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At 4:13, Sal said that the light bulb is an open system. Is that true? Shouldn't that be a closed system, as only energy is transferred from the system to the surroundings and matter is not? What is "matter" in thermodynamics anyway?

vny1qUaToHw

I agree with you that a light bulb is a closed system. Electrons flowing in and out to heat up the filament don t make it an open system. Matter refers to atoms and molecules.

When you talk about scaling the equations down (6:24), wouldn't that affect the 5 Volts on the other side as well? Does it have to do with the currents being expected to be in mA? Thank you in advance.

7I3-HAW8rmM

The scaling up/down by 1000 happens on just the left side of both equations. Every term on the left side is current x resistance. If all currents are in mA, and all resistance is in kOhms, then 10^-3 from the mA cancels out the 10^+3 from the kOhms, and you are just left with the integer parts. In Ohm s Law, the units cancel like this: kOhms x mA = 1. And for big resistors: MegOhms x uA = 1.

I'm having trouble figuring out how the algebra was worked out starting at 2:05. He mentioned how I1 is mentioned twice. How does that turn into -(R1 + R2)I1 ?

7I3-HAW8rmM

i1 appears twice in the top equation (the one right next to the Circled-3). The two terms are -R1 i1 and -R2 i1. You can factor out i1 to get ( -R1 -R2 ) i1 which is the same as - ( R1 + R2 ) i1.

At 7:07 why do you multiply the equation by 4? I can see that when you times 2 by 4 it gives you eight and it cancels out, but I don't understand why you would need to.

7I3-HAW8rmM

At this step I need to solve two equations with two unknowns (i1 and i2). The technique I m using is elimination . I took a peek at the two equations to see if I could figure out a way to cause an elimination to happen. As I wrote down the 4, I was thinking (but did not say out loud) that multiplying the top equation by 4 would cause the i2 term to cancel out. And it did!

Don't i need to use Ohm's law to figure it? 10:42 ?

7I3-HAW8rmM

Ohm s Law has already been used during the earlier steps of the Mesh Current Method to derive the mesh currents. By the time we get to 10:42 in the video, all you need to do is add or subtract mesh currents to get the element currents.

1:30 It's just like gravitational force isn't it. How the earth is pulling on the moon by it's gravitational force, but at the same time using force to keep it away isn't it? (It might seem a little bit confusing but read it over a few times to get it)

_4VC3IHbuW8

There is only the one force! It seems like there must be 2 but there is only gravity. The moon is going around the Earth (orbitting) and it is its speed that stops it from crashing into the Earth. make sense??

At 7:38, would not Q2's field affect the magnitude or effect of Q1's field?

_4VC3IHbuW8

Yes it will. But its not like that it would change the magnitude of the field.

At 11:24, isn't he electric field is 2.5 N/C when there's 4C at that point in space?

_4VC3IHbuW8

No. As the magnitude of the test charge, q, changes, so does the force it experiences from Q. If a 2 C particle experiences a force of 10 N; a 4 C particle will experience a force of bigger magnitude at the same position. Twice as big, to be exact. Static electric field of Q at a particular distance will remain constant irrespective of the magnitude of the test charge (provided Q does not move!).

Around 8:20 David says that one can determine the Force on an UNknown charge if the Electric field is known..I dont get how we can calculate the electric force without knowing the charge it acts on..

_4VC3IHbuW8

You misheard what was being said. The instructor says that if somehow you know the electric field (both the magnitude and direction) produced by a charge Q of unknown magnitude, you can calculate the force experienced by a charge of any magnitude of your choosing, placed in that field.

At 6:12 how does the charge q2 know that it has entered another charge q1's electric field

_4VC3IHbuW8

The electric field is present in free space. The charge interacts with the field. If there is no field, there is no interaction.

