ceaglex/VisualTTS_Chem · Datasets at Hugging Face

text stringlengths 19 206
dQtNrUa5Az0-036\|That's what determines the identity of the element.
dQtNrUa5Az0-038\|The mass is determined by neutrons plus protons.
dQtNrUa5Az0-039\|The electrons don't really contribute to the mass, because electrons are so tiny.
dQtNrUa5Az0-040\|They're about one 2000th the mass of a proton or a neutron.
dQtNrUa5Az0-041\|Protons and neutrons have about the same mass.
dQtNrUa5Az0-042\|So atomic mass given by the sun, atomic number determining the element of the nuclei-- of the element.
dQtNrUa5Az0-043\|The atomic number, we actually often don't write down with a symbol, because the symbol and the atomic number are redundant information.
dQtNrUa5Az0-044\|If you know the symbol, you know the number of protons in the nucleus.
dQtNrUa5Az0-045\|If you know the number of protons in the nucleus, you know the symbol or the nature of that element.
dQtNrUa5Az0-046\|So you'll often see an element written as its symbol with the atomic mass.
dQtNrUa5Az0-047\|The atomic mass is not unique, because the number of neutrons doesn't have to be unique.
dQtNrUa5Az0-049\|All of those are hydrogen, but they're different isotopes of hydrogen. They have the same number of protons with a different number of neutrons.
dQtNrUa5Az0-050\|And we can look at the isotopes of various elements on the periodic table.
aSpt0ct0aKc-000\|We define the pH scale to help us keep track of the concentration of acids and bases in solution.
aSpt0ct0aKc-001\|So pX stands for minus log base 10 of the concentration of X.
aSpt0ct0aKc-004\|So if you have a number like 10 to the minus 10, minus log of 10 to the minus 10 is 10.
aSpt0ct0aKc-005\|So you can just-- instead of looking at 10 to the minus 10, you can say, what's the magnitude, the exponent?
aSpt0ct0aKc-009\|So the pH of pure water minus log of 10 to the minus 7th-- 7.
aSpt0ct0aKc-012\|So if H3O+ goes up, OH- must go down.
aSpt0ct0aKc-013\|They're locked in synchrony with each other by the equilibrium of the autodissociation of water.
aSpt0ct0aKc-020\|So we have a scale based essentially on the exponent of the H3O+ concentration.
aSpt0ct0aKc-022\|That's the pH scale.
qZxrftuYRRQ-000\|Let's look at a chemical reaction here, the dimerization of NO2 to form N2O4.
qZxrftuYRRQ-001\|And if I tell you the reaction is spontaneous at 25 degrees C, what can you predict about the enthalpy change for that chemical reaction.
qZxrftuYRRQ-010\|We're looking at the dimerization of NO2 to form N2O4.
qZxrftuYRRQ-011\|And we're told it's spontaneous.
qZxrftuYRRQ-012\|That is, delta G is negative at 25 degrees C.
qZxrftuYRRQ-013\|When we look at this reaction, we can predict a couple of things about the entropy and the enthalpy.
qZxrftuYRRQ-014\|The entropy, for instance, in this case, decreases.
qZxrftuYRRQ-015\|And how do I know that?
qZxrftuYRRQ-016\|Well, the number of particles decrease.
qZxrftuYRRQ-017\|And if the number of particles decrease, the number of accessible microstates has to decrease as well.
qZxrftuYRRQ-021\|So that means this is a positive contribution.
qZxrftuYRRQ-022\|Minus T delta S is a positive contribution to delta G.
qZxrftuYRRQ-023\|So this doesn't favor.
qZxrftuYRRQ-024\|Entropically, this is not favored.
qZxrftuYRRQ-025\|The entropic contribution tends to make delta G positive.
qZxrftuYRRQ-026\|So we have to have an enthalpic contribution that's negative.
qZxrftuYRRQ-031\|Now, I should point out that you probably could have predicted that anyway.
qZxrftuYRRQ-032\|Because NO2 going to N2O4, the only thing that's happening here is the formation of a bond.
qZxrftuYRRQ-033\|And NO2 monomers become N2O4 dimers.
qZxrftuYRRQ-034\|A single bond is formed.
qZxrftuYRRQ-035\|And if all that's happened is a bond formation, then that must release energy.
qZxrftuYRRQ-036\|Forming bonds always releases energy.
qZxrftuYRRQ-037\|Breaking bonds always requires energy.
qZxrftuYRRQ-038\|So you could have approached this from two directions.
qZxrftuYRRQ-039\|In either case, you get an exothermic chemical reaction.
IHPOtneICaY-000\|Let's look at a situation where we take a strong acid, HCl add pH 3 and dilute that by a factor of 10.
IHPOtneICaY-001\|What is the new pH?
IHPOtneICaY-002\|So an HCl solution, I add water, dilute it by a factor of 10.
IHPOtneICaY-011\|We're talking about taking HCl, a strong acid, add pH 3, and diluting it by a factor of 10.
IHPOtneICaY-012\|Now, strong acids are particularly easy to work with and make calculations for because they completely dissociate.
