Transcription
For this question, okay? The diagram shows a human body. Identify the system. So, once again, there are two. Okay? State the function part that you need to fulfill. The first part is very straightforward. Identify. Okay? This is straightforward. You see things like the heart, you see things like the blood vessels. So, this must be the, okay, um, circulatory system.
Now, for identification, right? There is no way but to memorize. Okay? What comes together with certain systems. So, for example, in the digestive system, you have your intestines, you have your stomach, you have your, um, gallbladder. All this, if you don't know, I cannot help you. You must memorize. And you need to memorize their function.
Okay? Now comes the second part. State the function of this system. Now, I just want to stress that whenever, okay, if the function has got to do with transport, okay? So, for example, transport. There are two things that you usually, 99.9%, have to do. You have to, number one, tell me, okay, where does this item get transported from, where to where? This is extremely important. So, for example, I don't want to talk about the human circulation system. I can talk about the xylem vessels or the water-carrying tubes in your plants. So, you have to say that water-carrying tubes carry water and mineral salts from the roots to all parts of the plant. From where to where? The second thing you need to state is what substances are being transported. You have to list them down. Okay? You cannot just say, "Oh, substances." No, it doesn't work that way. You have to tell me and name me explicitly the substances. If there are more than, uh, one substance, let's say multiple, okay, more than two, you have to name at least two. If not all. So, if you are good, then name everything. If not, you must list down minimally the two main ones.
Okay? So, for this question, you know that the circulation system is a, it's got to do with transport, transporting substances around your body. So, because they talk about the circulatory system in general, right? You have to say, "Transport substances around the body" or "throughout the body." However, you cannot just say "substances." You have to say, list down at least two types of these substances. So, the answer will be: Circulatory system, okay? Transports digested food and oxygen throughout the body.
So, can you see that I'm actually, for viewing two items? The first thing is I'm talking about direction. Okay? So, in this case, it's "throughout the body" is the direction. Because the circulatory system circulates, it goes round. So, in this case, this is not really like a final destination from somewhere to somewhere. No, it just circulates. But I must talk about the direction. After that, I must list down explicitly what are the substances. Now, oxygen and digested food are just two of the main substances that it transports. There are many other things. For example, your blood also, uh, also transports things like, um, uh, nutrients. Okay? Nutrients is not very good. It transports things like vitamins. It can transport waste products such as, um, carbon dioxide, urea. It also transports water. So, all this can be listed. Any one of these. But the two main ones would be food and oxygen. And make sure the word "digested food" is here, because obviously you cannot be transporting a hamburger throughout your body.
Blood vessel. Then the next thing is, you also cannot tell me, "Transport blood." Why not blood? Because blood is part of your circulatory system. It's like, it's like you're transporting yourself. Does not make sense. Because it's like you say, "Oh, I'm transporting my arm." But my arm is part of me. So, it does not make sense to say "blood" in this case.
Next, name. Why? Pretty straightforward. Okay? I think most of you got it. Okay? It's the heart.
Okay? Now, other than why, name another two parts of this system. Now, some of you actually put veins and arteries. While they are seemingly two different things, they belong to the same class or family, which is actually blood vessels. Right? So, a higher-order answer would be blood vessels and blood. So, you can say blood or blood cells. Blood is actually a liquid tissue of your circulatory system. What is included in blood? Include white blood cells, red blood cells, plasma, etc., etc., etc. But yes, blood itself is a part of the circulation system. Okay? As well as blood vessels. Blood vessels, I know there are three types. You have your capillaries, arteries, okay, um, and then you have your veins. Okay? Now, if you want to go even deeper, you have your arterioles and then you have your venules, which you do not learn at this level. But essentially, they are all blood vessels. Okay? So, that's why in your question paper, if you put artery and vein, I would have remarked that as same. Actually, not same, like I would say similar. No such thing as same, but they are similar.
Next. This is pretty straightforward. Okay? How are the seeds of E and F dispersed? So, when you look at this question, you have to look at the diagram. Wherever they draw a diagram for you, it's not for fun. One. So, when you look at E, you see structures like this, feather-like structures. They can capture wind. This will give you the hint that, hey, this is actually a wind-dispersing plant. And then you look at this, and sometimes you see all these motion things. This will tell you that it's explosive. I stress again, it's explosive, and not explosion. So, if you put "explosion," don't laugh. It's as if the parent plant explodes every time it reproduces and disperses. It explodes. Very soon, this plant is going to go extinct. Okay? So, this will be by wind, and this is by explosive action, not explosion. Stress again.
