Highland Science Department Molecule Shapes Why do these molecules have such different shapes?
We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them...
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Transcript of We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them...
![Page 1: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/1.jpg)
Water
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What about molecules?
• We have been studying about elements just by themselves such as oxygen and hydrogen. • If you put them together you have a
molecule of water (H2O).
• A cup of water contains millions of molecules of H2O.
![Page 3: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/3.jpg)
Chemical Formulas
![Page 4: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/4.jpg)
What is a chemical formula?• Chemical, or molecular, formulas are a concise
way of expressing information about the atoms that constitute a particular chemical compound.
• Wait…what?
• It is an expression which states the number and type of atoms present in a molecule of a substance.
![Page 5: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/5.jpg)
Do you know what the chemical formulas are for the following substances?
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Carbon dioxide
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Sodium chloride or salt
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Magnesium sulfate (AKA Epsom salt)
MgSO4
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For something more complicated….Glucose or sugar
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Subscripts
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Definition• A subscript is used to represent the number of
each atom being represented. • If only one atom is represented, there is no
subscript.• In the formula for water, what is the subscript?• There is only one atom of Oxygen, so it does not
have a subscript.
H2OH2OH = HydrogenO = Oxygen
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Some exceptions exist
• Usually the subscript just multiplies or shows the number of atoms of a single element. If the subscript exists outside of a set of parenthesis then it will multiply the atoms of all of the elements inside the parenthesis.
• How many of each atom are there now?• Answer: Nitrogen-1, Carbon-3, Hydrogen-9
N(CH3)
3
N = NitrogenC = CarbonH = Hydrogen
![Page 13: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/13.jpg)
Here are some molecules…
![Page 14: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/14.jpg)
• In this image the Carbon atom is blue and the Oxygen atom is red.• Write the chemical formula for this
molecule.Answer: CO
This substance is carbon monoxide
![Page 15: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/15.jpg)
• In this image the Carbon atom is black and the Oxygen atoms are red.
• Write the chemical formula for this molecule.
Answer: CO3
This substance is carbonate
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• In this image Hydrogen atoms are white and Nitrogen atom is red.
• Write the chemical formula for this molecule.
Answer: NH3
This substance is ammonia
![Page 17: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/17.jpg)
• In this image blue represents Nitrogen atoms, red represents Oxygen atoms, white represents Hydrogen atoms and black represents Carbon atoms.
• Write the chemical formula for this molecule.
Answer: C8H10N4O2
This substance is caffeine
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Coefficient
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7H2
O
Definition• Coefficients appear on the left side of a chemical
formula.• They are used to multiply all the atoms in a
compound• In the following formula, which is the coefficient?• Earlier we learned that the subscript 2 meant that
there were two Hydrogen atoms. The coefficient 7 means there are 7 times more.
• How many Hydrogen atoms do we have? • How many Oxygen atoms?
7H2
O
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Chemical Equations
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Chemical Equations• representation of chemical reaction in
equation: a representation, using chemical symbols in a form resembling a mathematical equation, of the process involved in a chemical reaction
• This is an example of a chemical equation. The components on the left combine together to yield (represented by the arrow) the component on the right.
2H2+O22H2O
![Page 22: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/22.jpg)
Parts to a chemical equation
![Page 23: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/23.jpg)
•2H2+O22H2O
Reactant Produ
ct
Yields
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Law of conservation of mass
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• Atoms are neither created, nor destroyed, during any chemical reaction.
• This means that the same number of atoms that are present after a reaction are the same number of atoms that are present before a reaction.
• There is only a rearrangement
![Page 26: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/26.jpg)
Balancing chemical equations
![Page 27: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/27.jpg)
Subscripts are never changed when balancing an equation
![Page 28: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/28.jpg)
Step 1• Write out your “un-balanced” equation using
formulas of reactants and products.
CH4+O2CO2+H2O
![Page 29: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/29.jpg)
Step 2• Count up the atoms in the products and reactants.• How many carbons, hydrogens, and oxygens are
on each side? Are they equal?
CH4+O2CO2+H2O
C=1H=4O=2
C=1H=2O=3
They are NOT equal
![Page 30: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/30.jpg)
Step 3• Since our carbons are ok we will not mess with
those now.• However, we have half the number of hydrogens
in the products than we do in the reactants.• What do we need to add? Where do we add it?
CH4+O2CO2+H2OCH4+O2CO2+2H2
O C=1H=4O=2
C=1H=4O=4
They are still NOT equal
![Page 31: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/31.jpg)
Step 4• Now we have half the number of Oxygens.• What do we need to add? Where do we need to
add it? Is everything equal now?
CH4+O2CO2+2H2OCH4+2O2CO2+2H2
O C=1H=4O=4
C=1H=4O=4
They ARE now balanced
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Practice Time
![Page 33: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/33.jpg)
H2+O2H2O2H2+O22H2O
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Fe+Cl2FeCl32Fe+3Cl22FeCl3
![Page 35: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/35.jpg)
Cu+AgNO3Cu(NO3)2+AgCu+2AgNO3Cu(NO3)2+2Ag
![Page 36: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/36.jpg)
Zn+HClZnCl2+H2
Zn+2HClZnCl2+H2
![Page 37: We have been studying about elements just by themselves such as oxygen and hydrogen. If you put them together you have a molecule of water (H 2 O). A.](https://reader036.fdocuments.in/reader036/viewer/2022062423/56649e7b5503460f94b7d294/html5/thumbnails/37.jpg)
Pb(NO3)2+AlCl3PbCl2+Al(NO3)3
3Pb(NO3)2+2AlCl33PbCl2+2Al(NO3)3