IHPOtneICaY-015\|Now, you add water and dilute by a factor of 10, that means the H3O plus concentration goes from 10 to the minus 3 to 10 to the minus 4.
IHPOtneICaY-016\|A simple tenfold dilution.
IHPOtneICaY-017\|Calculate the pH now, well, the pH is 4.
IHPOtneICaY-018\|Minus log of 10 to the minus 4.
IHPOtneICaY-019\|The correct answer here is the pH changes from 3 to 4.
wrgnaV-cVrs-000\|If we look at ionic bonding, we have to transfer an electron from one element to another element.
wrgnaV-cVrs-001\|Sodium chloride, for instance, when that's formed, sodium gives up an electron and gives it to chlorine.
wrgnaV-cVrs-003\|So let's look at that.
wrgnaV-cVrs-004\|Here's the ionization energy for sodium, 496 kilojoules per mole.
wrgnaV-cVrs-005\|I have to put in 496 kilojoules per mole to pull a mole of electrons off a mole of sodium atoms.
wrgnaV-cVrs-006\|When I add a mole of electrons to a mole of chlorine atoms, what I get is 349 kilojoules released.
wrgnaV-cVrs-008\|So why does sodium chloride form?
wrgnaV-cVrs-009\|Pulling off the electron costs more than adding it to the chlorine.
wrgnaV-cVrs-010\|Well, obviously there's another component.
wrgnaV-cVrs-011\|There's several components involved.
wrgnaV-cVrs-013\|And that's a tremendously stable, strong interaction.
wrgnaV-cVrs-014\|And the formation of that lattice releases a tremendous amount of energy.
wrgnaV-cVrs-015\|So that extra release of energy, the formation of the ionic bond is what gives you enough energy to overcome the ionization energy of the sodium.
wrgnaV-cVrs-016\|In fact, the formation of sodium chloride is a spectacular reaction, and we'll look at it in the demonstration lab.
wrgnaV-cVrs-017\|We'll see metallic sodium and gaseous chlorine dramatically form sodium chloride.
wrgnaV-cVrs-019\|Sodium and chlorine form an ionic bond due mainly to the fact that the coulombic interaction is so strong.
jHbuu287uxc-000\|The natural direction of processes in the universe is determined by entropy changes.
jHbuu287uxc-001\|The natural direction is to increase the entropy of the universe.
jHbuu287uxc-002\|That is, to disperse energy over as many microstates as possible.
jHbuu287uxc-003\|But practically, it's difficult to measure the number of microstates.
jHbuu287uxc-004\|So what we need is a thermodynamic parameter, entropy, but related to a parameter that we can measure.
jHbuu287uxc-005\|And it turns out heat is that parameter that we can measure.
jHbuu287uxc-006\|And when you think about heat and work, you would probably associate entropy with heat over work, and why is that?
jHbuu287uxc-007\|Well, work is a concerted action of particles, all moving in the same direction to compress something.
jHbuu287uxc-008\|There's relatively few microstates involved with all the particles moving in the same direction.
jHbuu287uxc-009\|Where heat is the random motion of particles, and there's many microstates involved in the random motion.
jHbuu287uxc-010\|So heat is the more naturally associated parameter for entropy.
jHbuu287uxc-011\|And you can think of that-- here's a ball bouncing.
jHbuu287uxc-014\|Slight raise of temperature, more random motion of the molecules in the floor.
jHbuu287uxc-018\|So balls don't spontaneously bounce because that concerted motion is a low entropy situation.
jHbuu287uxc-019\|Now, how do we measure this heat and entropy?
jHbuu287uxc-020\|Well, it's very closely correlated.
jHbuu287uxc-021\|The entropy change is given by the heat involved in a system over the temperature.
jHbuu287uxc-023\|Heat always goes from a hotter system to a cooler system.
jHbuu287uxc-024\|In fact, some people call that the second law of thermodynamics-- heat always moves from hot to cool.
jHbuu287uxc-025\|Now, you can never get two systems that are at the same temperature to have all of the heat spontaneously move to one side.
jHbuu287uxc-026\|That would be like all the particles moving to one side of a container and leaving a vacuum on the other side.
jHbuu287uxc-027\|That's not the spontaneous direction, not the favored direction of the universe.
jHbuu287uxc-031\|You can see already-- this entropy change is smaller than this entropy change.
jHbuu287uxc-032\|This has a high temperature.
jHbuu287uxc-033\|So this negative entropy, this decrease in entropy is small.
jHbuu287uxc-034\|This increase in entropy, because the temperature is lower, is large.
jHbuu287uxc-035\|So the heat that moves has a bigger effect on the entropy of the cold system than the hot system.