If u place a 4n charge in the field the field would become 10/4 why did he say 20n in 11:07

_4VC3IHbuW8

It should not become 10N/4C, you are not calculating a new value for the electric field. What you are doing is calculating the other values, charge and force. He says the electric field is always the same no matter what value the test charge has. If you increase the charge of test charge, then the force also becomes larger, they keep their ratio constant: E = F / Q.

at 4:34, why doesn't E1 exert a force on Q1?

_4VC3IHbuW8

He later tells that charge cannot exert a force on itself.

At 0:50 he says, in the hard way you gonna have 3 different accelerations but then later on in the easy way he says the acceleration is gonna be the same for all 3. Why is there a difference?

ibdidr-bEvI

I believe I know the answer to this one. The magnitude of all three accelerations are the same... only the directions are changing. This problem is just trying to find the magnitude of the acceleration so we can combine the three objects into a single system.

At 2:24, why doesn't he write sj instead of sv because j is used for vertical vectors?

RhUdv0jjfcE

The naming of the variables is just convention, it doesn t change how you do the problem. In past videos he has used Sj, Sv (for vertical), and Sy (as in the y axis). Really you could call it whatever you want but those make the most sense.

in 0:12, why does he use theta for the angle above the horizontal? can't he just use x?

RhUdv0jjfcE

yes we can use angle x instead of theta,but using theta makes the problem a little comfortable while solving compared to using angle x

At 0:10, He says that angle horizontal to the S line is Theta. How many degrees does Theta represent? Why does he use the Greek letter Theta instead of just saying the degree number? Is Theta a constant amount or a variable like X?

RhUdv0jjfcE

Theta is reserved as such for an angle. Generally, letters in the english alphabet are used as a constant value (e=2.71828 or i=rt(-1)) or are just used to substitute in values (bob is x years old, John=x+5 years old) but letters in the greek alphabet are generally used for the same functions or values (theta, alpha, beta are used for angles. delta is used for change in )

at 2:37 wouldn't the horizontal be known as vector x?

RhUdv0jjfcE

Technically, the horizontal could be known as vector x or ^i (i hat). In this video, he is labeling the horizontal component simply as S_h.

During the video, Sal talks about the Scientific Method. Does the Scientific Method include Reproducible? Also, What does Sal mean by Reproducible at 11:26?

N6IAzlugWw0

Reproducible means that, if you complete an experiment and get a certain set of results, and then give the instructions you followed for your experiment to another scientist, that other scientist should be able to get results really close to yours. Reproducible is essentially a measure of how confident you can be in your findings-- if someone else can verify your results by getting something similar, that lends a lot of credibility to your findings.

At 6:24, wouldn't it have been better to take water from the regions that Sal was testing (the lake and the ocean) and then conduct the experiment?

N6IAzlugWw0

Yes, it would definitely have been better to use pond water and sea water. Sal s experiment used distilled water and distilled water with salt in it, rather than actual pond & sea water. Pond water and sea water probably contain all sorts of bacteria and chemicals and particles that could change the freezing point- none of which can be found in distilled water.

At 9:54,it says that you have to test something out.What if scientists have already did it?

N6IAzlugWw0

This lesson was very helpful because

At 3:37 you say you couldn't test if a fairy was performing magic on the pond. But couldn't you test that with 24/7 surveillance? Common sense suggests that it would be a waste of time, but I don't think it's accurate to say it can't be tested. Doesn't a lot of science attempt to detect phenomenon that can't be observed directly?

N6IAzlugWw0

This is because even with 24/7 surveillance the fairy might not do it again and even so, it may have happened only on that one day. It might not happen at the same time the next day and is not really something that can be observed or explained using the scientific method. I do understand what you are trying to say though.

From like 8:00-8:10 when he asks if neither froze or both froze, afterwards he says we should find a different explanation but, shouldn't we try different temperatures and then find a different explanation?

N6IAzlugWw0

It depends on how saturated the solution is. The more salt the lower the freezing point.

At 6:48, why are you assuming that x is a lot smaller than 0.45. Shoudn't you want to get an exact answer instead of an approximation?

owA2rUggKoA

Because this video is called Small x approximation . So, no.

at 6:20 , which resonating structure of the acyl group is more stable ?

vFfriC55fFw

The structure with the + charge on C is more stable The structure that puts a + charge on an electronegative O atom is higher energy.

