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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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collision theory
Collision Theory
  • For chemical reaction to happen, their particles (atoms, molecules, or ions) must collide, and the collisions must result in interactions between species.
slide3

Chemical reactions

aren’t for sissies!

For any reaction

to happen there

must be a collision!

I’m afraid of

collisions!

Don’t hurt me!

collision theory1
Collision Theory

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.

slide6
Or if the orientation of the molecules is wrong (charges not aligned, ect.) There is no reaction.

+

-

H

H

O

collision theory2
Collision Theory

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 theory3
Collision Theory

Collision theory states that sufficiently strong collisions between molecules, in the correct orientation, must happen for reactions to occur.

factors that effect reactions
Factors That Effect Reactions

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!

1 temperature
1. Temperature

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.

2 concentration
2. Concentration

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.

increased concentration

Too crowded!

Increased concentration

= more collisions, thus faster reaction

decreased concentration
Decreased concentration

= fewer collisions, thus slower reaction

3 particle size
3. Particle Size

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

surface area from large to small
Surface area, From Large to Small

Chunks or Lumps Large

Pieces or granules

Powder or dust Small

4 catalysts
4. Catalysts

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.

energy is part of reactions
Energy is part of Reactions

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.

slide18

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.

don t forget
Don’t Forget…

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!

review
Review!
  • According to Collision Theory, What needs to happen in order for a successful chemical reaction to occur?
  • Molecules need to collide with enough energy
  • Molecules need to collide in the correct orientation
  • Molecules need to collide slowly
  • Both A and B
review1
Review!
  • Which choice would NOT increase the rate of a chemical reaction?
  • Increasing the concentration of molecules
  • Increasing the size of the particles
  • Adding a catalyst
  • Increasing the temperature
true false
True/False
  • A catalyst is used to speed up chemical reactions
  • True
  • False
true false1
True/False
  • A catalyst is used up in a chemical reaction (meaning you can’t reuse it again!)
  • True
  • False
fecl 3 s o 2 g fe 2 o 3 aq cl 2 g

HCl

FeCl3(s) + O2(g) Fe2O3(aq) + Cl2(g)
  • Which substance in the equation is a solid?
  • FeCl3
  • O2
  • Fe2O3
  • Cl2
  • HCl
fecl 3 s o 2 g fe 2 o 3 aq cl 2 g1

HCl

FeCl3(s) + O2(g) Fe2O3(aq) + Cl2(g)
  • Which substance in the equation is dissolved in water (aqueous)?
  • FeCl3
  • O2
  • Fe2O3
  • Cl2
  • HCl
fecl 3 s o 2 g fe 2 o 3 aq cl 2 g2

HCl

FeCl3(s) + O2(g) Fe2O3(aq) + Cl2(g)
  • Which substance in the equation represents a catalyst?
  • FeCl3
  • O2
  • Fe2O3
  • Cl2
  • HCl
types of chemical reactions
Types of Chemical Reactions

While there are literally thousands of different kinds of chemical reactions, most can be classified into 5 main types:

slide28

Synthesis (or addition or combination)

  • Decomposition
  • Single displacement (or single replacement
  • Double displacement (or double replacement)
  • Combustion
1 synthesis
1. Synthesis

Synthesis reactions occur when two or more reactants combine to form one new compound product.

A + X AX

2Mg + O2 2 MgO

real life please
Real life please….

Rust is a synthesis reaction

4Fe + 3O2 Fe2O3

many plastics are made with synthesis reactions
Many plastics are made with synthesis reactions….

Think of how often in a day you encounter plastic… think synthesis A + X AX

1 synthesis1
1. Synthesis

Bella

Edward

Our romance starts when Bella moved to Oregon, and fell in love with Edward…

1 synthesis2
1. Synthesis

=

Bellward

True Love…COMBINE together

2 decomposition
2. Decomposition

Occurs when one reactant decomposes to form two or more products. Decomposition is the opposite of synthesis.

AX A + X

2HgO 2Hg + O2

2 decomposition1
2. Decomposition

Rihanna&Chris

Some couples are just not meant to be…

2 decomposition2
2. Decomposition

=

Rihanna

+

Chris

…some couples SPLIT after a little “heat”

3 single displacement
3. Single Displacement

A lone element replaces an element with a similar charge in a compound.

A + BC AC + B

H2 + CuO H2O + Cu

real life please1
Real life please…
  • Never store acids in metal containers because

2Al + 6HCl 2AlCl3 + 3H2

The metal container will dissolve,

leaking the acid everywhere…

4 double displacement
4. Double Displacement

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

real life please2
Real life please…

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.

4 double replacement
4. Double Replacement

Addison&McDreamy + Meredith&McSteamy

Some couples are not satisfied with one another…and well…

4 double replacement1
4. Double Replacement

= Addison&McSteamy + Meredith&McDreamy

…couples SWITCH partners

5 combustion
5. Combustion

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

hydrocarbons for combustion
Hydrocarbons for combustion

CH4 Methane - Natural gas

C3H8 Propane – Gas grills

C4H10 Butane - Lighters

real life examples
Real Life Examples

Complete combustion of methane:

(burns with a blue flame – complete combustion very rare)

CH4 + 2O2 CO2 + 2H2O

slide46

Incomplete combustion:

Carbon doesn’t completely burn, some “ash” or “soot” left over. Flame burns with any color than blue.