Kinetic molecular theoryKinetic molecular theory

Kinetic molecular theoryKinetic molecular theory

In order for molecules to react they In order for molecules to react they must collide (bang into) each other.must collide (bang into) each other.

They must collide and collide in the They must collide and collide in the exact right way (orientation)exact right way (orientation)

And with enough speedAnd with enough speed

Imagine trying to get a key into the Imagine trying to get a key into the lock with your eyes closed.lock with your eyes closed.

You need to get it in the exact right You need to get it in the exact right orientation for it to go in the hole. orientation for it to go in the hole.

The more collisions you have the The more collisions you have the higher the odds that the collisions higher the odds that the collisions will occur with the right orientation. will occur with the right orientation.

Factors determing reaction ratesFactors determing reaction rates

The more chemicals you have in a The more chemicals you have in a place the greater the chance they place the greater the chance they will collide.will collide.

So as Concentration increases so So as Concentration increases so do the amounts of reactions.do the amounts of reactions.

Surface areaSurface area

As the amount of surface area As the amount of surface area increases so do the amount of increases so do the amount of collisionscollisions

Think of a candy, which get dissolved Think of a candy, which get dissolved faster, before or after you chew it?faster, before or after you chew it?

TemperatureTemperature

As the temp goes up the molecules As the temp goes up the molecules move faster and are more likely to move faster and are more likely to collide.collide.

pressurepressure

The higher the pressure the closer The higher the pressure the closer together the molecules are….this together the molecules are….this makes them more likely to collide makes them more likely to collide and react.and react.

CatalystsCatalystsA protein that speeds up a reaction is A protein that speeds up a reaction is called a catalysts.called a catalysts.

More catalyst = more reactions.More catalyst = more reactions.

Catalysts provide an Catalysts provide an alternate reaction alternate reaction pathwaypathway

Nature of reactantsNature of reactants

Generally the more bonds that need Generally the more bonds that need to be broken the slower it will occur.to be broken the slower it will occur.

Covalent substances usually have Covalent substances usually have more bonds then ionic so they react more bonds then ionic so they react slooowwweeerrr.slooowwweeerrr.

Energy of reactionsEnergy of reactions

All chemical bonds contain energy, All chemical bonds contain energy, and in order to break them energy and in order to break them energy must go in. must go in.

Even when something gives off Even when something gives off energy we must still put in energy…energy we must still put in energy…

The amount of energy we need The amount of energy we need to invest in something to make it to invest in something to make it react is called the activation react is called the activation energyenergy

The higher the activation energy the The higher the activation energy the longer something takes to react.longer something takes to react.

If the amount of activation energy is If the amount of activation energy is lowered the reaction will happen lowered the reaction will happen faster.faster.

The way a catalyst works is by The way a catalyst works is by lowering the activation energylowering the activation energy

Heat of reactionHeat of reaction

The difference in energy the reactants The difference in energy the reactants and products is called the heat of and products is called the heat of reaction.reaction.

If something ended with more energy If something ended with more energy it is endothermic.it is endothermic.

If something ended with less energy it If something ended with less energy it is exothermic. is exothermic.

CatalystsCatalysts

Catalysts lower the activation energy Catalysts lower the activation energy by making the reaction happen inby making the reaction happen in

an an alternate routealternate route

EquilibriumEquilibrium

Until now we have only spoke about Until now we have only spoke about a reaction going in 1 direction…a reaction going in 1 direction…

But really reactions can go both But really reactions can go both ways…ways…

If A& B collide to make C & D….If A& B collide to make C & D….

Then C & D can collide to make A & BThen C & D can collide to make A & B

When a reaction occurs at equal When a reaction occurs at equal rates in both the forwards and rates in both the forwards and backwards directions it is at backwards directions it is at equilibrium. equilibrium.

The quantities are not equal!!!The quantities are not equal!!!

Just because something is in Just because something is in equilibrium does not mean there are equilibrium does not mean there are equal amounts of reactants and equal amounts of reactants and products…products…

Just that the reaction is occurring at Just that the reaction is occurring at equal rates.equal rates.

If in this class we have 31 students If in this class we have 31 students and there is always 1 student in the and there is always 1 student in the bathroombathroom

Class Class BathroomBathroom

As soon as 1 person comes in, 1 As soon as 1 person comes in, 1 goes out… There are always goes out… There are always more people in the class, but the more people in the class, but the rates of in and out are equal. rates of in and out are equal.