In 3:20, Sal says that the electron from the acetyl chloride is given to the AlCl3, but is the partial charge of the Aluminum strong enough to fully take away an electron from chloride? Isn't it more like a Dipole-dipole interaction?

vFfriC55fFw

The AlCl₃ is a strong Lewis acid. It is more likely that the first step is the formation of a Lewis acid/base complex: CH₃CO-Cl + AlCl₃ → CH₃CO-Cl⁺-Al⁻-Cl₃ In the next stem, the complex falls apart to form the acetyl cation. CH₃CO-Cl⁺-Al⁻Cl₃ → CH₃CO⁺ + Cl-Al⁻Cl₃.

at 9:30 where does the chloride go since the hydrogen took its electron?

vFfriC55fFw

The H doesn t take the electrons. The Cl- removed the H from the ring and formed HCl, and the electrons from the C - H sigma bond went to form the third pi bond in the benzene ring.

At 3:18 the number is 13.8629... but when i took ln of 0.5 and divided it by -0.5 i got 1.38629... Why? Shouldn't they be the same?

Hqzakjo_dYg

You are off by a factor of 10 because you should have divided by -0.05 not -0.5

At 6:26, What is "e" for? why the alphabet becomes 2.71?

Hqzakjo_dYg

e is a constant in math

What doe kt stand for? 0:18

Hqzakjo_dYg

k = any constant, and t = time.

at 3:03 what's the log inverse.

Hqzakjo_dYg

10 to the power of X i.e log (100) = 2 Therefore 10 ^ 2 = 100 which is true :) As a more general rule Log a ( b ) = Log ( a ^ b ) In chemistry log base 10 is used almost all the time so: a will always = 10 edit: Just saw that in this video Log base e is used and not log base 10. i.e the inverse of Log base 10 ( b ) = 10 ^ b and the inverse of Log base e ( b ) = e ^ b Hope that helps :)

At 3:30, Sal say that he is assuming that we are dealing with time in years. He then adds that if it were something else, we would have to convert to years. Doesn't the formula work with any time unit as long as we are consistent, and don't switch from one to another?

Hqzakjo_dYg

Yes, but if you have the half-life in years, you have to convert time to years.

At 0:58, what is k?

Hqzakjo_dYg

K Is a mathematical constant

at 4:30 what is K?

Hqzakjo_dYg

K is a constant (The German for constant is konstant) in this exponential decay example K is the number you have to times the amount of the undecayed atoms at the end of one year by to get the amount of undecayed atoms at the end of the next year.

At 7:48 Sal says that the molecules are called Ligands, at 6:44 Sal says that the molecules are called Hormones. Are the molecules called differently based on whether we're talking about Endocrine signalling or an Autocrine process?

FQFBygnIONU

Ligands are molecules that binds to a receptor. So hormones is also a ligand.

Was the reason why you decided to keep the 3-2x denominator term @11:37 (instead of assuming it to be 3) due to the magnitude of the result?

r7gTH_5XfOI

Yes. He didn t explain how he knew before. but 2x was not much smaller than 3 so the assumption would be invalid

At 8:30 why do you multiply the Ksp and the Kf to get a new K for the net reaction? What is the reasoning behind this rule?

r7gTH_5XfOI

You multiply them because you re trying to get the K for the net reaction. Multiply the K s of the individual reaction for your net reaction. If you re reversing one of the individual equations, you d change the K to 1/K.

At 7:41, Why does a light ray bend in an optically denser medium? Is the time taken for light to travel in different medium same when considering displacement of the incident ray constant in different mediums.

y55tzg_jW9I

Sal explains why it bends in the video..

At 6:43, how can you have vacuum and glass in real life?

y55tzg_jW9I

good question If you have a bottle (strong one) and you pump all the air out of it, the light will pass from the glass into vacuum as it goes into the bottle OK?

