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Chemical Reactions

Chemical Reactions. By Zanman. http://en.wikipedia.org/wiki/Image:Hydrochloric_acid_ammonia.jpg. Chemical Reaction Basics. Only the electrons are affected in a chemical reaction. During a chemical reaction, chemical bonds are either made or broken.

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Chemical Reactions

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  1. Chemical Reactions By Zanman

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

  3. A change in temperature 3. A gas is produced http://www.dkimages.com/discover/previews/857/35080206.jpg 2. A change in color http://z.about.com/d/chemistry/1/G/5/a/demonstration.jpg http://amazingrust.com/Experiments/how_to/Images/Chlorine_gas.jpg Signs of a Chemical Reaction There are several signs to tell that a chemical reaction has taken place. 4. Precipitate forms http://www.carnicom.com/sheil/beaker2.jpg 5. Energy is produced http://www.scienceproject.com/projects/intro/intermediate/images/IC003.jpg

  4. The Law of Conservation of Mass • The Law of Conservation of Mass says that the of mass a closed system will remain constant, regardless of the processes acting inside the system. • Basically, it says that matter cannot be destroyed or created. • This relates to chemical reactions because it means that even though a chemical bond is forming or breaking, the matter in the reaction is staying the same.

  5. A chemical reaction can absorb energy and cool down. An endothermic reaction is a chemical reaction that does this. • Photosynthesis is an example of an endothermic reaction • dissolving ammonium chloride in water • reaction of barium hydroxide octahydrate crystals with dry ammonium chloride http://chemistry.about.com/cs/generalchemistry/a/aa051903a.htm • Or it can release energy and heat up. An exothermic reaction is a chemical reaction that releases heat. • reactants → products + energy • Example: • Na(s) + 0.5Cl2(s) = NaCl(s) • Sodium and chlorine to make table salt, which produces 411 Kj of energy for every mole of salt produced. • C3H8 + 5O2 ---> 4H2O + 3CO2 + energy • propane + oxygen  yields water + carbon dioxide + energy http://www.popsci.com/files/imagecache/photogallery_image/files/articles/salt_ss_fire2.jpg Energy & Chemical Reactions

  6. Energy Activation energy is the minimum amount of energy needed to get molecules and/or atoms to start a reaction. Energy is always released or absorbed in a chemical reaction, but never destroyed or created. This is called the Law of Conservation of Energy Also called midnight energy. Examples: When bonding chlorine and sodium, you need to add water first. This amount of energy is the activation energy. Boiling water needs to reach a temperature of 212oF in order to boil, so the amount of energy it takes to get the water to 212oF would be the activation energy. http://www.cobb.k12.ga.us/~simpson/Teacher%20Sites/Teacher%20Sites/Electricity.jpg • 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=

  7. 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 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.

  8. Types of Reactions: There are several different types of reactions. They are: • Synthesis • Decomposition • Combustion • Single Replacement • Double Replacement All of the slides mentioned here use info from: http://www.usoe.k12.ut.us/curr/science/sciber00/8th/matter/sciber/chemtype.htm http://www.oralchelation.com/technical/images/atom2.jpg

  9. 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

  10. Decomposition • 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

  11. http://www.freefoto.com/images/33/15/33_15_10---Fire-Flame-Texture_web.jpghttp://www.freefoto.com/images/33/15/33_15_10---Fire-Flame-Texture_web.jpg http://www.boygeniusreport.com/wp-content/uploads/image/explosion.jpg 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.

  12. Example: Zn + 2HCl  ZnCl2 + H2 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.

  13. Combining lead (II) nitrate and potassium iodide • Add the potassium iodide to the beaker. • Pour the lead (II) nitrate into the beaker. • Without splashing, stir the contents of the beaker with the stirring rod for three minutes. Pb(NO3)2 (aq) + 2KI (aq) --> 2KNO3 (aq) + PbI2 (s) http://www.nitrogenorder.org/experiment/dblreplace.shtml 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

  14. 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.jpg • Other: • 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

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