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QUESTÕES de NATUREZA que SEMPRE CAEM no ENEM! (+43 ACERTOS) — Transcript

by Marcos Vasconcellos · 11,165 words · 1,813 segments · language en · Watch on YouTube

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0:00In this video, I will teach you how to
0:02get questions right that appear every
0:04year on the ENEM Natural Sciences test.
0:07If you stay until the end of this video
0:10, you will be able to secure some extra
0:12points on the Natural Sciences test,
0:14since it is very likely that the
0:16questions I'll work on here today will
0:19be on this year's ENEM.
0:21And for those who don't know me, it's a
0:23pleasure: I'm Marcos Vasconcelos. I've
0:25been working with ENEM and college
0:26entrance exams here on YouTube for 4
0:28years.
0:29I've already helped hundreds of students
0:31get into the most competitive medical
0:33schools in Brazil, and I myself have
0:35passed every federal medical school with
0:37my ENEM score.
0:38And man, a major difficulty I had at the
0:41beginning of my preparation was Natural
0:43Sciences. It was the subject I had the
0:46most trouble improving in. I had a very
0:48weak foundation in biology, physics, and
0:49chemistry, especially in physics and
0:51chemistry. I had only gotten 20 out of
0:53the 45 questions right in Natural
0:55Sciences on the ENEM before the one
0:57where I got accepted. Then, after a very
0:59well-executed preparation, focused on
1:01understanding the ENEM test, the test
1:03patterns, and truly mastering the
1:05Natural Sciences content as well, I
1:07managed to get 42 out of 45 questions
1:09right.
1:10I almost aced the test. I went from 20
1:12to 42 out of 45 correct answers.
1:15And here I will pass on all my knowledge
1:17of Natural Sciences, the patterns that
1:19always repeat on the test and are very
1:22likely to show up on this year's exam.
1:25But before we get to the content itself
1:26, I have a request to make of you.
1:29If this video helps you, if you are
1:31positively impacted by the knowledge I
1:33share here today, leave a like,
1:35subscribe to the channel, and leave a
1:38comment. I always see the comments, and
1:40I am extremely happy to know that I am
1:42helping you. I am a full-time medical
1:45student, so the free time I have I
1:46dedicate here to help you, to build
1:48content that will make a difference in
1:51your acceptance, because I was helped a
1:53lot by this type of content when I was
1:55preparing for the test. I prepared
1:57entirely online, and I know the
2:00difficulty you are probably going
2:02through. So leave a like, subscribe to
2:05the channel, and support me with a
2:07comment, as I'm always reading them, and
2:09it really motivates me to keep producing
2:12content. Now in November, we will open
2:14enrollment for the 2026 class of the
2:16Protocolo ENEM platform with the best
2:18Black Friday offer of the year. So stay
2:21tuned and sign up using the link I will
2:23leave here in the description.
2:25The ENEM Protocol Platform is the
2:27complete platform with lessons on all
2:29subjects from the best teachers in
2:31Brazil, my study mentorship, question
2:34pattern lessons teaching content in
2:36practice for you, essay grading by
2:38official ENEM board correctors, Q&A
2:40tutoring, in short, everything to ensure
2:42your approval as quickly as possible.
2:46It's no wonder there were admissions for
2:48Medicine at USP, UFRJ, UFMG, and the
2:50biggest universities in Brazil just this
2:51last year.
2:54So go ahead, click the link in the
2:55description, it will certainly help you
2:56a lot.
2:58Guys, so the first question pattern I
3:00bring to you is a little question
3:01talking about separation of mixtures.
3:04Pause the video, try to solve it, and
3:06now I'll come back with the resolution,
3:08alright?
3:09Paused, tried to solve it, you will
3:10learn much more if you pause and try to
3:12solve it than if you just keep listening
3:13to me talk, okay? So now I come with the
3:16resolution, the reasoning, and a review
3:17of this question pattern that always
3:19appears on the test. What is the stage
3:21for removing a large part of these
3:23solids?
3:24Where does it remove the solids here
3:26from the raw water collected from
3:28reservoirs? So we are talking about
3:30water treatment. What do you need to
3:32know about water treatment for the ENEM
3:34test? Because it appears a lot, really a
3:36lot. And you need to master the most
3:37important concepts, so I'm going to
3:39review them with you here. Take a look,
3:41how does a water treatment plant work?
3:45You'll take the dirty water that will be
3:47here in a reservoir, a river, whatever
3:49it may be, take it to this water
3:50treatment plant, and what is the first
3:52stage that occurs?
3:54It's the flocculation stage. How does
3:57this stage work? Pay attention, how does
3:59flocculation work? You will put the
4:01aluminum sulfate component here. And
4:03then, the dirt, look, this water is
4:05dirty, okay?
4:07So there is the dirt here, you see that
4:08the dirt is kind of spread out, you add
4:09aluminum sulfate, the dirt that was
4:11previously spread out starts to join
4:12together like this, you know?
4:14It starts to aggregate like this, starts
4:16to form flocks, blocks of dirt. So that
4:18dirt that was previously spread out
4:20starts to form several flocks of dirt.
4:22And then these flocks of dirt, right? So
4:24large flocks of dirt, the dirt starts to
4:26join together and turn into several
4:27flocks. What happens after that? This is
4:30the flocculation process. You let the
4:32dirt aggregate, the dirt starts to
4:34aggregate through this, you form flocks
4:36of dirt, okay?
4:38Next is the settling process.
4:41These dirt flakes will begin to
4:43accumulate at the bottom of the
4:45reservoir.
4:47And why is that? Because the settling
4:49process is one of the most common topics
4:50on the Enem exam. Pay close attention.
4:53Settling is the separation of mixtures
4:55based on density.
4:57So, whatever is heavier, whatever is
4:59denser, will accumulate at the bottom,
5:02okay?
5:03So these flakes are denser than water.
5:06What is density? It's mass over volume,
5:09a certain amount of mass over a volume,
5:11you know? So, for example, I have a
5:13marble that weighs 1,000 kg. Man, that's
5:16a very dense marble; you throw it in
5:18water, it's going to sink, get it? So,
5:20for example, I mix water and oil in a
5:23glass. What's going to happen? The oil
5:25will stay on top and the water will stay
5:27at the bottom. Why? Because oil is less
5:30dense than water.
5:32So water has a higher density, a greater
5:33amount of mass over volume, and because
5:35of that, the water accumulates at the
5:36bottom.
5:38And so this mixture separation process
5:41called settling separates by density,
5:43got it?
5:45Density.
5:46So anything that is denser than water
5:49will remain accumulated at the bottom.
5:52So most of these dirt flakes will end up
5:54at the bottom. But there will still be
5:56some small bits of dirt that won't stay
5:58at the bottom of the reservoir and will
6:00continue with the water.
6:02Then comes our next step, the filtration
6:04stage.
6:05How does filtration work? In filtration
6:08, you separate solids from liquids. So,
6:11we have the water, and there will still
6:13be some little bits of dirt in it.
6:15We will use a filter that will hold
6:17these dirt pieces while the water passes
6:19through.
6:20What will this filter be? It will be a
6:22filter made of sand, gravel, and
6:23activated charcoal.
6:25Sand and gravel will hold these dirt
6:27pieces that are still in the water and
6:29let the water pass through.
6:32So the water passes, but the dirt, this
6:33little bit of dirt here, cannot get past
6:35the filter. And the activated charcoal?
6:38Activated charcoal is important to
6:39eliminate any residual taste from the
6:41water.
6:42So it mainly helps with that. It also
6:45helps you remove odors or any organic
6:48impurities, you know? So, activated
6:51charcoal is mainly there for that
6:53purpose, you know?
6:54Uh, sand and gravel will trap those
6:56small particles of dirt that are still
6:59in the water. It passed through the
7:01filter, so the water is much purer now.
7:03But our water treatment process isn't
7:05over yet.
7:07You need to add chlorine and fluoride.
7:09What is the chlorine for, guys?
7:13Chlorine is used to disinfect the water
7:15.
7:17So, chlorine is a bactericide.
