Chemical Reactions
The story

Meet 2H2O
Hi there.
So is this.
This is H2O.

They weren’t always
so happy.

Hmph.
You’re out of
control
Bbbllgghh!!

Meet O2
You need me.
I’m important.

Meet H2
He’s light.
B-b-b-b-b He’s fast.
He’s crazy!

One day…
Hey!
Quit it!

One day…

Chemical Reactions
Bonds are broken and
new bonds are formed.
Bonds in H2 & O2 break.

Chemical Reactions
Bonds are broken and
new bonds are formed.
New bonds form.

Chemical Reactions
New substances
are formed.
2 gases react Water is formed

Parts of a Reaction
Reactants:
The chemicals you have before the reaction
That’d be us.
Tbtbbhth! Tbtbbhth!
H2 H2
O2

Parts of a Reaction
Products:
The substances created in the reaction
H2O H2O

Parts of a Reaction
Chemical Equation
Reactants Products

Chemical Reactions
During chemical reactions atoms are not
created or destroyed. They’re just rearranged.
2 oxygen atoms 2 oxygen atoms
4 hydrogen atoms 4 hydrogen atoms

How can you tell
if a chemical reaction
has happened?
Let me give you some hints.

Is it a chemical reaction?
If a gas is produced
it might be a chemical reaction.
Look for the bubbles!

Is it a chemical reaction?
If it changes color
it might be a chemical reaction.
Like iron rusting!

Is it a chemical reaction?
If it gets hotter
it might be a chemical reaction.

Is it a chemical reaction?
Or…if it gets colder
it might be a chemical reaction.

Exothermic Reactions
Exothermic reactions release energy.
These reactions feel hot.

Endothermic Reactions
Endothermic reactions absorb energy.
These reactions feel cold.

Image Sources
Water Molecule
http://commons.wikimedia.org/wiki/File:Water-3D-vdW.png
Oxygen and Hydrogen Molecules
http://en.wikipedia.org/wiki/File:Nitrogen-3D-vdW.png
POW!
http://www.scribbleonwalls.com/images/products/comc_05.jpg
Shiny Can
http://www.flickr.com/photos/99347433@N00/315475438/
Rusty Can
http://www.flickr.com/photos/25149679@N00/466492041/
Burning Match
http://www.flickr.com/photos/8070463@N03/3069201840/
Icicles
http://www.flickr.com/photos/14316700@N08/3075538662/
Bonfire
http://www.flickr.com/photos/dominicspics/1902322480/
Icy branches
http://www.flickr.com/photos/laszlo-photo/426155665/