowest number.
 For example, 1-butene and 2-butene
Section 14.3

Carbon cycle (1)

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