By Zanman  

Chemical Reactions

Chemical Reaction Basics Only the electrons are

affected in a chemical reaction.

During a chemical reaction, chemical bonds are either made or broken.

The substances initially involved in the chemical reactions are called the reactants.

Unlike a reactant, though, a catalyst increases the rate of a chemical reaction but is not consumed.

A chemical reaction produces one or more products, which most of the time have different properties than the reactants.

http://en.wikipedia.org/wiki/Image:Hydrochloric_acid_ammonia.jpg

Signs of a Chemical Reaction There are several

signs to tell that a chemical reaction has taken place.

http://www.dkimages.com/discover/previews/857/35080206.jpg

1. A change in temperature

http://z.about.com/d/chemistry/1/G/5/a/demonstration.jpg

2. A change in color

3. A gas is produced

http://amazingrust.com/Experiments/how_to/Images/Chlorine_gas.jpg

4. Precipitate forms

http://www.carnicom.com/sheil/beaker2.jpg

5. Energy is produced

http://www.scienceproject.com/projects/intro/intermediate/images/IC003.jpg

The Law of Conservation of MassThe Law of Conservation of Mass

The Law of Conservation of Mass says that the of mass a The Law of Conservation of Mass says that the of mass a closed system will remain constant, regardless of the closed system will remain constant, regardless of the processes acting inside the system. processes acting inside the system.

Basically, it says that matter cannot be destroyed or created.Basically, it says that matter cannot be destroyed or created.

This relates to chemical reactions because it means that This relates to chemical reactions because it means that even though a chemical bond is forming or breaking, the even though a chemical bond is forming or breaking, the matter in the reaction is staying the same. matter in the reaction is staying the same.

Energy & Chemical ReactionsEnergy & Chemical ReactionsA chemical reaction can absorb energy and cool down. An A chemical reaction can absorb energy and cool down. An endothermic reaction is a chemical reaction that does this. endothermic reaction is a chemical reaction that does this.

•Photosynthesis is an example of an endothermic reactionPhotosynthesis is an example of an endothermic reaction•dissolving ammonium chloride in waterdissolving ammonium chloride in water •reaction of barium hydroxide octahydrate crystals with dry ammonium chloride

Or it can release energy and heat up. An Or it can release energy and heat up. An exothermic reaction is a chemical reaction that exothermic reaction is a chemical reaction that releases heat. releases heat.

reactants → products + energy reactants → products + energy

Example:Example:•Na(s) + 0.5ClNa(s) + 0.5Cl22(s) = NaCl(s)(s) = NaCl(s)

• Sodium and chlorine to make table salt, Sodium and chlorine to make table salt, which produces 411 Kj of energy for every which produces 411 Kj of energy for every mole of salt produced. mole of salt produced.

•CC33HH88 + 5O + 5O22 ---> 4H ---> 4H22O + 3COO + 3CO22 + energy + energy• propane + oxygen  yields water + carbon propane + oxygen  yields water + carbon

dioxide + energydioxide + energy http://www.popsci.com/files/imagecache/photogallery_image/files/articles/salt_ss_fire2.jpg

http://chemistry.about.com/cs/generalchemistry/a/aa051903a.htm

EnergyEnergy

Activation energy is the minimum amount of energy needed to Activation energy is the minimum amount of energy needed to get molecules and/or atoms to start a reaction.get molecules and/or atoms to start a reaction.

Energy is always released or absorbed in a chemical reaction, Energy is always released or absorbed in a chemical reaction, but never destroyed or created. but never destroyed or created. This is called the Law of Conservation of EnergyThis is called the Law of Conservation of Energy

Also called midnight energy. Also called midnight energy. Examples: Examples:

When bonding chlorine and sodium, you need to add water first. When bonding chlorine and sodium, you need to add water first. This amount of energy is the activation energy. This amount of energy is the activation energy.

Boiling water needs to reach a temperature of 212Boiling water needs to reach a temperature of 212ooF in order to boil, F in order to boil, so the amount of energy it takes to get the water to 212so the amount of energy it takes to get the water to 212ooF would be F would be the activation energy. the activation energy.

http://wiki.answers.com/Q/How_is_energy_involved_in_chemical_and_physical_changes http://en.wikipedia.org/wiki/Activation_energy http://discover.edventures.com/functions/termlib.php?action=&termid=173&alpha=a&searchString=

http://www.cobb.k12.ga.us/~simpson/Teacher%20Sites/Teacher%20Sites/Electricity.jpg

Chemical Potential Energy

Chemical potential energy is a form of potential energy related to the arrangement of atoms and molecules, which could be the result of chemical bonds within the molecule.