7:20It will remove any bacteria still in the
7:22water, any biological organisms still in
7:25the water, precisely so the water
7:27undergoes the disinfection process.
7:30So, for disinfection, you add chlorine
7:32to eliminate any residual living
7:34organisms that were still in the water,
7:36right? So, what about the fluoride? Is
7:39fluoride for that too?
7:40No. In Brazil, there's a recommendation
7:42to add fluoride to the water precisely
7:44to prevent cavities.
7:45So, to take care of dental health. If
7:47you're asked what the fluoride added to
7:49the water is for, it's to prevent
7:51cavities, to look after dental health,
7:52which is why we add it in water
7:54treatment, okay? So, water in Brazil is
7:56fluoridated, alright? Potable water.
7:59Then it comes to the water reservoir,
8:00goes into the tank, and starts spreading
8:01throughout the city.
8:03Did you understand the mixture
8:04separation process? Pause the video, try
8:06to explain it on your own: how it works
8:08, what the function of each stage of
8:10water mixture separation is. It's very
8:12important content, you know? Not just
8:14for the Enem exam, but for life. It's
8:15important for you to know how water
8:16filtration happens, how water treatment
8:18happens, you know? The water that
8:20reaches your house every day.
8:21So try to explain it to yourself, do
8:23this self-explanation, and now we'll
8:25move on to talk about some of the main
8:26mixture separation methods that appear
8:28on the Enem exam.
8:30And I'll have to move my face up here,
8:32just so I don't block you from seeing
8:34everything clearly.
8:36What happens, guys? There are some that
8:38appear more and some mixture separation
8:39methods that appear less.
8:41I'm going to focus here on the ones that
8:43appear most, the ones that are most
8:44important for your test, but if you want
8:46, you can dive deeper into other mixture
8:48separation methods that don't appear as
8:50often. I'll try to post a lesson here on
8:52YouTube this week talking about this,
8:53since it's very important content that
8:54appears every year on the test. Anyway,
8:56I'll focus here and give you a summary
8:58of the main ones you need to know, okay
8:59? So first of all, guys, let's talk
9:03about centrifugation and filtration.
9:06Filtration, man, you use it to separate
9:09solid from liquid, okay? Solid and
9:11liquid. Filtration is solid and liquid,
9:14get it? So it's a heterogeneous mixture
9:16of solid and liquid. That is when you
9:18will use filtration.
9:20You place a filter, right, where the
9:22liquid can pass through, but the solid
9:24will be, will stay held, will will hold
9:26, this filter will hold the solid and
9:28the liquid passes, get it?
9:31So you can remove the solids that are
9:33contained in the liquid in heterogeneous
9:35mixtures.
9:37What is a heterogeneous mixture? It's
9:39that you can still see the solids in
9:41this liquid, get it?
9:43So you can see a difference there, sort
9:45of a phase in this this specific mixture
9:48.
9:49Okay, filtration is very important, okay
9:50?
9:52Filtration is also in water treatment,
9:54it serves to remove those, eh, those few
9:56dirty things that were still in the
9:57water.
9:59The majority was removed by decantation
10:00. Centrifugation. What is centrifugation
10:03, guys? Centrifugation, you separate by
10:05density. So you put it in a centrifuge.
10:07What is a centrifuge? It's a thing that
10:08keeps spinning, spinning, spinning,
10:09spinning, spinning. And then, this thing
10:11keeps spinning, spinning, spinning,
10:12spinning. What happens with it? It makes
10:14the separation by density of the
10:17compounds happen faster, right? So, I'll
10:20give you an example. Blood, blood, blood
10:23test. You put the blood test tube here
10:25in the centrifuge and then it starts to
10:27spin, spin, spin, spin. And then what
10:29happens, guys?
10:31The part with blood cells will stay
10:33lower in the tube.
10:35It will stay lower in the tube. Why?
10:38Because it's heavier, because it's
10:40denser.
10:42While blood plasma, which is water,
10:44mineral salts, anyway, blood plasma will
10:47stay higher up. Why? Because it's less
10:49dense. So what is less dense stays on
10:51top and what is denser stays further eh
10:53stays further down, right?
10:55So it stays further down because it's
10:57heavier, let's say, it's denser, get it
10:59? And it can also eh be done here sort
11:02of horizontally. Then what is denser
11:05will stay in this outer part, okay? So
11:07what is denser will stay in this outer
11:09part.
11:10So, for example, the blood cells will
11:12stay out here and what is less dense
11:13will stay here a little more inward,
11:14which in this case is the blood plasma,
11:15which is water and mineral salts, get it
11:17?
11:18So it separated by density. Did you
11:20understand centrifugation? Important,
11:21okay? It has appeared a few times. And
11:23decantation also separates by density,
11:25it's just that decantation is usually
11:27slower than centrifugation, you see?
11:30And uh decantation can be for
11:31liquid-liquid or it can be for
11:33solid-liquid, as we showed at the water
11:35treatment plant, right?
11:37Now, another very important one that
11:38people don't know. Pay attention. What
11:41is distillation?
11:43With distillation, you are separating
11:45homogeneous mixtures, homogeneous
11:46mixtures, okay?
11:48You perform a physical separation. What
11:50do you mean by homogeneous mixture?
11:52Man, when you take a spoonful of salt,
11:53you throw it in a glass of water and mix
11:55it, you won't be able to see the
11:56difference between the salt and the
11:57water anymore.
11:58So it became a homogeneous mixture,
12:00right? A single-phase mixture, you can't
12:02see any difference.
12:04And so, how do you separate this mixture
12:06that you can't see the difference in?
12:08Man, what you need to do is distillation
12:10. What is distillation?
12:12You will increase the temperature of
12:14this mixture and then, by the different
12:17boiling points.
12:18What is a boiling point? It's the point
12:20at which a liquid turns into a gas.
12:22The point where you have the
12:23transformation of the compound from
12:25liquid to gas.
12:26What happens, for example, with water
12:28and salt?
12:29Water and salt have very different
12:31boiling points, you see?
12:34So, while the boiling point of water is
12:35around 100 degrees, the salt's is
12:37extremely high, much more than that. So
12:39you put, for example, water and salt in
12:42a container, you heat this container up
12:45to 100, 110 degrees. What will happen is
12:47that the water will evaporate and then
12:49it will, uh, it will, there is a
12:50mechanism here for it to end up in
12:52another container and the salt will
12:53accumulate here.
12:55So what did this heating generate? We
12:58managed to separate it, because the salt
13:00will stay here in this container and the
13:01water that evaporated goes to this other
13:03container. So you perform the separation
13:06by the different boiling points, you see
13:09?
13:10By the different temperature points that
13:12exist between the materials. In this
13:14case, salt has a much higher boiling
13:16point than water. And fractional
13:19distillation? Fractional distillation is
13:21when you want to separate several
13:23different substances by their boiling
13:25point. So, for example, petroleum.
13:28Petroleum is a mixture of several
13:29different substances, a homogeneous
13:31mixture, and so you want to separate
13:32each part of the petroleum. You want to
13:34get gasoline, you want to get gas, you
13:36want to get diesel, you want to get
13:37kerosene. Man, all of this is in crude
13:39oil. How do you do it?
13:41You take a fractionation column, a
13:43fractionating tower, you heat the oil,
13:45and then each, each specific place will
13:47have a, a certain boiling point, okay?
13:50So there will be a certain, uh, each
13:52compound will have a certain boiling
13:54point.
13:55And then these compounds are separated
13:56one by one.
13:57So there are also certain columns that
14:00have some liquids that will make these
14:02compounds go back to their phase, they
14:04can, uh, perform there, uh, condensation
14:06, turn these gases back into liquid
14:08again.
14:09And then it performs the separation of
14:11each different compound. The gas, for,
14:13for instance, will stay up here, then
14:15there's gasoline, there's kerosene,
14:16there's diesel, right? And so, through
14:19this difference in boiling points
14:20between the different components, right
14:22, of the oil, you perform their
14:24separation, okay?
14:25In the fractionating tower, right?
14:28So it's a more complex method, a method
14:30you use when you want to separate
14:32several different compounds by boiling
14:34point, okay?