dQtNrUa5Az0-036|That's what determines the identity of the element.

dQtNrUa5Az0-038|The mass is determined by neutrons plus protons.

dQtNrUa5Az0-039|The electrons don't really contribute to the mass, because electrons are so tiny.

dQtNrUa5Az0-040|They're about one 2000th the mass of a proton or a neutron.

dQtNrUa5Az0-041|Protons and neutrons have about the same mass.

dQtNrUa5Az0-042|So atomic mass given by the sun, atomic number determining the element of the nuclei-- of the element.

dQtNrUa5Az0-043|The atomic number, we actually often don't write down with a symbol, because the symbol and the atomic number are redundant information.

dQtNrUa5Az0-044|If you know the symbol, you know the number of protons in the nucleus.

dQtNrUa5Az0-045|If you know the number of protons in the nucleus, you know the symbol or the nature of that element.

dQtNrUa5Az0-046|So you'll often see an element written as its symbol with the atomic mass.

dQtNrUa5Az0-047|The atomic mass is not unique, because the number of neutrons doesn't have to be unique.

dQtNrUa5Az0-049|All of those are hydrogen, but they're different isotopes of hydrogen. They have the same number of protons with a different number of neutrons.

dQtNrUa5Az0-050|And we can look at the isotopes of various elements on the periodic table.

aSpt0ct0aKc-000|We define the pH scale to help us keep track of the concentration of acids and bases in solution.

aSpt0ct0aKc-001|So pX stands for minus log base 10 of the concentration of X.

aSpt0ct0aKc-004|So if you have a number like 10 to the minus 10, minus log of 10 to the minus 10 is 10.

aSpt0ct0aKc-005|So you can just-- instead of looking at 10 to the minus 10, you can say, what's the magnitude, the exponent?

aSpt0ct0aKc-009|So the pH of pure water minus log of 10 to the minus 7th-- 7.

aSpt0ct0aKc-012|So if H3O+ goes up, OH- must go down.

aSpt0ct0aKc-013|They're locked in synchrony with each other by the equilibrium of the autodissociation of water.

aSpt0ct0aKc-020|So we have a scale based essentially on the exponent of the H3O+ concentration.

aSpt0ct0aKc-022|That's the pH scale.

qZxrftuYRRQ-000|Let's look at a chemical reaction here, the dimerization of NO2 to form N2O4.

qZxrftuYRRQ-001|And if I tell you the reaction is spontaneous at 25 degrees C, what can you predict about the enthalpy change for that chemical reaction.

qZxrftuYRRQ-010|We're looking at the dimerization of NO2 to form N2O4.

qZxrftuYRRQ-011|And we're told it's spontaneous.

qZxrftuYRRQ-012|That is, delta G is negative at 25 degrees C.

qZxrftuYRRQ-013|When we look at this reaction, we can predict a couple of things about the entropy and the enthalpy.

qZxrftuYRRQ-014|The entropy, for instance, in this case, decreases.

qZxrftuYRRQ-015|And how do I know that?

qZxrftuYRRQ-016|Well, the number of particles decrease.

qZxrftuYRRQ-017|And if the number of particles decrease, the number of accessible microstates has to decrease as well.

qZxrftuYRRQ-021|So that means this is a positive contribution.

qZxrftuYRRQ-022|Minus T delta S is a positive contribution to delta G.

qZxrftuYRRQ-023|So this doesn't favor.

qZxrftuYRRQ-024|Entropically, this is not favored.

qZxrftuYRRQ-025|The entropic contribution tends to make delta G positive.

qZxrftuYRRQ-026|So we have to have an enthalpic contribution that's negative.

qZxrftuYRRQ-031|Now, I should point out that you probably could have predicted that anyway.

qZxrftuYRRQ-032|Because NO2 going to N2O4, the only thing that's happening here is the formation of a bond.

qZxrftuYRRQ-033|And NO2 monomers become N2O4 dimers.

qZxrftuYRRQ-034|A single bond is formed.

qZxrftuYRRQ-035|And if all that's happened is a bond formation, then that must release energy.

qZxrftuYRRQ-036|Forming bonds always releases energy.

qZxrftuYRRQ-037|Breaking bonds always requires energy.

qZxrftuYRRQ-038|So you could have approached this from two directions.

qZxrftuYRRQ-039|In either case, you get an exothermic chemical reaction.

IHPOtneICaY-000|Let's look at a situation where we take a strong acid, HCl add pH 3 and dilute that by a factor of 10.

IHPOtneICaY-001|What is the new pH?

IHPOtneICaY-002|So an HCl solution, I add water, dilute it by a factor of 10.

