Molecule unit

1. Molecules
Presented by Kesler Science

2. Essential Questions:
1. What are the basic differences of
elements, molecules, and compounds?
2. What determines the number of
molecules in a chemical equation?

3. Lets Review –
• The basic building blocks for all
matter is an atom.
• An element is a substance
consisting of a single type of atom.
Molecules
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4. Molecules
• The smallest fundamental unit
of a chemical compound
• Made up of two or more atoms
bonded together
• The atoms can be the same or
different.
Molecules
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Examples of molecules
•O2 – oxygen
•O3 - ozone
•H2O – water
•CO2 - carbon dioxide
•H2SO4 – sulfuric acid

5. Molecules
• Formed when two or more atoms
bond together chemically
• Bonds can form between same
atoms or different atoms.
• These bonds form as a result of the
sharing or exchange of valence
electrons among atoms.
Molecules
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Oxygen atoms
Oxygen molecule
O2
Valence electrons are
always looking to fill the
outer most electron layer.
By sharing electrons both
oxygen atoms now have
complete outer shells.
6 valence electrons in
an oxygen atom
Needs 2 electrons to
have a full outer shell
Two oxygen atoms bonding by sharing electrons

6. Elements
• The most basic form of a
material.
• One or more atoms of the
same type.
• Elements are listed on the
periodic table.
Molecules
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Examples of elements
•O – oxygen
•H - hydrogen
Elements that naturally
exist as molecules
•O2 – oxygen
•O3 - ozone

7. Compound
• A chemical substance formed when
two or more different elements
bond in a specific proportion.
• The elements lose their individual
chemical properties and the
compound has new properties.
Molecules
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Poisonous gasExplosive solid

8. Compound
• Chemical bonds are a result of the
sharing or exchanging electrons
among the atoms.
• A molecule is the smallest unit
that still keeps the properties of
the compound.
• If the compound could be broken
any further, the parts would be
elements with different properties.
Molecules
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Water Molecule2 Hydrogen atoms
1 Oxygen atom
Properties:
both are gases
neither conducts
electricity
Properties:
liquid
conducts electricity

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Quick INB Action – Molecules Practice
Molecules
Compounds
Elements
1. Quickly sketch the 3 circles
2. Draw each object in the correct circle.

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Quick Action – Molecules Practice
Grab a partner and let’s practice. Is it an element, molecule, compound, or combination?
Formula Molecule Compound Element Both Compound
and Molecule
Both Element
and Molecule
O2
NaCl
CH4
H2
H
Write a rule that you can follow for determining the difference in a compound and a molecule.
Here is a hint… All ___________ can be ___________, but…..

11. © KeslerScience.com
Quick Action – Molecules Practice
Grab a partner and let’s practice. Is it an element, molecule, compound, or combination?
Formula Molecule Compound Element Both Compound
and Molecule
Both Element
and Molecule
O2
NaCl
CH4
H2
H

12. Chemical Formula
• The recipe for a chemical
substance
• Tells the number of atoms of each
element in a compound or
molecule
• Uses symbols for the elements
present and subscripts (small
numbers) to indicate the number of
elements
• Ex. H2O - water
Molecules
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subscript
2 Hydrogen atoms and 1 oxygen atom
H2O
H +H + O
H H
O

13. Chemical Equation
• A shorthand that scientists use to
describe a chemical reaction
• The number in front of
the element symbol (called a
coefficient) indicates the number
of molecules.
• If no coefficient appears in front
of a molecule, we interpret this
as meaning one.
Molecules
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2H2 + O2 → 2H2O
2 hydrogen molecules +
1 oxygen molecules =
2 water molecules
Coefficient

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Quick Action – Molecules Practice
Grab a partner and let’s practice. Count the molecules in each
balanced equation.
1. CH4 + 2O2 CO2 + 2H20 _____ CH4 _______ O2 _______ CO2
_________H20
2. 2Fe +3Cl2 2FeCl3 _____ Fe _____ Cl2 _____ FeCl3
3. P4O10 + H2O 4H3PO4 _____ P4O10 ______ H2O _____ H3PO4
1
1 1
12
2 2
2
3
4

15. Check for Understanding
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Can You-
• Describe the differences in an
element, a molecule, and a
compound?
• Determine the number of molecules
in a balanced equation?