14:36So, did you get that, man? And those are
14:39the main, uh, the main mixture
14:41separations that appear on the test.
14:44There's also magnetic separation that
14:45uses the magnetic properties of the
14:47compounds, there's sieving, right, which
14:49uses the different size between the
14:51compounds, the size of the particles.
14:53So I'll have particles that will pass
14:55through the sieve and others that won't
14:56.
14:57So there are several different types of
14:59mixture separation, but I covered the
15:00main ones here for you, the ones that
15:01really appear on the Enem.
15:03So for this question here, what will be
15:05the answer, guys? The answer will be
15:07decantation. Why decantation?
15:11Because it is in decantation that we
15:12remove most of the solids, a large part
15:14of the solids.
15:16Does filtration remove some solids?
15:19It does, but a large part is in
15:20decantation and it asks exactly for the
15:21one that removes a large part of the
15:23solids.
15:24So you have to pay attention to the
15:25question's instructions. If it included
15:27decantation and filtration and asks
15:29which one removes a large part of the
15:30solids, it's decantation. Isn't
15:32filtration also a solid-liquid
15:34separation process? It is, but it's not
15:36the one that removes a large part of the
15:37solids, understand?
15:39So you had to have this notion of a
15:40water treatment plant to solve this
15:42question easily as well.
15:44You see that there are many solids here
15:45, the flocks accumulate at the bottom
15:47due to the difference in water density.
15:50So, the dirt flakes accumulate at the
15:51bottom in this decantation process.
15:55Now, here's another question; feel free
15:56to pause and try to solve it, okay? Now
15:58I'll provide the solution. Look, it
16:00wants to separate uranium-235 from
16:03uranium-238, right? Uranium-235 from
16:05uranium-238. And, well, considering the
16:08mentioned mass difference between the
16:09two isotopes, what kind of alternative
16:11procedure to effusion can be used for
16:13this purpose? Then it gives the options
16:15here for a mixture separation method.
16:18Guys, mass difference between two
16:20components, two components, right, which
16:22are isotopes, two components that are
16:23the same chemical compound, only having
16:25a difference in mass.
16:27Remember what I said? Density is mass
16:30over volume.
16:33So, look, if their only difference is
16:34mass, if one is uranium-235 and the
16:36other is uranium-238, then one will be
16:37denser than the other.
16:39If we want to separate by density, the
16:41only alternative that speaks to that is
16:44centrifugation. Centrifugation is the
16:46only alternative that separates
16:48compounds by density, right?
16:51Sieving is by particle size, particle
16:53size, okay?
16:55Solvent extraction is by difference in
16:57solubility, which is not mentioned in
16:59the text.
17:00Fractional distillation is for different
17:02boiling points, and there are only two
17:04components, there's no reason to do that
17:07, you know?
17:09Magnetic separation also makes no sense
17:10here because it didn't mention magnetic
17:12properties, okay?
17:14So it cannot be any of these. The only
17:16one that mentions something related to
17:18mass would be centrifugation because it
17:20is a mixture separation by density,
17:22right?
17:23So the only correct answer in this case
17:24is centrifugation. Guys, this is a
17:26subject that appears every year on the
17:28Enem exam; you need to know it, you need
17:30to pay attention, it's a standard
17:31question pattern for mixture separation
17:33on the Enem exam. Now let's go to the
17:35next question pattern. Pause, try to
17:37solve it, and now I'll solve it with you
17:40. Look, this question here is about wave
17:43phenomena, okay?
17:44Let me put it here as wave, which is
17:46easier.
17:47A question on wave phenomena.
17:49Man, what do you need to know to solve a
17:51wave phenomenon question?
17:53You need to know the definitions of the
17:55main wave phenomena. These are easy
17:57questions, standard questions, they
17:59appear on the test every year, and with
18:00the reasoning I'm going to give you
18:02today, you'll be able to solve this type
18:04of question easily.
18:06Before we actually solve this question
18:08here, I'll list for you here what the
18:10main wave phenomena are.
18:12So let's do a quick summary, I won't go
18:14into much detail here, I'll just give
18:15you a summary of what you need to know
18:17to get these types of questions right
18:18regarding the main wave phenomena. Let's
18:20go. First wave phenomenon. The wave
18:22phenomenon of reflection. How does this
18:25wave phenomenon of reflection work?
18:27Think of a mirror, man. You look at your
18:29image in the mirror. And why do you look
18:31at your image in the mirror? Why do you
18:33see your reflection in the mirror?
18:35Because the light that is incident, the
18:37light coming from you, that hits the
18:39mirror, right?
18:40Light hits you, then it reflects off you
18:42and goes to the mirror. What happens is
18:45that when this light reaches the mirror
18:46, it changes direction.
18:48So it reflects back to your eyes. And
18:51that's why you see your reflection.
18:53So the wave phenomenon of reflection is
18:55just the change in the wave's direction
18:58.
18:59It doesn't change any other
19:00characteristic of the wave.
19:02It doesn't change frequency, it doesn't
19:03change wavelength, it doesn't change
19:04speed, none of that.
19:06It just hits the mirror, bounces back,
19:08reaches your eye, and that's why you can
19:09see the reflection. So that is the wave
19:12phenomenon of reflection. All wave
19:14characteristics are preserved. And what
19:16about the wave phenomenon of refraction
19:17? That one is a little more complex. So
19:19let me explain the main characteristics
19:21of waves to you. First of all, let's put
19:24the fundamental wave equation here.
19:26Equation, you don't like equations. Man
19:28, this is the formula that has appeared
19:29the most in the history of the Enem. V
19:31equals lambda F. So pay attention
19:32because I'm going to explain to you very
19:34simply what that means. And so, what
19:36matters for you to know to solve these
19:38theoretical questions? The wave speed
19:40depends on the medium it is propagating
19:42through.
19:43So, for example, the speed of light,
19:45light is a wave.
19:48Light in the air will have a different
19:49speed than it does in water.
19:52So the speed of light in the air is
19:53different from the speed of light in
19:55water.
19:56So air is one medium, water is another
19:58medium.
20:00When light passes from air to water, it
20:02decreases its propagation speed, right?
20:05So speed is not constant for waves, it
20:07depends on the medium. Look, write this
20:09down. Speed depends on the medium in
20:11which the wave is placed. Then we have
20:14the lambda. Lambda is the wavelength. It
20:16will also end up depending on the medium
20:18, because it varies according to the
20:20wave's speed. And what about frequency?
20:22Does the frequency change according to
20:24some change in the wave, or something
20:26like that? No. Frequency only depends on
20:29the source emitting the wave.
20:31So, imagine the following, man.
20:33You're emitting a certain sound wave
20:35with a guitar.
20:37So you played a guitar chord.
20:40Man, the frequency of this chord, of
20:42this wave you played on the guitar, it
20:44will always be the same.
20:46It will always be the same. So the
20:48frequency does not change, okay? The
20:50actual frequency of a wave does not
20:52change.
20:54And in the Doppler effect, the apparent
20:55frequency can change, but that’s another
20:57topic, a more complex one, you know?
20:59But the actual frequency of a wave never
21:01changes, and the Enem has explored this
21:03in many ways over the years. So,
21:05frequency does not change. Speed and
21:08lambda vary according to the medium,
21:10right? Frequency is a characteristic of
21:13the source that is emitting the wave.
21:15So, you have to know this. Check this
21:17out, refraction. What do you need to
21:19know? It is the change of the
21:20propagation medium. If the propagation
21:22medium is changing, what will happen?
21:24What will change? What will change in
21:25the wave if the propagation medium is
21:27changing? The speed and the lambda. So
21:29the wavelength, right? And the speed are
21:32what will change.
21:34So if the wave is passing from air into
21:36water, what will happen?
21:38We will have a change in the direction
21:39of this wave, okay?
21:41So the wave will change its direction,
21:43and besides that, it will alter its
21:45speed and its wavelength.
21:47In air, a light wave propagates much
21:50faster than in water. Water has more
21:53resistance to the passage of light than
21:55air.
21:57And with that, in water, light ends up
21:59moving more slowly, with a lower speed.