Chemical potential energy can be transformed into other forms of energy by a chemical reaction.

Examples:When a fuel goes through combustion, the chemical energy is transformed into heat.

Photosynthesis turns solar energy to chemical energy.

When methane molecules hits oxygen atoms at high speeds (caused by a flame, etc.), there is a rearrangement of the atoms. Two of the oxygen atoms will combine with the four hydrogen (H) atoms to form two water molecules (H2O). The other two oxygen atoms will combine with methane's carbon atom to form carbon dioxide.

http://www.chemistryland.com/CHM107/Energy/MethaneCombustWhiteSimple.jpg

Types of Reactions:

There are several different types of reactions. They are:

Synthesis Decomposition Combustion Single Replacement Double Replacement

http://www.oralchelation.com/technical/images/atom2.jpgAll of the slides mentioned here use info from:http://www.usoe.k12.ut.us/curr/science/sciber00/8th/matter/sciber/chemtype.htm

Synthesis Synthesis is a type of reaction that combines two chemicals

together in a chemical reactor to get one or more products. By looking at the formula, you will see that the two elements

that were before alone are now bonded together into a compound.

Examples: 2Na + Cl2 → 2 NaCl (formation of table salt)

S + O2 → SO2 (formation of sulfur dioxide)

4 Fe + 3 O2 → 2 Fe203 (iron rusting)

CO2 + H2O → H2CO3 (carbon dioxide dissolving and reacting

with water to form carbonic acid)

http://www.dtsc.ca.gov/PollutionPrevention/images/chemicals.JPG

Decomposition is when a more complex substance breaks down into its simpler parts.

It is basically the opposite of synthesis. By looking at the equation, you will see that

the elements in the compound are now uncombined and are alone.

Example:2H2O 2H2 + 02

http://www.zamondo.com/images/lrg_Decomposition.jpg

Decomposition

Combustion Combustion is when a fuel and an oxidant react

exothermically with the productions of heat and light (Flames, or a glow).

Basically, combustion is when something burns.

http://www.boygeniusreport.com/wp-content/uploads/image/explosion.jpg

http://www.freefoto.com/images/33/15/33_15_10---Fire-Flame-Texture_web.jpg

Single Replacement In a single replacement reaction, one uncombined

element replaces a single element in a compound It yields two products If you look at the equation, then you will see that

one of the elements from the compound is alone and the element that was alone before is now in the compound.

Example:Zn + 2HCl ZnCl2 + H2

Double Replacement In a double replacement, two compounds switch their elements to form two

new compounds It creates two new products If you look at the reaction, then you will see that the elements of the first

compound and the second compound are with different elements than before.Example:

AB + CD AC + BD

Pb(NO3)2 (aq) + 2KI (aq) --> 2KNO3 (aq) + PbI2 (s)

http://www.nitrogenorder.org/experiment/dblreplace.shtml

1. Add the potassium iodide to the beaker.

2. Pour the lead (II) nitrate into the beaker.

3. Without splashing, stir the contents of the beaker with the stirring rod for three minutes.

Combining lead (II) nitrate and potassium iodide

Opening Page Image Credits 

Opening Page Image Credits:• http://chemcarling.googlepages.com/figure-01-39.jpg/figure-01-39-full.jpg

 • http://www.7art-screensavers.com/screens/3d-chemical-elements/borum-atom-quarks.jpg

 • http://grandinetti.org/Teaching/Chem121/assets/caffeine.gif

 • http://facstaff.gpc.edu/~pgore/PhysicalScience/atom-with-electrons.gif

 • http://sub.allaboutcircuits.com/images/00257.png

 • http://www.corrosionsource.com/handbook/periodic/periodic_table.gif

 • http://www.personal.psu.edu/staff/m/b/mbt102/bisci4online/chemistry/structureatoms.jpg

 •  http://focus.aps.org/files/focus/v19/st19/water.jpgOther:• http://en.wikipedia.org/wiki/

• http://www.usoe.k12.ut.us/curr/science/sciber00/8th/matter/sciber/chemtype.htm

• http://answers.yahoo.com/question/index?qid=20081109193239AAsxvbW