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#1 2007-06-17 00:05:16

Laterally Speaking
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Registered: 2007-05-21
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Chemicals

For those who don't know anything about the subject, I'll start pretty basically: all matter in the universe is composed of molecules, which are, in turn, composed of atoms, which are composed of electrons and nuclei (protons, neutrons).

A chemical compound is a molecule. DNA is one of the largest types of molecules known to humans, but there are undoubtedly even larger ones somewhere out there.

There are about 200 known elements, or types of atoms, each with a different number of electrons and protons. quite a few of these have isotopes. Each isotope corresponds to a certain number of neutrons in the nucleus, and they each have slightly different characteristics.

The chemical symbols for each of the know elements can be looked up in a periodic table. A chemical compound is usually denoted in the following way: take the symbol for one of the elements in the compound, followed by the number of atoms of that element present in one molecule of the compound, followed by the same thing for each of the other elements present.

Here are a few relatively common compounds:
O2: Oxygen gas, necessary for life.
H2O: Water, necessary for life.
O3: Ozone, highly unstable at room temperature, provides shielding against UV light.
N2: Nitrogen gas, the most present gas in Earth's atmosphere.
CO2: Carbon dioxide, present in the atmosphere, byproduct of the breathing process of all living things, as well as the burning of hydrocarbons.
CH4: Methane, lightest hydrocarbon, decays rapidly in oxygen.
Cl2: Chlorine, poisonous to most forms of life, used to "purify" water in pools.
F2: Fluorine, also poisonous to most forms of life, used in toothpaste.
HCl: Hydrochloric acid, main constituent of stomach acid, relatively powerful.


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#2 2007-06-17 00:18:51

Laterally Speaking
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Registered: 2007-05-21
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Re: Chemicals


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#3 2007-06-17 01:21:07

JaneFairfax
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Registered: 2007-02-23
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Re: Chemicals

A chemical compound is a molecule.

Not all of them are. A chemical compound consists of atoms of two or more elements chemically bonded together. Some of them (e.g. carbon dioxide CO[sub]2[/sub]) are molecules, but some others (e.g. sodium chloride NaCl) consists of atoms that are ionically bonded with each other and do not really form molecules.

On a similar note, not all molecules are compounds either. Diatomic oxygen O[sub]2[/sub], for instance, is an element, not a compound. (A compound must contain at least two elements.)


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#4 2007-06-17 02:31:08

Identity
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Registered: 2007-04-18
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Re: Chemicals

There is something my science teacher told the class way back in 8th grade when I was half paying attention, he said something about how water should in fact be

, not
... anyway, why is that??

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#5 2007-06-17 02:56:39

JaneFairfax
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Re: Chemicals

Water is H[sub]2[/sub]O. H[sub]2[/sub]O[sub]2[/sub] is hydrogen peroxide. That’s a bleaching agent, a different compound from water. neutral


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#6 2007-06-17 06:12:18

Laterally Speaking
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Re: Chemicals

2H2O2 is two molecules of hydrogen peroxide. Another thing about H2O2 is that it decomposes into O2 and H2O. This is written as: 2H2O2-->O2 + 2H2O.
By the way, O2 is not an element; it's just the natural, and most stable, form of oxygen. It is the only molecule that contains only oxygen that is stable.


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#7 2007-06-17 06:19:50

luca-deltodesco
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Registered: 2006-05-05
Posts: 1,470

Re: Chemicals

actually, it only partially decomposes, its an unstable molecule, it should be written like this:

the percentage of hydrogen peroxide in any sample of water depends upon its temperature, pressure etc.

Last edited by luca-deltodesco (2007-06-17 06:20:19)


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#8 2007-06-17 06:23:55

Laterally Speaking
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Re: Chemicals

I was going to explain the naming process for hydrocarbons, but realized that it's pretty complicated, being that I learned it my Organic Chemistry book.

To give you the bases, a hydrocarbon chain with only single bonds between the carbons is an alkane. Alkanes are name as follows: take the Greek number of carbon atoms in the string, followed by the suffix ane
If the molecule has one or more double bonds between carbons, then it is an alkene. You name the alkenes in the following manner: number the carbons starting from both ends. Use the number set for which the first atom of a double bond has the lower number. Now there are two ways to proceed: you can either write the Greek number of carbons, followed by a hyphen, the number that corresponds to the first atom of the first double bond, another hyphen, and the ene. The other method is slightly different; you put the number of the first atom, then the Greek number, then the suffix.
If the molecule has one or more triple bonds between the carbons,it is an alkyne. Proceed as above, using the suffix yne.

Last edited by Laterally Speaking (2007-06-17 06:24:24)


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#9 2007-06-17 06:32:13

luca-deltodesco
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Registered: 2006-05-05
Posts: 1,470

Re: Chemicals

An Alkane has the general formula :

where n is the number of carbon atoms
An Alkene has the general formula :
where n is the number of carbon atoms

alkenes can be tested for by mixing with bromine, if alkenes are present, the bromine will react accross the double bond and go colourless:

H   H   H                            H   H   H
|    |    |                             |    |   |
C=C--C--H + Br--Br   ->H--C--C--C--H
|         |                              |    |   |
H        H                             Br  Br  H

Alkenes also undergo addition reactions to form alkanes, used in the production of polymers, for example:

i would draw a diagram, but it takes too long tongue

An alcohol has the general formula:

where n is the number of carbon atoms.

Last edited by luca-deltodesco (2007-06-17 06:33:16)


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#10 2007-06-17 11:34:40

JaneFairfax
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Registered: 2007-02-23
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Re: Chemicals

Laterally Speaking wrote:

By the way, O2 is not an element

Yes, it is! smile

And alkynes, by the way, have the general formula C[sub]n[/sub]H[sub]2n−2[/sub]
­


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#11 2007-06-17 17:40:01

Laterally Speaking
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Registered: 2007-05-21
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Re: Chemicals

Then what is ozone?

About ozone: if you put some into a test tube, when it reaches room temperature, it will turn into O2 so violently that the test tube doesn't shatter, it just turn into a pile of glass dust.


"Knowledge is directly proportional to the amount of equipment ruined."
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#12 2007-06-17 21:59:04

JaneFairfax
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Registered: 2007-02-23
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Re: Chemicals

Both “dioxygen” O[sub]2[/sub] and ozone O[sub]3[/sub] are different forms of the element oxygen. They are (to use the technical term) allotropes of the element oxygen.


Q: Who wrote the novels Mrs Dalloway and To the Lighthouse?

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#13 2007-06-18 03:50:51

Laterally Speaking
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Registered: 2007-05-21
Posts: 356

Re: Chemicals

Right. Sorry if my knowledge of the subject is a little spotty, I learned what I know on my own; the chemistry class at school is REALLY basic (no pun intended).

On the subject of bases and acids, does anyone here (besides me) know what the strongest acid and the strongest base know are?


"Knowledge is directly proportional to the amount of equipment ruined."
"This woman painted a picture of me; she was clearly a psychopath"

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