22:03So what do you need to know about
22:04refraction? Refraction is when a wave
22:06changes its medium. If it mentions a
22:09change of medium, change from water to
22:11air, from air to water, the phenomenon
22:13of refraction is occurring. A practical
22:16example of refraction for you.
22:18When you take a pencil or a pen, put it
22:20in a glass of water, and then you see,
22:21it looks like the pencil is broken,
22:23right?
22:24That there is a discontinuity in the
22:26pencil. Why does this happen? Because
22:28the phenomenon of refraction is
22:29occurring.
22:31So, the light hits the pencil that is
22:33inside the water, this light is
22:34reflected by the pencil, and then with
22:36this reflection of light that the pencil
22:38makes, what happens is that the wave
22:40will end up changing its direction of
22:42propagation when it goes up, when it
22:44changes from water to air.
22:47And with that, we have a sensation, an
22:49image formed there that makes it look
22:52like the pencil is broken, because the
22:54wave's direction of propagation changed
22:56, you know?
22:58And so it changed the view a bit, the
22:59location where we would see this part of
23:01the pencil that is immersed in the water
23:02.
23:03That is refraction. The wave's speed
23:06changes, the direction of propagation
23:07changes, right? Now diffraction. How
23:10does this wave phenomenon work?
23:12Diffraction is when a wave goes around
23:14objects, when the wave has the ability
23:16to go around objects.
23:18Classic example, you are in your room
23:20and someone arrives at your house, you
23:22can hear the noise of someone arriving,
23:23you hear someone talking in the kitchen
23:25.
23:26Why are you hearing that?
23:27Because sound waves are capable of going
23:30around the objects in your house and
23:32reaching your room.
23:34So, that is diffraction, simply that. It
23:37is when a wave encounters an obstacle
23:39and is able to go around it.
23:41That is simply diffraction, it's one of
23:43the easiest wave phenomena. Don't
23:45confuse it with refraction, okay?
23:47Similar name, but it is not the same
23:49thing.
23:50Refraction is when the medium changes,
23:52okay? Diffraction is only when you are
23:54going around objects, obstacles. Now the
23:56phenomenon of polarization. What would
23:57this phenomenon of polarization be?
23:59It is when you place a filter there for
24:02the wave where only certain wave
24:04frequencies or only certain directions
24:06of wave vibration will be able to pass
24:08through this filter.
24:11So, for example, when we wear sunglasses
24:13, why is it easier for people to drive
24:16when wearing sunglasses on a sunny
24:18highway?
24:21It is because the sun hits the hood of
24:23the car and it is reflected into the
24:24person's eye.
24:27But when the person is wearing glasses,
24:29what happens is that there will be a
24:31vertical filter there, a filter that
24:33will only let beams of light pass
24:34through vertically.
24:38With that, that light being reflected
24:39off the car's hood, being reflected off
24:41the road, it is coming in horizontally,
24:43man.
24:44And this light cannot pass through those
24:47vertical filters. The vertical filters
24:50will only let light waves pass through
24:53vertically.
24:54And with that, you reduce the intensity
24:57of light reaching a person's eye, so you
24:59can see better on the road, see better
25:01on beaches too, because the light ends
25:03up reflecting off the sand and comes
25:05back to your eye as horizontal light.
25:08And when you have glasses with a
25:10vertical filter, you block that
25:11horizontal light and only receive the
25:13vertical light, so it’s much easier to
25:15see and puts much less strain on your
25:17eyes, okay?
25:18Another classic example: 3D glasses. How
25:21do 3D glasses work? You have light
25:23filters here, let me change the color.
25:25You have light filters on each side,
25:27right? You have filters here on these
25:29glasses.
25:30And one of the lenses has a vertical
25:32filter and the other has a horizontal
25:34filter, right?
25:35So, lying flat. And what happens because
25:37of that? You don't let certain wave
25:40propagation directions pass through. So
25:42, here in the left eye, you would only
25:44receive vertical waves, so it only lets
25:47vertical waves pass, and here in the
25:49right eye, only horizontal waves.
25:51This ends up creating a
25:52three-dimensional effect in our brain
25:55when it interprets the image coming into
25:57these eyes. That’s why you end up seeing
26:00in 3D.
26:01That is the characteristic of 3D glasses
26:03; they use filters so that you
26:04experience this phenomenon of seeing in
26:06three dimensions when you're watching a
26:08movie, the image in a three-dimensional
26:10way.
26:12Now for another wave phenomenon, one of
26:13the most frequently asked about on the
26:15exam, which is the phenomenon of
26:16interference. Interference is basically
26:18when you add two waves, okay? You are
26:20adding two waves together.
26:22There is constructive interference,
26:24where this sum results in a wave with a
26:26larger amplitude, therefore a wave with
26:28greater intensity, right?
26:31So, for example, I place two speakers
26:33here, man. I’m receiving the sound from
26:35these two speakers. But the sound waves
26:37from these speakers will end up crossing
26:38each other along the way. What will
26:41happen to these sound waves when they
26:43meet? I play the same music through both
26:44speakers. What will happen is that the
26:46volume of the music will get louder. So
26:49I will hear it better. Why? Because we
26:51are having an overlap of these waves. So
26:53the wave from each speaker adds up and
26:56becomes a much larger wave. And with
26:58that, you end up hearing a higher volume
26:59. In destructive interference, what
27:01happens is that these are waves in
27:03opposite phases.
27:05And when these waves, right, in opposite
27:07phases join together, they will reduce
27:09their intensity.
27:10So one will cancel the other out, one
27:12will reduce the intensity of the other,
27:14precisely because they are in opposite
27:16phases. Look, the phase here is
27:18different in this case.
27:20They are not the same wave; they are in
27:22opposite phases.
27:23And that is exactly the technology
27:24behind noise-canceling headphones. It
27:26has a microphone that listens to the
27:28external sound, the ambient sound.
27:30This sound will be processed; there is a
27:31processor in these headphones that will
27:33handle this sound. And it will generate
27:35a sound that is in the opposite phase to
27:37that sound coming from outside, to that
27:38sound you are hearing on the street, in
27:40the environment you are in. And then
27:42this sound in the opposite phase will
27:44add up, right, with this sound coming
27:46from the street. And with that, we end
27:48up having a smaller wave, a wave with
27:50smaller amplitude.
27:52When we have the sum of those two, right
27:54, which are in different phases, what
27:56happens is that they will reduce their
27:58intensity. So they will decrease their
28:01intensity, right? So precisely because
28:03they are sounds in different phases. The
28:05processor will generate a sound in a
28:07different phase from the one you are
28:09hearing from the external environment.
28:11It will project it into your ear, and
28:13then the sound coming from outside will
28:14end up canceling itself out with this
28:16sound that the noise-canceling
28:17headphones are generating.
28:19And the phenomenon of resonance, how
28:21does it work? Guys, the resonance
28:23phenomenon is one of the most
28:24interesting ones. Every material, what
28:26do you need to know?
28:28Every material has a specific natural
28:29frequency of vibration, you know?
28:32So it is important that you know this.
28:33Everything has a certain natural
28:35frequency of vibration.
28:36And so, when this material that has a
28:38natural frequency of vibration receives
28:41a certain sound at the same frequency as
28:43its natural vibration, when it receives
28:45a certain wave that comes at the same
28:47frequency as its natural vibration, what
28:49happens is that there is a transfer of
28:52energy from this wave to this material.
28:54So the energy keeps accumulating.
28:57A classic example of this, guys, is when
28:59you must have seen in movies that some
29:01people start singing, start screaming,
29:03and then the wine glass, the glass cup
29:04ends up breaking.
29:06Why does that happen? This is a real
29:08phenomenon.
29:09The sound that is being emitted by the
29:11person ends up coming at the same
29:13frequency as that glass material.
29:15And so, with that, the energy coming
29:17from the sound, from the noise being
29:19emitted by that person, ends up being
29:21transferred to this material, and this
29:23material ends up cracking, ends up
29:24breaking.