3 types of equilibrium3 types of equilibrium

There are 3 types of equilibreumThere are 3 types of equilibreum

PhasePhase

SolutionSolution

Chemical Chemical

When a substance is When a substance is changing changing phases both backwards and phases both backwards and forwards at equal ratesforwards at equal rates it is in it is in phase equilibriumphase equilibrium

Solution equilibriumSolution equilibriumWhen the first drop of sugar is put into When the first drop of sugar is put into water it dissolves into the water…water it dissolves into the water…

After more sugar is dissolved the water After more sugar is dissolved the water becomes full ‘saturated’ with sugar…becomes full ‘saturated’ with sugar…

After the water is saturated with sugar After the water is saturated with sugar for every drop of sugar you dissolve one for every drop of sugar you dissolve one drop has to ‘un-dissolve’ from the waterdrop has to ‘un-dissolve’ from the water. .

Chemical equilibriumChemical equilibrium

When reactants turn into products at When reactants turn into products at the same rate that the products turn the same rate that the products turn back into reactants chemical back into reactants chemical equilibrium has been reached equilibrium has been reached

Equilibriums can changeEquilibriums can change

Even if this class has an equilibreum Even if this class has an equilibreum between the bathroom and in class it between the bathroom and in class it can be distrubed.can be distrubed.

If I get really boring the equilibreum If I get really boring the equilibreum will shift to the bathroom (3 people will shift to the bathroom (3 people out at a time)out at a time)

If it’s the week before the regents it If it’s the week before the regents it will shift to the class room (no 1 out)will shift to the class room (no 1 out)

This is called Le Chatliers principleThis is called Le Chatliers principle

When a stress is added to a system When a stress is added to a system the reaction will respond to remove the reaction will respond to remove the stressthe stress

If we add chemicals on 1 side it will If we add chemicals on 1 side it will need to balance out on the other.need to balance out on the other.

If we remove chemicals from 1 side it If we remove chemicals from 1 side it will need to balance out on the otherwill need to balance out on the other

(Pen demonstration) (Pen demonstration)

Heat is a reactentHeat is a reactent

Just like changing the amount of Just like changing the amount of chemicals on 1 side can affect the chemicals on 1 side can affect the equilibrium….So can changing the equilibrium….So can changing the temptemp

NN22(g) +3H(g) +3H22(g) (g) 2NH 2NH33(g) + Heat(g) + Heat

If heat is added we shift leftIf heat is added we shift left

If heat is taken out we shift rightIf heat is taken out we shift right

PressurePressure

NN22(g) +3H(g) +3H22(g) (g) 2NH 2NH33(g) + Heat(g) + Heat

Look at this equation…Which side Look at this equation…Which side (reactant or product) seems to take (reactant or product) seems to take up more room?up more room?

NN22(g) +3H(g) +3H22(g) (g) 2NH 2NH33(g) + Heat(g) + Heat

If we put this reaction under pressure If we put this reaction under pressure which way would the reaction shift to which way would the reaction shift to ‘release’ the pressure?‘release’ the pressure?

If we gave it more pressure which If we gave it more pressure which way would it need to shift to ‘release’ way would it need to shift to ‘release’ the pressurethe pressure

The rule is:The rule is:

Increasing pressure pushes the Increasing pressure pushes the reaction towards the side with less reaction towards the side with less molecules.molecules.

Decreasing pressure pushes the Decreasing pressure pushes the reaction to the side with more reaction to the side with more molecules.molecules.

Enthalpy--- a fancy word for energyEnthalpy--- a fancy word for energy

Entropy--- a fancy word for Entropy--- a fancy word for messiness messiness

Enthalpy changesEnthalpy changes

In nature things naturally lose their In nature things naturally lose their energyenergy

Things fallThings fall

Things breakThings break

Natural reaction favor lower Natural reaction favor lower enthalpy (energy)enthalpy (energy)

EntropyEntropy

Entropy is how disordered something Entropy is how disordered something is..is..

When you wake up and shower, When you wake up and shower, brush teeth, and get dressed you brush teeth, and get dressed you have low entropyhave low entropy

By the end of the day when you look By the end of the day when you look like a slob you have high entropylike a slob you have high entropy

Low entropy High entropy Low entropy High entropy

In nature things naturally gain In nature things naturally gain entropy…They become more random entropy…They become more random with time.with time.

Natural reactions favor more Natural reactions favor more entropyentropy....

Which has more entropyWhich has more entropy

Between solid liquid & gas Between solid liquid & gas which has the most entropy, which has the most entropy, which has the least?which has the least?