IHPOtneICaY-011|We're talking about taking HCl, a strong acid, add pH 3, and diluting it by a factor of 10.

IHPOtneICaY-012|Now, strong acids are particularly easy to work with and make calculations for because they completely dissociate.

IHPOtneICaY-015|Now, you add water and dilute by a factor of 10, that means the H3O plus concentration goes from 10 to the minus 3 to 10 to the minus 4.

IHPOtneICaY-016|A simple tenfold dilution.

IHPOtneICaY-017|Calculate the pH now, well, the pH is 4.

IHPOtneICaY-018|Minus log of 10 to the minus 4.

IHPOtneICaY-019|The correct answer here is the pH changes from 3 to 4.

wrgnaV-cVrs-000|If we look at ionic bonding, we have to transfer an electron from one element to another element.

wrgnaV-cVrs-001|Sodium chloride, for instance, when that's formed, sodium gives up an electron and gives it to chlorine.

wrgnaV-cVrs-003|So let's look at that.

wrgnaV-cVrs-004|Here's the ionization energy for sodium, 496 kilojoules per mole.

wrgnaV-cVrs-005|I have to put in 496 kilojoules per mole to pull a mole of electrons off a mole of sodium atoms.

wrgnaV-cVrs-006|When I add a mole of electrons to a mole of chlorine atoms, what I get is 349 kilojoules released.

wrgnaV-cVrs-008|So why does sodium chloride form?

wrgnaV-cVrs-009|Pulling off the electron costs more than adding it to the chlorine.

wrgnaV-cVrs-010|Well, obviously there's another component.

wrgnaV-cVrs-011|There's several components involved.

wrgnaV-cVrs-013|And that's a tremendously stable, strong interaction.

wrgnaV-cVrs-014|And the formation of that lattice releases a tremendous amount of energy.

wrgnaV-cVrs-015|So that extra release of energy, the formation of the ionic bond is what gives you enough energy to overcome the ionization energy of the sodium.

wrgnaV-cVrs-016|In fact, the formation of sodium chloride is a spectacular reaction, and we'll look at it in the demonstration lab.

wrgnaV-cVrs-017|We'll see metallic sodium and gaseous chlorine dramatically form sodium chloride.

wrgnaV-cVrs-019|Sodium and chlorine form an ionic bond due mainly to the fact that the coulombic interaction is so strong.

jHbuu287uxc-000|The natural direction of processes in the universe is determined by entropy changes.

jHbuu287uxc-001|The natural direction is to increase the entropy of the universe.

jHbuu287uxc-002|That is, to disperse energy over as many microstates as possible.

jHbuu287uxc-003|But practically, it's difficult to measure the number of microstates.

jHbuu287uxc-004|So what we need is a thermodynamic parameter, entropy, but related to a parameter that we can measure.

jHbuu287uxc-005|And it turns out heat is that parameter that we can measure.

jHbuu287uxc-006|And when you think about heat and work, you would probably associate entropy with heat over work, and why is that?

jHbuu287uxc-007|Well, work is a concerted action of particles, all moving in the same direction to compress something.

jHbuu287uxc-008|There's relatively few microstates involved with all the particles moving in the same direction.

jHbuu287uxc-009|Where heat is the random motion of particles, and there's many microstates involved in the random motion.

jHbuu287uxc-010|So heat is the more naturally associated parameter for entropy.

jHbuu287uxc-011|And you can think of that-- here's a ball bouncing.

jHbuu287uxc-014|Slight raise of temperature, more random motion of the molecules in the floor.

jHbuu287uxc-018|So balls don't spontaneously bounce because that concerted motion is a low entropy situation.

jHbuu287uxc-019|Now, how do we measure this heat and entropy?

jHbuu287uxc-020|Well, it's very closely correlated.

jHbuu287uxc-021|The entropy change is given by the heat involved in a system over the temperature.

jHbuu287uxc-023|Heat always goes from a hotter system to a cooler system.

jHbuu287uxc-024|In fact, some people call that the second law of thermodynamics-- heat always moves from hot to cool.

jHbuu287uxc-025|Now, you can never get two systems that are at the same temperature to have all of the heat spontaneously move to one side.

jHbuu287uxc-026|That would be like all the particles moving to one side of a container and leaving a vacuum on the other side.

jHbuu287uxc-027|That's not the spontaneous direction, not the favored direction of the universe.

jHbuu287uxc-031|You can see already-- this entropy change is smaller than this entropy change.

jHbuu287uxc-032|This has a high temperature.

jHbuu287uxc-033|So this negative entropy, this decrease in entropy is small.

jHbuu287uxc-034|This increase in entropy, because the temperature is lower, is large.

jHbuu287uxc-035|So the heat that moves has a bigger effect on the entropy of the cold system than the hot system.