29:26Another classic example, there was a
29:28bridge in the United States, right, that
29:29was built in the last century, I don't
29:31remember the exact name of the bridge,
29:33then a gust of wind came that, well,
29:34wasn't a strong enough gust to knock the
29:36bridge down, to make the bridge's
29:37structure yield, but this gust of wind
29:39was at the same frequency as the natural
29:41vibration of that bridge.
29:44And so, with that, what happened was
29:46that this bridge ended up collapsing,
29:48because we had the transfer of energy
29:49from this wind, from this gust of wind
29:51to the bridge, and the structure yielded
29:53.
29:55They didn't foresee this resonance
29:56phenomenon, the engineering wasn't done
29:58to prevent this kind of thing, right, in
30:00this specific case.
30:02In other bridge cases, they already have
30:04a protection mechanism for the resonance
30:05phenomenon, largely because of this
30:07episode, actually.
30:09And so, with that, the bridge ended up
30:10yielding, because there was this very
30:12large transfer of energy.
30:13Resonance is just that, you know?
30:15Magnetic resonance is also a medical
30:17exam that uses this wave phenomenon of
30:19resonance.
30:21So, they emit certain sound wave
30:23frequencies that end up vibrating at the
30:25same vibration as the atoms of the
30:27protons there in certain materials.
30:31And then these protons end up emitting
30:32back a certain vibration as well, which
30:34is interpreted by the exam.
30:36So that's basically how magnetic
30:38resonance works. Guys, wave phenomena
30:40are very interesting, okay?
30:42And I made a great summary with
30:44everything you need to know to get any
30:46question on wave phenomena that might
30:47show up on the test right, okay?
30:49There's a complete class on wave
30:51phenomena here, on waves on my channel,
30:53with everything about waves for the Enem
30:54.
30:55If you want to watch it, it's really
30:56worth it, as it's one of the subjects
30:58that shows up the most in the physics
30:59section, so if you study it well, it's a
31:00guaranteed hit. But I managed to
31:02summarize the main ones, the ones that
31:04show up most in wave phenomena here. So
31:06, you can already solve this question
31:07easily. So, what is the technology
31:09behind noise-canceling headphones? It's
31:11precisely interference, destructive
31:13interference, right? So, the
31:15noise-canceling headphone will take the
31:17sound coming from the street, coming
31:18from the external environment, and
31:20generate a sound in the opposite phase
31:21to this sound coming from the outside.
31:24And so, when these sounds meet, the
31:25sound from the street and this sound the
31:26headphones are generating, they end up
31:28canceling each other out.
31:29And so, with that, you have the
31:31cancellation of external noise. Marcos,
31:32what about absorption? You didn't talk
31:34about absorption, couldn't it be
31:35absorption? Absorption, basically, is
31:37when a certain material, when a certain
31:39medium absorbs the wave's energy.
31:42It's usually absorbed as heat, which
31:44isn't the case for noise-canceling
31:45headphones, right? So, the sound coming
31:47from the street there decreases because
31:49it's generating a frequency in opposite
31:51phase, it's generating a wave in
31:52opposite phase.
31:54What would be a classic example related
31:56to absorption?
31:59Have you ever seen those construction
32:00earmuffs you wear so you don't hear so
32:02much noise from the site, that PPE,
32:03personal protective equipment that
32:05construction workers use, that kind of
32:07thing?
32:08Man, why do they use that, right?
32:10Because this equipment works based on
32:12the phenomena of reflection and
32:14absorption.
32:16So, the sound that reaches this
32:17equipment ends up being reflected, and
32:19what is absorbed will have a foam-like
32:21material that prevents it from reaching
32:22the eardrum, the ears, the person's
32:24hearing.
32:25And with that, this person won't hear
32:28that noise coming from outside. So, when
32:31it's those earplugs, right, those used
32:33on construction sites, that workers use
32:35, it's the phenomenon of absorption and
32:37reflection at work that prevents that
32:40sound from reaching people's ears and
32:42damaging their hearing. When you are
32:44exposed to loud noises for a long time,
32:47you end up damaging your hearing.
32:49So it's important for people who work in
32:51construction to use this equipment,
32:52right?
32:53Now another example, right? If you want
32:55, pause and solve it. Basically, what is
32:57he talking about here? The phenomenon of
32:58Fata Morgana. And he explains that,
33:00right?
33:02That light is reflected by the cold
33:04water and is bent by an unusual layer of
33:06warm air above, reaching the observer
33:08from many different angles.
33:11Then he talks about the Titanic case,
33:13right?
33:14That the Titanic, the captain might not
33:16have seen the iceberg because of this
33:18Fata Morgana phenomenon, as the iceberg
33:21might have appeared further away, or
33:23might not have appeared in his sight
33:25precisely because of this Fata Morgana
33:27effect where light changes its
33:29propagation medium.
33:31So it was coming from the water, right?
33:35It comes from the water and then it
33:37moves into warm air, then there's the
33:38cold air, right?
33:40And with that, you end up generating a
33:42phenomenon where you have a change in
33:44the wave's propagation medium.
33:46If there's a change in the wave's
33:48propagation medium, you have a change in
33:50the wave's direction of propagation and
33:52its speed.
33:53And with the change in the wave's
33:55direction of propagation, what happens
33:57is that the observer won't see the
33:59object in its actual position.
34:02In this case, the observer, the ship's
34:04captain or pilot, may not have seen the
34:07iceberg in its exact position, which led
34:10to the Titanic colliding with it.
34:13So the answer in this case is letter B,
34:15refraction.
34:16This is the phenomenon involved due to
34:18the change in medium, the change in the
34:20direction of wave propagation, meaning
34:22he won't be able to see exactly where
34:24the iceberg is, heading right into it
34:26and colliding.
34:28Folks, wave theory questions are always
34:29like this; they give you a context and
34:31ask what wave phenomenon is involved.
34:33This type of question appears every year
34:34.
34:35I covered the main wave phenomena, the
34:37ones that really show up on the test,
34:39here in this lesson.
34:41But there is a complete lesson on wave
34:42theory here with everything you need for
34:43the ENEM. If you want to watch it, it's
34:45really worth it.
34:46Professor Isaac, our physics master from
34:48the protocol, also covers other types of
34:50wave content that might appear on the
34:52exam.
34:53It’s worth taking a look. Now, let's
34:55move on to the next question pattern.
34:57This one is a classic that will surely
34:59be on your exam on Sunday. So, pause and
35:01try to solve it.
35:03This question pattern deals with organic
35:05functional groups, okay?
35:07So, it's an organic chemistry question
35:08pattern. Basically, what do you need?
35:11You need to identify the organic
35:13functional groups present in the
35:15compounds.
35:17In this specific case, it asks which one
35:19is common, meaning it's in both
35:20compounds.
35:22You would need to know that this C
35:24double bond O OH is a carboxylic acid,
35:27right?
35:29That it's present here in compound one,
35:31and you would need to know that this C
35:33double bond O OH is also a carboxylic
35:35acid present here in compound two.
35:37Besides that, in this compound two, we
35:39also have a ketone, right?
35:41Where we have it bonded to two carbons
35:42with a double bond O in the middle, and
35:44we also have a phenol.
35:46In this case, man, it's all about
35:48knowing your organic functional groups.
35:49I'm going to explain organic functional
35:51groups to you quickly, okay?
35:53The ones that usually show up on the
35:54test, but it's good for you to print out
35:56a little sheet with the main organic
35:57groups and review it every day before
35:58the test, because, man, they show up a
36:00lot.
36:01I would say carboxylic acid, alcohol,
36:03ether, and ester are the ones that
36:05appear the most.
36:07But honestly, it's good to know them all
36:08, because any one of them can show up,
36:09and questions about organic functional
36:11groups appear every year. If you know
36:12them, if you have the organic functional
36:14groups memorized, you can already get
36:15that question right, okay? So, I'll talk
36:17to you about them quickly, okay? Organic
36:19functional groups. So, they would be
36:21certain compounds that are present in
36:23hydrocarbon chains. Alright, so let's go
36:25. The main organic functional groups you
36:27need to know. First of all, an alcohol
36:29is a C bonded to an OH.
36:31So, in carbon chains, what you'll have
36:33is exactly this here.