I noticed a mistake, at 5:37, when he draws the light/car going from the water medium into the vacuum, the light would bend the opposite way. The left wheel of the car would hit the vacuum first and then move FASTER, not slower, causing the light to refract in the opposite direction shown. This makes sense right?

y55tzg_jW9I

Actually, I believe what Sal said is correct. You and Sal both are correct that the front left tire would be the first to emerge from the slow medium or mud for our car analogy. It would get a grip on the better surface, the fast medium, which would be the pavement so the left side would be moving faster than the right side so the car would go in the angle that Sal showed in his example.

At 0:48, instead of "perpendicular", shouldn't it be the "normal"?

y55tzg_jW9I

It s referring to the same thing, which is the (dotted) line (that is perpendicular to the other line), and that (dotted) line is called the normal. You get what it means!

Around the 11:00, he talks about "Sin" and "Theta" what is that?

y55tzg_jW9I

Theta is the angle in question. sin(theta) = opposite/hypotenuse (for the right angle formed by angle theta)

At 0:07 , I don't get why sal says "since the surface is smooth". I thought that the angle of incidence is ALWAYS equal to the angle of reflection? Because, at the POINT at which the ray hits the surface, it bounces off in the same angle.

y55tzg_jW9I

Well, the video is about refraction. But still, the same idea holds true. If you don t have a smooth surface, you get a whole bunch of different angles of reflection, and you get a diffuse reflection instead of specular.

How is n=c/c at 13:47?

y55tzg_jW9I

When Sal says c/c that means that the speed of light in a vacuum (c) is equal to the maximum speed of light (c) so c/c equals one, and n=1

AT 5:57, how do you know if the light will refract left or right, and how big the angle will be?

y55tzg_jW9I

When going from a rarer to a denser medium, the light always refracts towards the normal at the point of contact. You know the size of the angle by knowing the refractive index and snell s law.

Between 5:33 and 5:37, Rishi mentions that if we have high levels of CO2, then we have high levels of H+. However, I have learned that as soon as H+ ions are formed, they are taken up by heamoglobin to form heamoglobinic acid, often abbreviated as HHb. This acts as a buffer... then how can the pH get low??

lVacrVMmJX8

Even the binding of H+ to Hb is an equilibrium reaction. It s not to say that every molecule of H+ is instantly mopped up by Hb. Rather, some H+ will always be in solution. Even water is in constant equilibrium with H+ (simplification).

At 1:28, the central chemoreceptors, are they actually regulatory interneurons?

lVacrVMmJX8

Based on this video, they appear to be only sensory neurons, not interneurons

why doe the voltage of the batteries add up at 3:37

j-iR7puLj6M

It doesn t. If you notice at the end the voltage of the battery is still 11V. We just care about the voltage across the terminals which is 11V however many batteries (of 11V) someone connects in parallel. That s why we model the parallel batteries with a single one, for simplicity s sake.

At 6:30, don't you need to take the inverse of that expression to get the equivalent resistance of the 2 resistors in parallel?

j-iR7puLj6M

It is a formula for two parallel resistors that is a simplified version of the parallel resistor equation you are referring to, so it already is the inverse. 1/R = 1/R1 + 1/R2, then 1/R = R2/(R1*R2) + R1/(R2*R1). 1/R= (R1+R2)/(R1R2). Finally, R=(R1R2)/(R1+R2)

At 6:30, don't you need to take the inverse of that expression to get the equivalent resistance of the 2 resistors in parallel?

j-iR7puLj6M

R1R2/(R1+R2) is actually already the inverse of the expression 1/R total.