All right. State one advantage of the method used by F to disperse its seeds. Now, a lot of you tell me that, "Oh, it's to avoid overcrowding and not, uh, and to reduce competition." No, that is not correct. Naq, not answering the question. They ask you what is the advantage of the method. They never ask you what is the advantage of dispersing the seeds further away from the parents. In fact, when you think of it, right? Okay? When you compare the two, okay? What is the difference? The difference is that one is by wind, and one is by explosive. Is the method of dispersion? If you compare the two, uh, I would say that E will probably travel further than F. Right? So, but then, so what is the advantage? When you compare the two, the difference is this is dependent on wind. Right? It is wind. Okay? Whether or not it gets dispersed well. I must still see whether you know, check the weather forecast. Got wind or not? No wind, that's it. Okay? But for F, it doesn't matter. Explosive mechanism depends on itself. It doesn't need to wait for any pollinators or pollinating agents, okay, or factors such as your wind or your water.
So, how would my answer look like? Okay? So, your answer could be: It does not depend on any external factors for dispersal. So, the external factors could include your pollinators or your pollinating factors such as wind or water.
This one. John conducted an experiment to find out if the wind affects the distance moved by E. Whenever you have an experiment, this is very important, children. Whenever you have an experiment, the first thing you do after reading it is to annotate, which is your change variable, and which is your measured variable. Okay? So, amount of wind, in this case, to find out if amount of wind affects. So, this is your change variable. Distance moved, okay? So, this is your measured variable. This is very important because it helps you clarify what can be changed and what cannot. At the same time, it will tell you what are you measuring. John repeated the experiment five times with all the factors kept the same except for one. Suggest two possible ways of varying this factor.
Now, the first thing you need to annotate is "asset for one." This one refers to the change variable. And if you have annotated as I told you earlier, you would know that the change variable refers to the amount of wind. Okay? Now, when they ask you to suggest a way, you must tell me what do you need to do. It's like an action. You cannot just say, "Vary the amount of wind." You don't realize that you're just copying here, right? "Oh, change the wind. Change the amount of wind." Isn't it just here already? It's different already. You have to tell me what do you need to do explicitly. Okay? So, what can you say? The first method you can say would be to change the wind speed of the fan. Okay? You're doing something, like you press the button, okay, to change the wind speed. The second thing you can do is to change or adjust the distance of E to the fan, right? At the start. So, instead of putting here, maybe you put it further away. So, when you put it further away, the distance increased, right? So, right at the start, the amount of wind that is reaching, um, this new point, that's called this point X, would be more than than another one. So, because of that, you already have varied the amount of wind speed. But you have to tell me it needs to be an action. It cannot just be, "Oh, change the wind." Uh, "change the amount of wind." You're not exactly helping. Okay? So, it has to be "change the wind speed of what?" The fan. It cannot be just, "Go change wind speed." Wind speed, what do you do? You blow harder to change wind speed? Do you, literally, take a fan and fan harder? Okay? Do you change the wind speed of the fan? Okay? So, it has to be something that is a tangible action that can be done.
All right. Question 31. So, question 31 is a transport in plants question. Now, this is quite a typical question whereby they will ask you to identify the various parts of a plant system based on the type of substance that is being transported or the direction of the substance being transported. So, let's take a look. So, the diagram below shows how substances are being transported in a plant. P and Q represent different parts of the plant. Okay? The arrows represent the movements of substances G and H. Right off the top, when you talk about substances of a plant, okay, you what should come to your mind will be things like water, okay, and your food. So, food in this case will be your glucose, okay, will be your glucose, okay, that's being transported around the plant. Now, you should also start to think that the, no, sorry, the source of these two items. Where does it originate from? So, from your food, it will originate from your leaves, because that's where your leaves would have produced the food. And for your water, it will originate from your roots, because your roots are the one that would have taken in water. Okay? So, just by looking at it, you can do a little bit of annotations already, and you can figure some things out.
So, if you take a look at H, H actually originates from the roots. Right? So, from the roots, it goes up. It goes to flowers, it goes to, um, leaves. So, because it originates from the roots, right off the top, you would have known that, okay, H could very well be your water. Okay? Now, it is not just water, okay, that is being transported. It has to be dissolved mineral salts. So, because these mineral salts are dissolved in water, when your roots take in the water, okay, your roots will take in the water together with the mineral salts. So, in your question, if they ask you what type of substances are being transported, you have to mention both, okay, together.