36:36Look at this.
36:37Here we have an alcohol.
36:39We have an alcohol. Why? Marcos, but
36:41there's no carbon here. Yes there is,
36:42man. There is a carbon here. It's just
36:44that they represent them, the
36:46representation of carbons, these carbon
36:48chains, is just little lines, right?
36:49Because since they are carbon chains,
36:51it's more simplified to represent them
36:52like this, and on the ENEM they only
36:54represent them this way, okay? So here,
36:56even though it's not indicated, there is
36:58a carbon.
36:59So it's a carbon bonded to an OH, and
37:02it's also bonded here to two hydrogens,
37:04so hydrogens that are hidden here,
37:06because it needs four bonds to be stable
37:08.
37:09So here you have a carbon bonded to an
37:11OH.
37:13Whenever there is a carbon bonded to an
37:14OH, you should think of alcohol, the
37:16alcohol function.
37:18We also have the ketone, which was
37:20present here in this compound we saw,
37:23which is a C bonded to a C bonded to two
37:25carbons and an oxygen, right?
37:29So for ketone, remember C ketone, the
37:31one in the middle is a C with a double
37:33bond to O. Remember ketone, there's a C
37:35here and an O here, right?
37:38And then the C bonded to an O here in
37:40the middle, right? I can remember it
37:42easily. Ketone is the one in the middle
37:44, it's the carbon with a double bond to
37:45O in the middle. Oh, it fell down here.
37:47Let me pick it up.
37:50Right here. So it has to be bonded to
37:52two carbons and have a double bond to O
37:53in the middle, got it?
37:55Phenol, phenol is very easy to identify
37:57. It's the one I showed here. It's just
37:59a benzene ring here that's bonded to an
38:02OH. So, in this case, we have a phenol.
38:04Ether, ether is when you have a carbon,
38:06right, when you have an oxygen in
38:07between the carbons, right?
38:09So, for example, how would this be
38:11represented on the test? This one comes
38:12up a lot, okay? Ether would be
38:14represented this way. Here we have an
38:16ether, okay?
38:18Which is bonded to an O linked to two
38:20carbons, it's between two carbons.
38:22This right here is an ether.
38:24We have the enol, right, which is when
38:25we have a double bond there between the
38:27carbons.
38:28So, an example for you, okay?
38:31Of an enol, we would have a double bond
38:33linked to the carbons here, right?
38:36And then this middle carbon would bond
38:38to an OH, right?
38:39So this right here would be an enol,
38:42right?
38:44We have a double bond here, the carbon
38:46bonded to the OH, okay?
38:48This would be the enol, it doesn't show
38:50up that much on the test.
38:51The ester, however, shows up very
38:53frequently, okay? So you have to know it
38:55.
38:56Take a look also at the esterification
38:57reaction, which is where we will have
38:59here, look, how this would be
39:00represented in practice.
39:02Pay attention.
39:04It's a carbon bonded to an oxygen that's
39:05also forming a double bond with another
39:07oxygen, understand?
39:09So, in this case here we have an ester,
39:11okay?
39:12This right here would be an ester, got
39:14it?
39:15We also have the carboxylic acid, which
39:16is the one I showed, which I would say
39:17is the one that appears the most, right
39:19? Which is when you have a C double bond
39:21O linked to an OH. So here, for example
39:23, C double bond O also linked to an H.
39:26This right here would be a carboxylic
39:28acid, right? So we have a carboxylic
39:31acid here.
39:32Hydrogen alone will never appear in the
39:34carbon chain, okay?
39:36Amine, how would amines be represented,
39:38right? They usually look like this, look
39:41.
39:41It would be an NH2 here.
39:45So when you see this NH2 alone bonded to
39:47a carbon, think of an amine. Aldehyde,
39:50how would that be, guys? It would be
39:52more or less like this, right?
39:54You would have a carbon here making a
39:55double bond to O and then you would have
39:57an H here.
39:58It would necessarily need to be a
40:00terminal carbon, that is, at the end of
40:02the chain. It would have to be a carbon
40:04here that is at the end of the chain,
40:06okay? Unlike a ketone, which has to be a
40:08carbon that is in the middle of the
40:10chain, since it needs to be bonded to
40:12other carbons, right?
40:14So, it's a carbon at the end of the
40:16chain here, connected by a double bond
40:18to the oxygen, right?
40:20And the amide is also a very interesting
40:22organic compound; you would have, look,
40:25a double-bonded oxygen connected, for
40:27example, to an NH2, right?
40:29And in this case, what do you have here
40:31? You have an amide. This one here is an
40:34amide.
40:35Amide.
40:37This one here is an amine. What is the
40:39difference between an amide and an amine
40:40? It’s that the amide will have an
40:42oxygen along with it. The amine will
40:45just be the nitrogen, okay? So it will
40:47just be the NH2. In the case of the
40:49amide, you will also have a double bond
40:51with the carbon's oxygen. Guys, there’s
40:52no way around it, you have to memorize
40:54it, you know? So what do I recommend to
40:55you?
40:56Print it out, keep looking at it, put it
40:58by your bed, check it every day, because
40:59you’ll get one more question right if
41:01you know these organic functions, okay?
41:03I’ll try to bring an organic function
41:05lesson here to the channel to help you
41:07with a summary of everything you need to
41:08know about organic chemistry to get any
41:10question right on the ENEM. And let me
41:12know in the comments if that would be of
41:13interest to you. Look here, guys, what
41:16is the organic function corresponding to
41:17the functional group present in these
41:19compounds? It’s what I said, we can see
41:21here a C double-bonded to O and
41:23connected to an OH.
41:25So with that, we have a carboxylic acid
41:27here, we have a phenol here, here we
41:29have a ketone, and here we have another
41:31carboxylic acid. Then you say, "Ah Marco
41:33, but how would I know?" Man, this form
41:35isn't broken down, but it’s obvious that
41:37it’s a carboxylic acid. Look, C
41:39double-bonded to O and an OH. These are
41:40the components of a carboxylic acid. So
41:42letter A, the answer is carboxylic acid
41:44, because we have a carboxylic acid here
41:46in compound one and a carboxylic acid in
41:48compound two. Now this one. Want to
41:50pause? Want to try solving it? Try to
41:51solve it. Now I’ll come with the
41:53solution. It says here that it needs an
41:56ester group, right?
41:58Which monomeric unit represents the
41:59polymer best assimilated by
42:01microorganisms? So it wants to know
42:03which polymer contains an ester. Among
42:05these here, which one contains an ester
42:08? Let’s see what the organic function of
42:10each one is. In this case, we have a
42:12simple chain, so here we have a
42:14hydrocarbon, okay? Here is a normal
42:16hydrocarbon, alright?
42:20Here in this B, what do we have?
42:22C double bond O bonded to another oxygen
42:25. What does that mean? Ester. This here
42:28is an ester, okay? This is an ester, C
42:30double bond O bonded to an oxygen. Here
42:32in this third one, we have a nitrogen
42:34bonded to the carbon with a double bond
42:35O. What is this, guys? Nitrogenous
42:37function is an amide, because it has the
42:39double bond O here. In this case, it's
42:42an amide. And you might say, oh Marco,
42:43but you showed it with NH2 there in your
42:45example. But guys, what happens? Amides
42:47can be primary, secondary, or tertiary.
42:51The tertiary one is the one that has no
42:53hydrogen bonded to the amide, which is
42:54this case here.
42:55The secondary one is the one that only
42:57has one hydrogen bonded to the amide, so
42:59it would be something like this, up to
43:01here, an NH, then it would be a double
43:03bond O here too.
43:04And there is the primary amide, which in
43:06this case is NH2, which is the one I
43:08showed you here, okay?
43:10So we would have this case here as being
43:13a primary amide and this case here,
43:15right, being a tertiary amide, okay?
43:18Because the nitrogen is alone in this
43:20case.
43:20You don't need to know much about this,
43:22okay? It's not on the exam, it's just an
43:24explanation for you to have.
43:25In this case here, where we have an
43:27oxygen kind of alone here, what do we
43:29have? We have an ether.