At 6:30, don't you need to take the inverse of that expression to get the equivalent resistance of the 2 resistors in parallel?

j-iR7puLj6M

Hey, Jenna! Good question. The answer is really quite simple. In the law of resistance it says: 1/R = 1/R1 + 1/R2 ... . We can change the equation to be something like this: R = (1/R1 + 1/R2)^(-1). Now we just look inside the parentheses and we got 1/R1 + 1/R2. This can be rewritten to (R1+R2)/(R1*R2), by merging these fractions under one dividing line. So the equation now looks like this: R = ((R1+R2)/(R1*R2))^(-1). By taking the inverse of this we get R = (R1*R2)/(R1+R2).

i didnt understand the step at aroun 3:55 where the line is drawn in between the two could some explain it please?

j-iR7puLj6M

Hello Hemanth, The line is a conceptual tool used to simplify the circuit. Here we can draw the line because the circuits has the same voltage at this point. The upper branch (battery plus resistor) is the same as the lower branch (battery plus resistor). If this was a real circuit the ides still works provided the batteries have the same voltage and the resistors have the same value. Regards, APD

i am lost at 7:55 how are the equivalent resistor and r3 in series?

j-iR7puLj6M

The equivalent resistor is a single resistor representing the parallel combination of R1 and R2, with the special notation R1 || R2. That equivalent resistor has one terminal connected to R3, so therefore they are in series. All current flowing in R3 also flows in (R1 || R2).

At 4:16 when two battery's are added they voltage or current will also increased

j-iR7puLj6M

You re not adding the voltages. Theyre at the same potential as they are connected in parallel

At 4:25, the speaker says he can combine the two batteries into one big battery. What if the voltage difference between the 2 batteries were different, what would we do in that case?

j-iR7puLj6M

Then you ll have to use Kirchoff s loop rule and add up all the voltages and equate it to zero. Your variables will be in terms of i1, i2(current). On solving the different equations you get, the current will be obtained

How did you get the 2 at about 7:00 mins RR/2R

j-iR7puLj6M

We have two resistors in parallel, both with value 1.4 ohms. The formula for two parallel resistors is (R1 x R2) / (R1 + R2). If R1 = R2 (which is the case here) then the formula reduces to: (R x R) / (R + R) The numerator is R^2 and the denominator is 2R. One of the R s in the numerator cancels with the R in the denominator, leaving R/2

I am confused about connections of batteries at 3:30. Are not they cross-connected ?

j-iR7puLj6M

Hello Ozgurcan, No, the circuit is good. Observe that the batteries are in parallel with positive to positive terminal and negative to negative terminal. The batteries work together sharing the load like two people riding a tandem bicycle. Regards, APD

At 2:02, taking one battery of EMF 11V and another one, for example 15V or 17V (not the same as the previous battery), how will you find out the value of current in the particular segment?

j-iR7puLj6M

Use Kirchhoff s laws

At 3:34, why doesn't the negatively charged oxygen take a hydrogen from the acid formed when an alcohol took a Hydrogen from the positively charged oxygen at 2:36?

FGq9-R6Yw18

It certainly can. That distinction isn t extremely important in this example because the reaction is occurring in excess alcohol.

At 2:35, can the oxygen that has the negative charge grab the hydrogen, that attaches to the positive oxygen, instead of using another R-OH group to deprotonate the hydrogen? I hope you understand my question. Please help thx

FGq9-R6Yw18

It s quite probable that the same R-OH molecule facilitates the transfer of the proton from the positively charged oxygen to the negatively charged oxygen. Therefore, while Jay shows the deprotonation and the protonation as two distinct steps, they probably merge into one which amounts to the transfer of the proton from one oxygen to the other oxygen, as you suggest.

At around 3:40 in the video, when the protination of the negatively charged Oxygen is done, we form an alkyl oxide, can this cause the molecule (the hemiacetal/ketal) to react further? like a substitution reaction?

FGq9-R6Yw18

Yes, the hemiacetal/hemiketal can be protonated and react further to form an acetal/ketal.

Are the molecules formed at 10:06 are enantiomers?

FGq9-R6Yw18

Yes, the compounds are enantiomers.

Could the first intermediate (2:50) react intramolecularly? The proton would come from the positive oxygen. The negative oxygen would attack the proton and the formerly-positive oxygen would now be neutral. Is that possible?

