The document discusses the basic concepts of elements, compounds, atoms, molecules, and chemical reactions. It explains that elements are made of only one type of atom, while compounds are made of two or more elements chemically bonded together. Atoms can bond by sharing or transferring electrons to form molecules or ionic compounds with new properties. A chemical reaction occurs when bonds in reactants are broken and new bonds form, creating different products while conserving mass. Energy is either absorbed or released in chemical reactions.

1. Elements and Compounds
Notes 1/20/10

2. Atoms are the smallest parts of
Elements
Everything that exists is made up of different combinations of elements.
All of the elements that are known are listed by their properties on the periodic table.
The smallest little piece of any element that you can have is called an ATOM.
Metals on the left, nonmetals on the right, similar properties

3. All atoms of an
element have the
same # of protons
The # of protons in the atoms of a substance is what makes it different and unique.
That is why it is used as the atomic number to identify an element on the periodic table.
Ex: The only difference between Fluorine and Neon is 1 proton.

4. Atoms like to share
electrons
This takes energy
This bonds them
together
This creates a new
substance called a
molecule
Some atoms like to pair up with other atoms. Some atoms do this easily (like Na) and others
don’t (C). This depends on their reactivity. Other atoms don’t do it at all (noble gases).
When they pair up, it has to do with giving each other electrons. When they do that, it
creates a CHEMICAL BOND that makes them stick together.

5. You cannot separate atoms that have been bonded together by physical means (like
separating a mixture). In order to separate atoms, or bond them together, or make them
rearrange, they have to go through a chemical reaction.
It takes energy, sometimes a lot of it, to separate atoms that are sharing electrons.

6. +
Sodium Chlorine Sodium Chloride
(Na) (Cl) (NaCl)
New Substance = New Properties
A chemical reaction is when a chemical change takes place and there are new chemical bonds
formed. When this happens, the new compound has totally different physical and chemical
properties, because it has been changed (that’s why a change in properties indicates a
chemical change).

7. +
Sodium Chloride
Sodium Atoms Chlorine Atoms
Molecules
A chemical reaction is when a chemical change takes place and there are new chemical bonds
formed. When this happens, the new compound has totally different physical and chemical
properties, because it has been changed (that’s why a change in properties indicates a
chemical change).

8. Molecules are the smallest parts of
COMPOUNDS

9. Gold
Au
Pure
Substances
Elements OR
compounds have Sugar
only one type of C6H12O6
component

10. That’s what makes them
PURE SUBSTANCES
Has only one type of component (atom)
Mixture Pure Substance

11. Chemical Reactions...
Reactants
Yields
Products
This is an example of how a chemical reaction works. Imagine each person is a type of atom.
They break up with whatever partner they are bonded with and reorganize with new partners.
Are there the same total number of people (atoms) at the beginning and the end? YES They
have just changed places. This is how the conservation of mass is. You aren’t destroying
anything during a chemical reaction, you are just changing the properties of the substances
by arranging the atoms differently.

12. Chemical Reactions...
ENERGY
ADDED
ENERGY
RELEASE
Start with End with
3 total people 3 total people
(3 atoms) (3 atoms)
This is an example of how a chemical reaction (change) works. Imagine each person is a type
of atom. They break up with whatever partner they are bonded with and reorganize with new
partners. Are there the same total # of people (atoms) at the beginning and at the end? YES
They have just changed places. This is how the conservation of mass is. You aren’t
destroying anything during a chemical reaction, you are just changing the properties of the
substances by arranging the atoms differently.

13. Chemical Reactions...
ENERGY
ADDED
ENERGY
RELEASE
It takes energy to start a chemical reaction, because it requires energy to break bonds (you
are doing work on the bonds).
When the bonds reform to make new substances, it releases chemical energy stored in the
compounds.
If it absorbs more energy than it releases, the temperature drops because it is using more
energy than it is releasing (endothermic)
If breaking the bonds doesn’t require much energy, but it releases more, then the
temperature raises (exothermic)

14. Think back...
How does what we have talked about relate to
the chemical reaction you researched?

15. Vinegar + Baking Soda
What elements make up the molecules of vinegar and
baking soda?
How were the water, carbon dioxide, and sodium
acetate made?
How many reactants and products did you have?
Was this reaction endothermic or exothermic?
When the new substances were made, did it create or
destroy the matter?
WHAT FACTORS DO YOU THINK COULD EFFECT
HOW FAST THE CHEMICAL REACTION TOOK PLACE?