43:31The ether is when you have this oxygen
43:33in the middle kind of alone, right?
43:35So the ether is that, the oxygen alone
43:36in the middle of the chain.
43:38The ester, on the other hand, is the
43:40carbon bonded to an oxygen and also
43:42bonded to another oxygen.
43:44So there is a bonded carbon, there are
43:46two oxygens in the ester, while in the
43:47ether there is only one, okay? And here
43:50we have chlorine, it's not any specific
43:51organic function that is usually asked
43:53on the Enem. So our answer is ester. It
43:57wants the one that has the ester group,
43:59letter B is the one that contains the
44:01ester group. Guys, very easy questions,
44:04you just need to memorize this part of
44:06organic functions to be able to solve it
44:08.
44:09It's worth it, I will try to post a
44:10class with everything about organic
44:11functions, with everything about organic
44:13chemistry for you, I'm sure it will help
44:14a lot, as it is the content that appears
44:16most in chemistry on the exam.
44:18Let's go, guys, biology question now,
44:19pause, try to solve it because this is a
44:21standard question that repeats every
44:23year on the exam.
44:24It asks, the ecological interaction can
44:27be classified as?
44:29So you look at these alternatives, and
44:31it’s immediately obvious that this is an
44:33ecology question about ecological
44:34relationships, which has appeared dozens
44:36of times on the Enem exam.
44:39You need to know the meaning of
44:40ecological relationships, what they
44:42actually mean in practice, and then you
44:43can solve this type of question easily,
44:45with peace of mind, okay?
44:48And I'm going to explain to you here
44:49quickly, give you a little summary of
44:51the main functions of the main
44:52ecological relationships that you need
44:54to know, okay?
44:55Let's start with intraspecific ones.
44:58What are intraspecific, intraspecific
45:00relationships? Look, intra means inside
45:02. Intraspecific, within the same species
45:05.
45:06What is interspecific? Inter is outside
45:08. So, between different species, got it
45:11? So, intra is inside, same species.
45:14Let's look at the main ones here.
45:15Competition is an ecological
45:17relationship between individuals of the
45:20same species where both end up being
45:22harmed in the relationship, and in this
45:25relationship, they are competing for
45:27resources, food, territory, or mates. So
45:30, for example, we have a lion, right, we
45:33have two lions, they start fighting for
45:35territory to see which one will be the
45:37dominant one in that territory. In this
45:39case, we have a dispute between
45:41individuals of the same species, between
45:43lions, so it is characterized as
45:44competition. Why do both end up harmed?
45:47Because both spend energy, both have
45:50risks involved.
45:52So, the species as a whole, or in this
45:54case, the two lions, end up being harmed
45:56in this type of competition relationship
45:59between individuals of the same species
46:00, right?
46:02Cannibalism, man, it’s self-explanatory
46:04. It's when one individual of a species
46:06eats another individual of the same
46:07species, right?
46:08So, there are some famous cannibals in
46:10human history. I won't remember their
46:12names off the top of my head, but there
46:14are some series that talk about people
46:16who are cannibals, who are people that
46:17eat other people.
46:18But there are animals that do this as a
46:20norm, so it’s common for them, such as,
46:22for example, spiders and some insects,
46:23right?
46:24So, for them, it's normal to practice
46:26cannibalism, right? Now speaking about
46:29other types of ecological relationships
46:31.
46:32Harmonious ecological relationships that
46:34are good for all individuals of the
46:36species would be societies where you
46:38have a division of labor. So, for
46:40example, a beehive that has bees. The
46:42bees, they divide themselves into queen
46:45bee, drone, and worker bee.
46:47And then with this division of labor
46:49between the individuals in the hive,
46:52they end up benefiting, they manage to
46:54form a society, they manage to live
46:56better, and prolong the species.
46:59So, in a harmonic relationship, everyone
47:01comes out winning, get it?
47:02Termites also form societies, it's
47:04important for you to know that. And they
47:06are physically separated, okay?
47:09Different from colonies where you also
47:11have a division of labor, only they are
47:13physically joined.
47:14Like some corals, right?
47:16So different corals end up physically
47:18joined, forming those coral reefs.
47:21And so the big difference between a
47:23colony and a society is that within the
47:26colony the animals are physically joined
47:29, okay?
47:31The animals involved, the species
47:33involved, right?
47:35So it's important for you to know that
47:37too. Now let's move on to interspecific
47:39ecological relationships, which are
47:41between different species.
47:43The first one, let's continue here with
47:45the harmonic ones.
47:47We have protocooperation or facultative
47:49mutualism, they are synonyms,
47:51protocooperation and facultative
47:54mutualism, where you don't require the
47:56permanent presence of the individuals.
48:01So look, these are two different species
48:02that end up helping each other, okay?
48:05But they don't depend, their lives don't
48:07necessarily depend on one another. That
48:10is facultative mutualism.
48:12If you see two species helping each
48:14other and both are benefiting, both have
48:17some benefit involved, it's facultative
48:19mutualism, it's protocooperation.
48:21There is also obligatory mutualism,
48:24right? Where there is an exchange of
48:26benefits between different species, but
48:29one depends on the other. So they cannot
48:32survive separated. A classic example,
48:34right? Are lichens.
48:37Lichens are units formed by algae and
48:39fungi where the fungus provides
48:42protection for the alga so that it can
48:44survive, and the alga performs
48:46photosynthesis, generating food that
48:49will help the fungus survive.
48:52So in this case, there is a relationship
48:55where one depends on the other. The alga
48:58depends on the fungus for the existence
49:00of this complex called a lichen, okay?
49:03So one cannot live without the other; in
49:05this case, it's an obligatory mutualism
49:07.
49:08Another classic example is commensalism
49:10, which has appeared many, many times on
49:12the Enem exam, where one of the
49:14individuals, one of the species,
49:15benefits and for the other it's neutral
49:17, it makes no difference if that species
49:19exists or not.
49:21A classic example, a classic example is
49:23when we have the shark and there are the
49:25remoras. The remoras feed on the
49:28leftover food that the shark eats. And
49:31for the shark, it makes no difference at
49:33all to have the remora near it, because
49:34it would be food scraps that it wouldn't
49:36use anyway. The remora ends up
49:38benefiting and for the shark it's
49:40neutral, it's not harmed by this.
49:42There is also inquilinism, which is a
49:44specific type of commensalism where one
49:46species ends up benefiting while it's
49:49neutral for the other, right?
49:51So, in this case, it's when one species
49:54ends up living inside another without
49:56causing any damage, being neutral to the
49:59other species 'existence, right? So,
50:02when there is this type of dwelling by
50:04one species with another, where one is
50:07not harmed by it and the one living
50:09there ends up benefiting, we have a
50:12classic example of inquilinism, okay?
50:14Now, other very important ecological
50:16relationships. Predation, man, it's
50:18self-explanatory, right?
50:20So predation involves different species
50:22where one species preys on, or eats, the
50:25other, right?
50:26So, I'll give you an example: the lion
50:28and the buffalo, right?
50:29So, there are buffalo in the lion's
50:31territory; the lion will hunt them, prey
50:33on these buffalo, feed on them, and
50:35that's predation, and man, that one is
50:37pretty straightforward and
50:38self-explanatory.
50:40Parasitism is when an organism from one
50:43species lives inside another organism or
50:47lives on its exterior and feeds on
50:49fluids or in some way feeds off this
50:52other species, the species it is
50:55parasitizing.
50:57A classic example: lice, right? So, when
50:59you have lice on your head, what happens
51:01is that the louse feeds on your blood.
51:04You're losing blood to the louse, right
51:06? And it's beneficial for it, because
51:08it's feeding off you, right?
51:11Another classic example is the tapeworm
51:12, which you get from eating undercooked
51:14meat; it goes into your intestine and
51:16starts feeding on you, starts
51:17multiplying in there, you know?
51:19Laying eggs.
51:21So, that is also a classic example of
51:23parasitism, right?