FGq9-R6Yw18

It s possible but unlikely, because the bond angles would have to be 90 ° in the transition state. Another possible process would be intermolecular transfer between two of the intermediates, but there are so few of them that it is unlikely they would collide with each other. The most likely process is deprotonation by a solvent molecule, because there are many solvent molecules available to collide with the intermediate.

At 10:00, you show the two different possibilities formed with the OH and H. How exactly will you know when there will be two conformations or one?

FGq9-R6Yw18

Both possibilities will be formed and can inter-convert so the two anomeric forms will be in equilibrium. Which form predominates depends on the other substituents in the ring so with glucose, for example, the ratio of equatorial OH to axial OH is about 2:1.

7:35 Do the hemiacetals act as a base to deprotonate and acid to protonate or are additional reactants involved?

FGq9-R6Yw18

No, the solution is filled with base, first the molecule deprotonate and then after becoming conjugated acid, it shall donate H+ to give the product.

at 2:01, why is it called a breadboard? it isn't made of bread.

DRz9B6SHWQ4

I prefer proto board.

at 9:56 he says a decrease in adrenaline. Does that mean that the adrenal gland is always producing epinephrine?

yIWKrQTznXc

Yes. The parasympathetic and sympathetic systems work together. In most cases, your body will be functioning somewhere between hyperlazy and hyperalert. Because the systems work on a continuum, the neurotransmitters/hormones for both systems are often present.

at 4:52 what does dilate mean?

yIWKrQTznXc

By dilate, it means expansion. For emotions, we are concerned with eye dilation and lung dilation

at 3:00, I thought the adrenal glands are named because they are adjacent to the kidneys (renal)?

yIWKrQTznXc

Adrenal glands are called ad-renal because they sit atop the kidneys. Ad means on top of, and renal means pertaining to the kidneys.

@5:00 is Cyclohexanoic acid also a suitable name for Cyclohexanecarboxylic acid?

xgDuzj51tAc

Yes it is ⸂⸂⸜(രᴗര๑)⸝⸃⸃

7:17 What about the second hydrogen and oxygen in ethanol? Wont they be forming a hydrogen bond??

xgDuzj51tAc

They would form a hydrogen bond with another molecule of ethanol

@ 8:35, can someone breakdown ... ".. more non-polar a molecule becomes ... it decreases in solubility in water .." is it because the non-polar molecule is super stable in its space and doesn't want to bond w/water?

xgDuzj51tAc

A nonpolar molecule does not have dipole interactions with other molecules. Because water is polar and breaks up molecules using these dipole interactions, water can disolve polar molecules. When a molecule is more nonpolar the interactions between water and the molecule do not occur as easily and it will not dissolve as much.

At 3:24, why isn't it 2-phenolbenzoic acid instead of 2-hydroxybenzoic acid? Shouldn't the OH for labeled #2 be named a phenol since it's attached to a benzene ring?

xgDuzj51tAc

Phenol can only be used as a base name not as a substituent like that.

at 4:40 i understood with the differentiation of ω but why didn't the amplitude get squared?

xoUppFlif04

The amplitude is just a constant. The ω was squared because it appeared inside of sin(ωt), and by the chain rule, (each time we differentiate a sin or cos) it falls out. It might be better if you saw the differentiation with and without A included in the original function: f(t) = cos(ωt), f (t) = -ω sin(ωt), f (t) = -ω^2 cos(ωt). Multiplying by a constant doesn t change the inner working of the derivative, so we just have: x(t) = Acos(ωt), x (t) = -Aω sin(ωt), x (t) = -Aω^2 cos(ωt). Hope this helped!

at 1:36 , isnt it mx(double prime(t))/dt(squared)= -kx(t)? cause a=d(squared x)/dt(squared)

xoUppFlif04

There are two different notations for derivatives. One is the prime notation: mx (t) = -kx(t) This is one (correct) way of writing it. m*d^2(x(t))/(dt^2) = -kx(t) is another. They are both saying the same thing, the second derivative of the position function is equal to -kx(t). You can use either one, but don t use both at the same time.

