9. I can identify stress in a system
and use LeChatelier’s Principle to show how the system would adjust to the
stress to reestablish equilibrium.
Energy: the minimum amount of energy
needed to produce an activated complex
of Reaction: the amount of heat
released or absorbed in a reaction
Reaction: a reaction that releases heat energy
Reaction: a reaction that absorbs heat energy
Complex: the temporary, unstable, intermediate union of reactants
dynamic chemical condition in which opposing reactions are proceeding at equal
rates, producing an apparent constant condition.
Kinetics deals with:
The rates of chemical reactions
The pathway by which the reaction occurs (how the reaction occurs)
Please watch the following video (~2 minutes): https://www.youtube.com/watch?v=wbGgIfHsx-I
B. Collision Theory: in order for particles to react, they must collide with each other. Each collision must have enough energy and hit in the right direction-they must be effective.
Reaction Rate depends on several factors:
1) The nature of the reactants: solutions of ionic solids react
more quickly than non-ionic solids because ions are created. Polar reacts more
quickly than non-polar.
The concentration of the reactants: ↑ the concentration ↑ the rate of
the reaction. For gases, an
increase in pressure brings the particles closer together and acts like an
increase in concentration.
Surface Area: ↑ surface area ↑the rate of the
reaction. A powdered substance will always react faster than a solid of the same amount.
temperature of the system: ↑ temperature ↑ the rate of a reaction. Why? Because more energy speeds up particles and
increases the number of collisions. The
more collisions, the more effective
collisions, the faster the reaction.
Presence of a
Catalyst: a substance that ↑ the rate of
a reaction without changing itself. **Will not begin
the reaction, it just lowers the required activation energy by providing a new
pathway for reacting particles.
Please watch the following video (~5 minutes): https://www.youtube.com/watch?v=OttRV5ykP7A&feature=emb_title
HW: 1. Please read pages 136-137 in the orange text book.
2. Please go to Castle Learning & complete 10 question Kinetics HW Lesson 1.
Friday 3/20/2020 Assignment: 1. Copy the notes (include diagrams) & watch video at bottom; 2. Complete Castle Learning 10 questions Kinetics Lesson 2 HW
Monday 3/23/2020 Assignment: 1. Read pages 138-140; 2. Complete questions 11-17 and submit a picture of your answers on remind.
of Energy in Reactions
Energy: the minimum energy needed to cause a reaction to begin
of Reaction (Enthalpy): the difference between the potential energy
of products and of the
∆H = H products – H
*Reference Table I shows the energy released/absorbed during a reaction*
Potential Energy Diagrams: illustrates the potential energy change that occurs during a chemical reaction.
a) Endothermic Reaction: reactions that absorb energy. The potential energy of the products is greater than the potential energy of the reactants. The sign for the Heat of Reaction (∆H) is positive.
reactions that release energy.
The potential energy of the products is lower than the potential energy
of the reactants. The sign for the Heat
of Reaction (∆H) is negative.
Potential Energy Diagram with a
Catalyst: *remember that a catalyst is used to speed up the reaction without being used itself. A catalyst will ONLY change the activation energy, not the potential energy of the reactants or the potential energy of the products so a catalyst will not change the heat of reaction!
**The red curve shows the addition of a catalyst.
Please watch this video **only up to 2:50 ( the remaining is material we do not need to cover) https://www.youtube.com/watch?v=fEXq_RvnYgI
Tuesday 3/24/2020 Assignment: 1. Copy the notes (do not include diagrams) & watch video at bottom
2. Complete Castle Learning 10 questions Equilibrium Lesson 3 HW
Wednesday 3/25/2020 Assignment: 1. Read pages 142-144 (top); 2. Complete questions 18-24 and submit a picture of your answers on remind.
III: Equilibrium (sometimes referred to as dynamic equilibrium)
Equilibrium is a condition that can occur only in a closed system.
Equilibrium is when the reactants become products and the products can return to reactants.
Equlibrium occurs when the rate of the forward reaction = the rate of the reverse reaction.
During equilibrium, the concentrations of the reactants and the products remains constant.
Equilibrium can be either physical or chemical.
Types of equilibrium:
1. Physical Equilibrium
Equilibrium: When the rate of
melting is equal to the rate of freezing; or when the rate of evaporation is
equal to the rate of condensation. H2O(s) <--> H2O(l) or H2O(l) <--> H2O(g)
Equilibrium: In a saturated solution (in a closed
container), when all that can be dissolved in liquid has been reached, the rate
of dissolving and the rate of recrystallizing are equal. C12H22O11(s) <--> C12H22O11(aq)
Equilibrium: In a forward reaction, the reactants form products. After a period of time the reactants begin to decrease and the products begin to increase. At this point the reaction will reverse itself so the products become reactants. This will continue until the rate of the forward reaction = the rate of the reverse reaction. CO2(g) + H2(g) <--> CO(g) + H2O(g)
Please watch the following video (~4 min) https://www.youtube.com/watch?v=dUMmoPdwBy4
Thursday 3/26/2020 Assignment: 1. Copy the notes & watch video at bottom; 2. Complete Castle Learning 10 questions Equilibrium Lesson 4 HW
Friday 3/27/2020 Assignment: 1. Read pages 144-147; 2. Complete questions 25-30 and submit a picture of your answers on remind.
IV: LeChatelier's Principle
Le Chatelier’s Principle: changes to concentration, pressure or
temperature are known as applied stresses.
This principle describes what happens to a system under such stresses.
Concentration Changes: If
there is an increase in concentration, the system will want to use up what has
been increased, therefore the reaction will shift away from the increase. If there is a decrease in concentration the
system will want to create more of what was removed, therefore the reaction
will shift towards the decrease. At equilibrium, if you add more reactants, equilibrium is upset and must return to the value so
equilibrium will shift to the product side of the reaction
*put in more = shift to the other side Add Away
*take out = remain on the same side Remove Remain
*look to see which side the heat is on, then follow the rule above: Add Away, Remove Remain if heat is added on one side, shift away from it; if heat is removed from a side, remain on the same side
Please watch the following video (~4 min) https://www.youtube.com/watch?v=XmgRRmxS3is
Monday 3/30/2020 Assignment: 1. Copy the notes (include diagrams) & watch video at bottom; 2. Complete Castle Learning 10 questions Entropy Lesson 5 HW
Tuesday 3/31/2020 Assignment: 1. Read pages 148-149; 2. Complete questions 31-39 and submit a picture of your answers on remind.
V: Entropy and Enthalpy
Entropy: (∆S) randomness or disorder in a system ∆S solid > ∆S liquid > ∆S gas
Enthalpy: (∆H) heat of reaction
Spontaneous Reactions: one that occurs naturally under a given set
Gibbs Free Energy Change: ∆G tendency of a reaction to
proceed to a minimum energy and a maximum entropy. Least energy, greatest disorder. Whether or not reactions proceed seems
to depend on the balance of two basic principles:
drive toward greater stability (reduced potential energy) -∆H
drive toward less organization (increased entropy) +∆S
Naturally the ice cube will melt and the solid will become liquid
Gibbs Free Energy Change Reaction: ∆G = ∆H - T∆S
-∆G is Spontaneous
For a reaction to occur spontaneously – more likely exothermic
reactions with an increase in entropy
Please watch the following video (up to 4:02 min - we do not need to do the calculations; watch the whole video if you are going to take AP or College Bio as you will be doing the calculations)