51:25Competition, what would that be? It
51:27would be two different species competing
51:30for resources. For example, wolves and
51:32hyenas, right? So, they are in a certain
51:34region, they feed on something similar,
51:37they are fighting for territory; you
51:39have competition between the wolf and
51:41the hyena, a classic example of
51:43competition, okay? Different species in
51:46this case. Amensalism, what would
51:48amensalism be? It's when a certain
51:51organism harms another unintentionally,
51:53without any benefit from it, right?
51:57So, a classic example people mention is
51:59red algae; red algae produce a toxin and
52:01end up killing certain animals that are
52:03around them, but they don't gain
52:05anything from it, you know?
52:09So it's a neutral thing for them to
52:10produce this toxin, but the animals that
52:12end up poisoned by this toxin end up
52:14being harmed.
52:15Now that we've already reviewed the main
52:18ecological relationships in a practical
52:20way, let's see what ecological
52:21relationship is in this specific
52:23question, right?
52:25So it's saying here, some orchid species
52:28have flowers that mimic female wasps, so
52:31that male wasps are attracted in an
52:33attempt to mate.
52:35So flowers mimic female wasps that
52:38attract male wasps, okay?
52:41Upon arriving at the flowers, the males
52:43often come into contact with the
52:44flower's pollen, without any harm to
52:46their activities.
52:49However, since they cannot mate, these
52:51males look for new females, and may find
52:53new flowers and pollinate them.
52:56So what happens, right?
52:59This male, this male wasp, it will find
53:00a certain flower there that is
53:02pretending to be a female wasp.
53:05When it finds, when it finds this flower
53:07, it grabs it, it touches this flower,
53:09it ends up getting impregnated with the
53:11pollen from this flower.
53:13And then, when it goes to find, goes to
53:15look for a female wasp again, there's a
53:16chance it will find another flower again
53:18.
53:20Then it takes this pollen that it was
53:21impregnated with from another flower,
53:22from that first flower I mentioned, to
53:23this other flower.
53:25And so, with that, it ends up
53:27pollinating, performing the pollination
53:29of these flowers.
53:31So, even if it's not his intention, the
53:33flowers, they end up benefiting from
53:34this.
53:36They end up benefiting by having
53:37pollination, generating genetic variety
53:39, you know?
53:41And it's precisely this mechanism of
53:43them mimicking the female wasp that
53:45makes this pollination possible.
53:47And so, what is this ecological
53:49interaction, guys?
53:51Is it good for the for the for the for
53:53the male wasp? Is this ecological
53:55relationship good?
53:56No, it's not good. Is this ecological
53:58relationship bad? No, it's not bad. So,
54:00it's an ecological relationship that is
54:02neutral. It is neutral for the male wasp
54:05. And now, for the flowers, is it good
54:07or bad to have the pollination of the
54:08flowers, right? It's going to be
54:10something good. So, in this case, man,
54:11it has to be an alternative that talks
54:13about something that is neutral and
54:14something that is good. What is the only
54:16ecological relationship among these
54:18alternatives that mentions this? It's
54:20commensalism, right? Remember the
54:23example of the sharks in which the
54:25remoras, they follow the sharks, right,
54:27eating the leftover food from these
54:29sharks that they release there. But for
54:31them, it makes no difference. For the
54:33male wasp, it also doesn't make a
54:34difference if it finds a flower thinking
54:37it's a female wasp, you know? That
54:39doesn't directly harm it. So, it's
54:42something neutral for it and something
54:43good for the flower. So, the answer is
54:45commensalism, right? Now, another
54:47example if you want to solve it. And now
54:50I'll come back with the solution. It's
54:51asking for the ecological relationship
54:53between the mentioned insects. Let's see
54:55here. The carpenter bee, Xylocopa sp. ,
54:59is the most efficient pollinator of the
55:01passion fruit plant because of its size
55:03. The European bee, Apis mellifera, is
55:06not an efficient pollinator of the
55:08passion fruit plant, as it collects
55:09pollen without fertilizing it, and its
55:11small size does not allow it to reach
55:13the flower's stigma due to the distance
55:15from the landing base. Okay. The
55:18ecological relationship between the
55:20mentioned insects, so in this case
55:21between the two bees, what is it?
55:24What is the ecological relationship
55:26between the carpenter bee and the
55:28European bee?
55:29Guys, can you see that they are two
55:31different species? He didn't put this
55:33here for no reason; they are two
55:34different species. So, what kind of
55:36relationship is it? Intraspecific or
55:38interspecific? An interspecific
55:40relationship, between species. You can
55:42see that both perform pollination of the
55:44passion fruit plant, right?
55:47One of them isn't very efficient, it's
55:48not an efficient pollinator, which is
55:50the European bee, but it still performs
55:52pollination of the passion fruit plant
55:53anyway.
55:55What is the ecological relationship that
55:57exists between them? Let's look at the
55:59options here. First option, predation.
56:01Do you think that predation is what's
56:02happening there? That one bee is hunting
56:04the other? That one species of bee ends
56:07up, uh, wanting to eat the other? Man,
56:09that's not what's happening. Remember
56:10that predation involves a predator, and
56:12there's nothing said about a predator in
56:13this text. So the answer can't be that.
56:16Mutualism. Mutualism, the two species
56:18help each other, right? So, uh, did it
56:20say at any point in the text that these
56:22two bees are helping each other? No. At
56:24no point does it make that clear. So
56:26it's not mutualism. Mutualism is when
56:28it's beneficial for both species. It can
56:30be obligatory, where one cannot survive
56:32without the other, or facultative, where
56:34both can survive separately, like
56:36protocooperation.
56:37But it doesn't talk at any point about
56:39that, about the bees helping each other
56:40. Competition. Guys, competition makes
56:42perfect sense there. Why? Because these
56:45two species of bees, both of them end up
56:47competing for the passion fruit plant,
56:49right?
56:51Even though the European bee doesn't
56:53pollinate efficiently, which ends up
56:55being bad for the passion fruit plant,
56:57it is still important for it to seek out
57:00the plant to get its nectar, you know?
57:04So, both end up competing for the
57:06passion fruit nectar; this phenomenon
57:08where it approaches and tries to collect
57:11pollen and such is very much related to
57:13competition.
57:15So, two species that are there
57:17pollinating the passion fruit plant are
57:20in competition with each other.
57:22Let's see if the others make sense.
57:24Inquilinism, guys. Does inquilinism make
57:26any sense? Is anyone living inside
57:28anyone else there? There isn't. So it
57:29can't be that one. Commensalism. What
57:32would commensalism be? It’s what we saw
57:34in the last question, where it's neutral
57:36for one species and beneficial for the
57:38other.
57:39In this case, man, there's nothing
57:41saying it's positive for one and neutral
57:42for the other in the text the question
57:44provided, right?
57:46We have two different species that carry
57:48out the pollination of the passion fruit
57:50plant, you know?
57:51It is not made clear at any point that
57:53one benefits and the other doesn't. So
57:55it can't be that one.
57:56Competition, guys. Competition is the
57:59answer to this question.
58:01Pay attention that it's asking for the
58:02ecological relationship between the
58:04insects, not between the insect and the
58:05flower, but between the insects.
58:08So, since both insects pollinate the
58:10passion fruit plant, what will they have
58:11between them?
58:13They will have a competition between
58:15them, since they are disputing the same
58:17resource, which is the passion fruit
58:19plant, right?
58:21So, the answer is letter C. Guys, these
58:23were some questions that appear every
58:25year on the Natural Sciences exam, and
58:27if you grasp the reasoning and the
58:29concepts I explained here in the video,
58:31you will be able to get them right
58:32without difficulty.
58:34These are simple questions, questions
58:36where you just need to have conceptual
58:38mastery to get them right. And I covered
58:41the bulk of what you really need to know
58:43to get most of the standard questions
58:46that appear on these topics and subjects
58:48here in this video. So, please, if this
58:50helped, leave a like to support the work
58:53, and look, we're going to have the
58:55biggest Black Friday in the history of
58:57Protocolo ENEM this November, with the
59:00best teachers in Brazil, the best study
59:02material, Q&A support, mentoring with me
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59:07and many special novelties that we are
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59:27that's it for this video. I truly hope
59:28it has helped you out. We're in this
59:30together, and see you next time.

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