How could we resolve the differential equation at 2:42 by analitic methods?

xoUppFlif04

You would need to use the techniques of calculus for solving differential equations. That s a college level math class for people studying engineering, math, or science.

At about 4:04, how did 'A cos(wt)' become '-Awsin(wt)'? I mean, I know the '-sin' must have come because of derivative of cosx, but how did 'w' get doubled like that?

xoUppFlif04

I see. Thank you! :)

At 6:55,how did x(t)became equal to Acos(wt)?pls help.

xoUppFlif04

If the restoring force is proportional to displacement and is toward equilibrium, then you will always get x(t)=Acos(wt) (assuming you start your measurement of t at the right point in the cycle)

At 2:20, what does x(t) mean? I saw all the video in part 3 also but I can't understand exactly what it meant. thank you!

xoUppFlif04

x(t) represents the function that relates x to t, often called x of t . This is similar to f(x) in that it has one x-value for any given t-value, and that function can be graphed. In the case of this video, it is Acos(wt) .

At 4:14,how ACos(wt) differentiated to -Awsin(wt) .Can anybody give me a full description with rules. Thank you for your help!

xoUppFlif04

derivative of cos(x) is -sin(x) derivative of cos(ax) is -asin(ax) by chain rule

At 5:18 why is the heat of vaporization of water 541 calories per gram, when it takes one calorie to raise one gram of water 1 degree. How does that end up being 541 calories to arrive at vaporization?

bVHuI_QpYIM

When you vaporize water, the temperature is not changing at all. It s changing state. That s different from heating liquid water.

At 0:50, the video says that the index of refraction is uselly a function of the wave length of light. What is the function?

HRuLhY0NAMI

it means that it depends on the wavelength. or; it is related to the wavelength

Hank mentions at 0:58 that as you grow, your cells aren't getting heavier, you're just getting more of them. When you have a person who isn't growing naturally anymore, but is still gaining weight (i.e. fat), is that still the case?

X1bmedVziGw

Oh definitely! The intake of foods into your body is what causes this. Your digestive system stores the fat away in cells called adipocytes. These are indeed cells (full of lipids I believe) and the addition of them due to what you eat and a lack of burning them away is what causes that weight gain.

At 1:44 Hank says the nucleus store instructions like how?

X1bmedVziGw

The nucleus is full of DNA, which are the blueprints for the cell.

~00:15 - The next video does not discuss why we cannot clone ourselves. We have already succeeded in cloning other animals. Why could we not be successful cloning ourselves?

X1bmedVziGw

I think he just meant we can t naturally clone ourselves, like cells do.

At 9:54 Hank states that cells divide into two identical copies. If that were true, then all our cells would be liver cells, or nerve cells, or skin cells. In fact, all our cells would still be stem cells.

X1bmedVziGw

The process you re missing from this is differentiation. Differentiation is the process of stem cells developing into specific type of cells. Stem cells will undergo mitosis to create more stem cells. Some stem cells may differentiate into skin cells. When those skin cells undergo mitosis, they will create more skin cells.

At 5:20 - Are microtubules the same as spindle fibres?

X1bmedVziGw

Spindle fibres are just aggregates of microtubules.

At 5:31, Hank says metaphase is the longest phase of mitosis. Isn't prophase the longest phase?

X1bmedVziGw

The first and longest phase of mitosis is called the prophase. It can take as much as 50 to 60 percent of the total time required to complete mitosis.

When he mentions "daughter cells" (in 9:50), are there such things as "son cells" or something like that?

X1bmedVziGw

the daughter cells in mitosis don t really have anything to do with gender. it s just a term to call the resulting identical cells. you can think of this as the same thing as when both boys and girls refer to a group of friends as guys instead of girls .

What does mitosis mean at 5:36?

