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Revised information on Chemical Reactions
By: Kelsey Berry
~Retyped everything except for experiments
ENERGY AND CHEMICAL REACTIONS
Chemical reactions constantly have to do with a change in
energy. Energy can’t be created or destroyed. Energy can be
absorbed or released in chemical reactions. Chemical reactions
can be endothermic or exothermic reactions.
Endothermic Reactions
These are the chemical reactions in which energy is absorbed.
Endothermic reaction means that energy is required for the
reaction to actually occur. Usually the energy that is absorbed
is often heated energy or sometimes electrical energy. Adding
the electrical energy to some metal oxides can divide them into
pure metal and pure oxygen. For example, Adding electrical
energy to sodium chloride can cause the table salt to break into
its original sodium and chlorine parts.
Exothermic Reactions
These are the chemical reactions when energy is released. The
energy that is released is originally stored in the chemical bonds
of the reactants. The heat given off causes the product to feel
hot. Any reaction that involves burning is an exothermic
reaction.
Potential Energy
It is called potential energy because it has the ability to
be converted into diferent forms of energy, and to acomplish
reactions in the process. The standard unit of measure for
potential energy is a joule.
The term
potential energy was coined by the 19th century Scottish
engineer and physicist William Rankine.
Potential energy is energy that can be stored inside
a system. It exists only when there is a force that wants to
pull an object back towards its original position, only when the
object somehow becomes displaced. This force is usually called a
restoring force. For example, when a spring is stretched to the
left, it exerts a force to the right so as to return to its
original, unstretched position.
According
to the Principle of Conservation of Energy, energy can’t be
created nor destroyed; this means that the energy can’t
disappear. Instead it can be stored as potential energy.
Chemical Potential
energy, for example, the energy stored in fossil fuels, is due to
the Coulomb Force which is rearrangement of the positions of
the electrons and nuclei, in atoms and the molecules.
Activation Energy
In chemistry, activation energy is also called midnight
energy. It happens to be a term introduced in 1889 by a
Swedish scientist called Svante Arrhenius.
It is
defined as the energy that must be overcome in order for the
chemical reaction to take place. Arrhenius’s research was a
continuation of the work on the theories of reaction rate done
by a Serbian physicist named Nebojsa Lekovic.
Activation energy may also be defined as the least amount
of energy necessary for a chemical reaction to take place.
For a chemical reaction to be noticeable,
there should be noticeable number of molecules with the energy
equal or greater than the activation energy level.
Reactants and products
Reactants are the substances that enter into the reaction, and
the products are the substances that are present at the end of
the reaction, and are due to the chemical reaction of the
reactants.
An example of a chemical reaction is when you add sodium
hydroxide to hydrochloric acid. The reactants are sodium
hydroxide and hydrochloric acid, and the products are water and
sodium chloride.
NaOH (aq) + HCl (aq) = H2O (l) + NaCl (aq)
Signs of a Chemical Reaction
-Bubbles(like opening a soda can)
-heat
-cold
-giving off light
-change of color
-formation of gas
-odor change
-energy produced
The Law of Conservation of Mass
The Law of Conservation of Mass was officially established
in the year 1789 by the French Chemist, Antoine Lavoisier.
The Law of Conservation of Mass states that mass is neither
lost nor gained in chemical reactions, it states that it simply
changes form. For that reason, if you had a certain number of
atoms of a certain element on the left side of a chemical
reaction equation, then you would have to have the same
number of atoms of that element on the right side of the
equation. This entails that mass can also be conserved during a
chemical reaction.
Combustion
A combustion reaction can occur when oxygen combines with
another compound so it will end up forming water or carbon
dioxide. These reactions produce heat so they are called
exothermic reactions.
EXAMPLE:
C10H8 + 12 O2 ---------------10 CO2 + 4 H20
Synthesis
During a synthesis reaction two or more simple substances
combine which forms a more complex substance.
EXAMPLE:
Oxygen + hydrogen combine to create water
2 H2 + O2--------------------2H2O
Double Replacement
During a double replacement reaction the parts of 2 compounds
switch places which causes a new compound to form.
EXAMPLE:
AgNO3 + NaCl-------------------AgCl + NaNO3
Decomposition
During a decomposition reaction a complex substance will break
down and form into simpler parts. Synthesis and decomposition
happen to have the same effect on substances.
EXAMPLE:
2 H2O --------------------2 H2 + O2
Single Replacement
During a single replacement reaction a single uncombined
element replaces another in a compound.
EXAMPLE:
Zn + 2 HCl-------------------ZnCl2 + H2
Bibliography
INFORMATION BIBLIOGRAPHY
~Carpi, Anthony. “Chemical Reactions.” Chemical Reactions.
http://web.jjay.cuny.edu/~acarpi/NSC/6-react.htm (19981999).
~”Types of Chemical Reactions.” Chemical Reactions.
http://educ.queensu.ca/~science/main/concept/chem/c02/c02mai
n.htm.
~Eigen, Manfred; Ostwald, Wilhelm; Herschbach, Dudley R.;
Hoff, Jacobus Henricus van ’t. “Chemical Reactions.” Chemical
Reactions.
http://www.britannica.com/EBchecked/topic/108802/chemicalreaction/49377/Basic-concepts-of-chemical-reactions.
~”Reaction (Overview).” Chemical Reactions. http://www.
chem4kids.com/files/react_intro.html (1997-2007).
~Barrans, Richard. “Ask a Scientist.” Chemical Reaction Archive.
http://www.newton.dep.anl.gov/askasci/chem00/chem00971.ht
m (Feb 3, 2003).
~Helmenstine, Anne. “Types of Chemical Reactions.” Chemical
Reactions. http://chemistry.about.com/od/chemicalreactions
/a/reactiontypes.htm (2008)
~”Decomposition Reaction Lab.” Chemical Reaction Labs.
http://library.thinkquest.org/18406/drlab.htm.
~”Single Replacement Lab.” Chemical Reaction Labs.
http://library.thinkquest.org/18406/sdlab.htm.
PICTURE BIBLIOGRAPHY
(I used Google images for all pictures)
~http://popsci.typepad.com/photos/uncategorized/2007/11/27/s
helterbakingsoda_2.jpg.
~http://www.webdesign.org/img_articles/7477/flame-slice_11.gif.
~http://www.freefoto.com/images/33/15/33_15_10---FireFlame-Texture_web.jpg.
~http://www.nugentec.com/images/rust.jpg.
~http://www.lowellfoods.com/files/image/products/grocery/prese
rves/vinegar.jpg.
~http://www1.istockphoto.com/file_thumbview_approve/878847
/2/istockphoto_878847_steel_wool.jpg.
~http://www.lakewoodconferences.com/direct/dbimage/5014692
6/Citric_Acid.jpg.
~http://www.maths.tcd.ie/~foams/GALERY/Jelly_20foam.JPG.
~http://www.metalChina.cn/en/wire/shengjiagong/images/dinglei01.jpg.
~http://www.stainedfloor.com/CopperSulfate1.jpg.