Chemical Reactions. Collision Theory. For chemical reaction to happen, their particles (atoms, molecules, or ions) must collide, and the collisions must result in interactions between species. Chemical reactions aren’t for sissies! For any reaction to happen there must be a collision!.
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aren’t for sissies!
For any reaction
to happen there
must be a collision!
I’m afraid of
Don’t hurt me!
The “interaction” piece of collision theory is critical. If the molecules’ collision is too gentle, they just gently bounce off each other with no reaction.
For two molecules to react, they must collide with enough energy to move valence electrons and disrupt the bonds of the molecules, and be correctly oriented.
Collision theory states that sufficiently strong collisions between molecules, in the correct orientation, must happen for reactions to occur.
Again, a reaction between two molecules can only occur when a collision occurs between the two molecules.
I’m ready for a chemical reaction! Let’s collide!
Raising the temperature increases the speed at which the molecules move.
When molecules move faster, more collision occur, thus making the reaction proceed faster. The opposite is true for decreasing the temp.
When the concentration is increased, the number of molecules are increased. When there are more molecules, more collisions occur thus making the reaction proceed faster. The opposite is true for decreasing the concentration.
= fewer collisions, thus slower reaction
When the size of the particles are smaller the surface area is increased. This provides access to a greater number of molecuels and increases the speed of the reaction. The opposite is true for using larger particle sizes.
Large particle, slow reaction
Small particles, fast reaction
Chunks or Lumps Large
Pieces or granules
Powder or dust Small
Even though a catalyst is never used up in a reaction, their presence can speed up a reaction by lowering the energy it takes for collisions to occur.
Exothermic Reaction – when energy is released during a reaction it is called an exothermic reaction. This is observed as an increase in temperature. The words heat, light, or energy are written as a product.
Endothermic reaction – when energy is absorbed or taken in during a chemical reaction. This is observed as a decrease in temperature. The words heat, light, or energy are written as a reactant.
Chemical reactions must follow the Law of Conservation of Mass, which states that mass is neither created nor destroyed. The form of matter may change, but the TOTAL amount of mass stays constant. This law also means that the number of atoms must stay the same too!
While there are literally thousands of different kinds of chemical reactions, most can be classified into 5 main types:
Synthesis reactions occur when two or more reactants combine to form one new compound product.
A + X AX
2Mg + O2 2 MgO
Rust is a synthesis reaction
4Fe + 3O2 Fe2O3
Think of how often in a day you encounter plastic… think synthesis A + X AX
Our romance starts when Bella moved to Oregon, and fell in love with Edward…
True Love…COMBINE together
Occurs when one reactant decomposes to form two or more products. Decomposition is the opposite of synthesis.
AX A + X
2HgO 2Hg + O2
Some couples are just not meant to be…
…some couples SPLIT after a little “heat”
A lone element replaces an element with a similar charge in a compound.
A + BC AC + B
H2 + CuO H2O + Cu
2Al + 6HCl 2AlCl3 + 3H2
The metal container will dissolve,
leaking the acid everywhere…
Occurs when positive and negative ions switch places. The old switch-a-roo!
Make sure to match positive and negative ions together!
AB + CD AD BC
FeS + 2HCl FeCl2 + H2S
2HCl + Mg(OH)2 MgCl2 + 2H2O
When your stomach is upset (heartburn, ect) and there is excess stomach acid, TUMS or milk of magnesia is used to neutralize the excess stomach acid.
Addison&McDreamy + Meredith&McSteamy
Some couples are not satisfied with one another…and well…
= Addison&McSteamy + Meredith&McDreamy
…couples SWITCH partners
Occurs when a hydrocarbon (a compound containing only hydrogen and carbon) burns by combining with oxygen. Carbon dioxide and water are the only products.
Ex. C2H6 + 7O2 4CO2 + 6H2O
CH4 Methane - Natural gas
C3H8 Propane – Gas grills
C4H10 Butane - Lighters
Complete combustion of methane:
(burns with a blue flame – complete combustion very rare)
CH4 + 2O2 CO2 + 2H2O
Carbon doesn’t completely burn, some “ash” or “soot” left over. Flame burns with any color than blue.