X1bmedVziGw

Hank said during the biolography that mitosis is the greek word for thread.

at 2:73 hank tells that a single cell having 46 chromosomes split into two to give 2 cells with 46 chromosomes again.how is that possible?i mean each cell should have 23 chromosomes right?

X1bmedVziGw

They replicate their genome first and then divide.

At 5:29, Hank says that metaphase is the longest phase of mitosis. My biology textbook says that it is actually the shortest phase. According to the book, prophase is the longest phase and may take up to half of the total time required to complete mitosis. Is Hank wrong or is my textbook wrong?

X1bmedVziGw

My book says that prophase is the longest also.

At 0:14 Hank says that identical twins get half of their DNA from their mom and the other half from their dad... isn't that the same for the DNA of someone who isn't an identical twin?

X1bmedVziGw

Yes, but do to a process that happens during Meiosis called cross in-over, where the homologous chromosomes cross over each other and mix genes and change things around, causing people to be different. In the case of identical twins, they would have 2 identical eggs, and they would have chromosomes that matched. Hope this helps! :)

At 9:40 - Is Cytokinesis a part of Telophase or is it a separate phase entirely?

X1bmedVziGw

Cytokinesis takes place at the same time as telephase, and for that reason, I ve often seen this explained as Interphase Prophase Metaphase Anaphase Telephase and cytokinesis Interphase (repeats).

Around 4:27 Hank says that chromatin condenses around proteins to form chromosomes. Is there a name for this protein? Do we know much about it?

X1bmedVziGw

The proteins are called histones. They are rounded and sphere-like in shape. The DNA is coiled around these proteins.

At 5:28, how is metaphase the longest phase? Isn't most time spent in Prophase (still a phase of mitosis)?

X1bmedVziGw

Interphase is the longest phase- it lasts for roughly 90% of cell growth. For some cells, such as brain and spinal cord cells, which do not multiply, they remain in interphase (G1) for the entire lifetime.

at 12:10, we could have directly converted 54.5moles of water into Litres by dividing it by 22.4?

-QpkmwIoMaY

Yes, except that since 1982 the IUPAC has defined STP as 0°C and 1 bar, so the molar volume at STP is 22.7 L.

At around 2:00, what does Sal mean by 23.8 millimeters of mercury is the vapor pressure?

-QpkmwIoMaY

Millimeters of mercury (mmHg) is a unit of pressure, just like the Pascal (Pa), atmosphere (atm), or torr (Torr). 1 atm = 101 325 Pa = 760 torr = about 760 mmHg

@8:27 why does Sal use the volume's room instead of the 2.00 L of water's volume?

-QpkmwIoMaY

The vapor pressure of the liquid is the point at which as much water molecule evaporating is equal to as much water condensing. the vapor pressure gave 23.8mmHg is the partial pressure exerted by the water molecules in gas and vapor pressure of the room of open container. That s why it is necessary to consider the entire volume. I Hope that useful.

At around 9:57, why does Sal use the room temp.'s volume rather than the liquid's volume? How do you know which volume to use? Are we not trying to estimate the number of moles in liquid water that's evaporating from the open beaker system? I was a bit confused. If someone can please answer my question clearly, I would greatly appreciate it. Thanks in advance.

-QpkmwIoMaY

It is the volume of the room that is important. Water will keep evaporating until the vapour pressure of the water in the gas state equals 23.8 mmHg. If you had a bigger room, then more water would need to evaporate to reach this pressure. The volume of water is not important except in terms of whether you have enough to evaporate to reach the vapour pressure.

around 8:00 Sal says 'if more water molecules evaporate after this point the we are going to have a higher pressure which will actually favour them going into the liquid state so that will pass the equilibrium which is not likely to happen.' can someone please explain this.

-QpkmwIoMaY

At equilibrium, molecules are leaving and returning to the liquid at the same rate, and the vapour pressure is constant. I m more water molecules then enter the vapour phase, they will be hitting the surface of the liquid at a faster rate. The vapour pressure of the liquid will return to its equilibrium value.