February 16, 2011

Today in class we learned a couple of new things. But before I explain to you what we learned let me just quickly tell you what we got back and what is for homework.

What We Got Back:
- Virtual Lab
- Lab:5B
Quiz; (Is Coming Back Next Class)

Homework:
- Worksheet; Calculations with exothermic and endothermic reactions

Now for what we learned in class was endothermic reactions, exothermic reactions, and energy diagrams.

Endothermic Reactions + Exothermic Reactions:
You are probably thinking, "well first of all what the heck are these 'reactions'?" and "what is the difference between them?" Well don't worry because these two are actually quite simple to learn! Here are some definitions, facts and examples...........
- definition of endothermic reaction =
a chemical reaction accompanied by the absorption of heat.
- definition of exothermic reaction =
a chemical reaction accompanied by the release of heat.
- add energy to break bonds and gives off to join together
- more energy than it gives off to form bonds = endothermic
- less energy than it gives off to form bonds = exothermic
- enthalpy (H) = the heat contained in the system
- examples of endothermic reactions = cooking an egg, baking bread, melting ice cubes, evaporating liquid water, splitting a gas molecule, mixing water and ammonium nitrate, and producing sugar by photosynthesis.
- examples of exothermic reactions = all combustion reactions (fires), explosions, making ice cubes, formation of snow in clouds, a candle flame, rusting iron, burning sugar, and nuclear fission.

Energy Diagrams:
- definition = a graph of the energy of a reaction against the process of the reaction.
Terms:
- Energy of activated complex; potential energy of the transition state betweeen reactants and products.
- Activation Energy; the energy that must be added to get the reaction to progress.
- /\H; the change in potential energy during the reaction.
- Example of an endothermic energy diagram with terms (down below):

- Can you figure out where the terms belong ?!?!?! Without looking above!!!!! 
 

- Example of an exothermic energy diagram with terms (down below):

- Can you figure out where the terms belong ?!?!?! Without looking above!!!!! 


Energy in Equations:
- exothermic reactions have the energy on the right and a negative /\H
- endothermic reactions have the energy on the left and a postive /\H
example = CH4 + 2O2 g CO2 + H2O
                Higher Energy    Lower Energy


Whewww, alot of information but with practice and patience you can master it! :) Now for the rest of this entry I am going to give you some youtube videos, worksheets, images doing with endothermic vs. exothermic, and then for your treat you get crosswords! Yay!

Youtube:
1)
2) http://www.youtube.com/watch?v=5RJLvQXce4A&feature=related
3) http://www.youtube.com/watch?v=80Q3GgeeIVM&feature=related

Worksheets + Information:
1) http://chemistry.about.com/od/lecturenotesl3/a/endorxns.htm
2) http://chemistry.about.com/cs/generalchemistry/a/aa051903a.htm
3) http://www.emsb.qc.ca/laurenhill/science/exo.html
4) http://wiki.answers.com/Q/How_do_you_determine_if_a_reaction_is_endothermic_or_exothermic
5) http://antoine.frostburg.edu/chem/senese/101/thermo/faq/exothermic-endothermic-examples.shtml
6) http://www.800mainstreet.com/7/0007-002-exo_endothermic.html
7) http://www.sciencegeek.net/Chemistry/taters/energydiagram.htm
8) http://www.kentchemistry.com/links/Kinetics/PEDiagrams.htm
9) http://www.saskschools.ca/curr_content/chem30_05/2_kinetics/kinetics3_2.htm

Images: (Guess which are Exothermic or Endothermic!!!!)








Crosswords:
1) http://www.creative-chemistry.org.uk/funstuff/xword/
2) http://users.rcn.com/fvirzi/x-word-home.htm
3) http://www.armoredpenguin.com/crossword/Data/2009.11/0114/01145050.358.htmlhttp://www.youtube.com/watch?v=G1k3zQy936U