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02 Nelson Science for WA Yr 10 TXT 5pp.indd 40
e.g. steel
e.g. Mg
e.g. CaCO3
Inorganic
compounds
Small
molecules
e.g. H2O
e.g. silica
(sand)
Inorganic
compounds
e.g. silicone
rubber
Giant
molecules
(polymers)
Organic
compounds
COMPOUNDS
(NON-IONIC)
Giant
covalent
lattices
e.g. CH3MgBr
Organo-metallic
compounds
Figure 2.4 The major classes of substances in our world
Note: Some alloys contain
non-metal atoms
in their structure.
Alloy
(mixture of
elements)
IONIC
COMPOUNDS
NON-METALS
e.g. CH4
Small
molecules
e.g. proteins
Giant
molecules
(polymers)
ELEMENTS
Noble gases
Separate
atoms
Pure
element
e.g. O2
Small
molecules
See note about
alloys.
e.g. diamond
Giant
covalent
lattices
Figure 2.4 is a chart that shows the major
classes of chemicals known today. Within
each class, there are many, many families.
Only some examples are shown.
Pure element
(giant lattice)
ELEMENTS
METALS
Science for WA 10
02 The chemical world
The major classes of chemical
substances
13/01/10 12:17 PM
Science for WA 10
02 The chemical world
Organic and inorganic compounds
>>Alchemists once
thought that the golden
colour of urine meant it
might contain gold, or
the mythical substance
that would turn base
metals into gold – the
philosopher’s stone.
Many therefore spent
a great deal of time
experimenting with
urine. Of course they
did not succeed,
because urine does
not contain gold or any
substance that will turn
other metals into gold.
However, their research
led to some interesting
discoveries.
White phosphorus
was discovered by
the German alchemist
Hennig Brandt in
1669 when he heated
fermented urine to a
very high temperature.
Much to his great
surprise, he produced
a waxy white substance
that glowed in the dark!
This new element was
named from the Greek
word phosphoros,
meaning ‘bringer of
light’.
Just over 100 years
later, in 1773, the
French chemist Hilaire
Rouelle boiled some
urine dry. He noticed
that white crystals
were produced. This
was the first time that
urea was isolated.
Before the 1800s, chemists were aware of some of the elements, although it was not always
clear whether a newly discovered substance was an element or a compound. The noble gases
were not yet known. At that time, compounds were classified as either organic compounds
or non-organic compounds, which were described as inorganic compounds.
The term organic came about because it was once believed that only living organisms
could make these compounds. In fact, it was suggested that organic compounds had different
properties from inorganic compounds because they contained the ‘vital force of life’.
However, the humble urea molecule present in our urine proved this was not the case. In 1828,
the German chemist Friedrich Wöhler accidentally synthesised (built up, or manufactured)
urea in his laboratory, when trying to make an ionic compound called ammonium cyanate.
Urea has the chemical formula (NH2)2CO. Since that discovery, thousands of organic
substances have been synthesised, including pharmaceuticals and plastics.
Today, chemical compounds are still classified as organic or inorganic. Of course, by
‘organic’, chemists do not mean ‘free of pesticides and herbicides’! Organic compounds are
defined as compounds of carbon. Hydrogen is always present in these compounds as well.
Other elements may also be present (Figure 2.2).
Some compounds of carbon and hydrogen, however, are classified as inorganic. An example
of this is sodium hydrogen carbonate (commonly known as bicarbonate of soda), NaHCO3.
Amazingly, there are literally millions of organic compounds. There are at least 10 times as
many organic compounds as inorganic compounds, and more are being discovered every day.
The study of inorganic chemicals and organic chemicals, known as inorganic chemistry and
organic chemistry, are considered two of the major fundamental branches of chemistry today.
The other major branch is known as physical chemistry.
Inorganic
BLM 2.1 The molecules
quiz
Nitrogen
Carbon dioxide
Ammonia
Organic
n-pentane
A typical fat molecule
Figure 2.2 Models of some organic and inorganic molecules
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ISBN 9780170181518
BLM 2.2 More simple
molecules
Figure 2.3 An organic chemist at work
Exercise 01
Answer the following questions in your journal.
Questions 1–4 are all multiple-choice questions. Select the one correct or best answer.
1 Which one of the following statements about organic compounds is true?
A Organic compounds can only be produced by living organisms.
B All organic compounds contain carbon and hydrogen.
C All compounds containing carbon and hydrogen are classified as organic compounds.
D Organic compounds are compounds that occur in nature.
2 About how many organic compounds are known to exist?
A Hundreds
B Thousands
C Tens of thousands
D Millions
3 Which one of the following compounds would be classified as organic?
A Propane, produced when plants and animals decompose in the absence of oxygen, C3H8
B Carbon monoxide, produced when coal and wood burn in a limited oxygen supply, CO
C Water, produced during the breakdown of proteins and fats and oils in the body, H2O
D Calcium hydrogen carbonate, produced when water trickles through limestone, Ca(HCO3)2
>>Strangely, although
they certainly are
banned from being
sprayed onto organic
foods, almost all
pesticides and
herbicides are in fact
organic compounds.
On the other hand,
living organisms
can make inorganic
compounds. For
example, oysters
manufacture pearls and
shells, both of which
are made from the
inorganic compound
calcium carbonate.
4 What is the first organic compound that was synthesised in a laboratory?
A Carbon dioxide
B Alcohol
C Urea
D Nylon
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