Next, for G, I can roughly guess what is G because it originates from Q. It originates from somewhere, okay? So, it goes to the roots. Okay? It goes in the opposite direction of your water. So, in this case, I can actually guess that my G most probably would be food that was being made by your leaves. And since, okay, I know G is food, and it originates from Q, I can be certain that Q will be my, um, sorry, it will be my leaves. Then, after that, I look at P. P is one part of the plant whereby all substances passes through it. So, whether is it food, or whether is it water. So, therefore, my P, I can be quite certain that this is the stem. Because the stem contains both your xylem and your phloem vessels, your food and your food and water carrying tubes. So, because they are both present, I know that this is my stem. So, therefore, P will be stem, and Q would be leaves.
The next question. Identify substances represented by H and describe how these substances. Okay? So, the fact that they put their "substances" is already a very big hint, okay, as to what, um, it might be. It cannot just be one substance. But most of you just wrote it as, um, water. Okay? And that is the problem. Okay? When you just say it's water, because it's more than just water. It's actually water together with mineral salts. So, H. So, how would the answer look like? So, it would be something like: H are water and mineral salts.
Now, okay, so water and mineral salts. Now, if you look at it, right? "Describe" is the next keyword. So, it cannot just be saying, "Oh, it's transported from here to there." You must tell me by what. Okay? So, you need to be able to say a few things. So, you know that what are the things that are involved? You know there is a direction, because I told you this many times. When it comes to transport, you always have to tell me from where to where. Okay? Because it's a transport function. Secondly, you must name the substance. And the additional point for this is that you tell me is through what? And in this case, that will be your xylem vessel or your water-carrying tubes. Okay? So, your answer should contain these three points. So, you would say: Water and dissolved mineral salts are taken up by the roots and transported to all parts of the plant via the water-carrying tubes.
So, where are the points? Water and dissolved mineral salts. You talk about what is the substance being transported. Taken up by the roots and transported to all parts of the plants. From where to where? And lastly, through your, uh, water-carrying tubes.
Now, some of you actually, instead of telling me "all parts of the plant," y'all told me "to the leaves" or "to the flowers." Now, most of the time, I would prefer you to be more specific. So, what you're doing is not wrong. However, in this question, because water really does get passed on to every single part of the plant, so the more correct term to use would be "all parts of the plant" instead of just being specific. Because some of you just talk about leaves, but it also goes to the flowers. And some of you will tell me, "Oh, go to leaves and flowers." That's good. That's even better. But have you ever considered that this plant might have fruits in the future? Okay? Or actually, there are fruits, it's just that it's not mentioned in this question. Okay? So, water will go to these areas. So, just put "all parts of the plant."
Moving on. Okay. This question. Oil is sprayed on stagnant water as shown. Explain how this prevents mosquitoes from breeding. Now, whenever they show you a diagram, okay, it is very important that you take note of, um, the picture. You cannot just be saying answers based on your prior knowledge or based on what you have read. One look at it, and you know you see words like "breathing," you see words like "mosquito." It should hint you that the topic that they are, um, uh, testing you on would be life cycle, correct? And they are testing you on, uh, the life cycle of mosquitoes.
Now, for this question, take very careful note of the diagram. The diagrams are always there to help you. So, in this case, we know that there is a mosquito larva. Okay? There is a structure over here. Now, this structure, if you notice, it is being blocked by the oil. So, this structure is actually your breathing tube. Okay? This is actually a breathing tube. Now, many of you have told me things like, "Oh, air cannot be dissolved in the water" or "oxygen cannot be dissolved in the water." Okay? It cannot go from the atmospheric air cannot be dissolved into the water. But here's the thing. Most mosquito larvae, they do not breathe through gills. That's the issue here. So, it doesn't matter whether or not, okay, my oxygen gets dissolved in the water. So, even though if my lots of oxygen get dissolved in the water, and my breathing tube is still blocked, my mosquito larva will still die because it doesn't, it doesn't breathe through gills, but it breathes through your breathing tube. And that's where you lose the marks because you, your, the way you phrase it would be something like, "Oh, um, oxygen cannot be dissolved in water." But that's not answering the question. So, make use of the picture. Okay? So, it's because your breathing tube is blocked by the oil, okay, your mosquito is unable to breathe. So, there are, you can also say, unable to obtain oxygen. Okay?
So, how would the answer look like? So, you would say: The mosquito, sorry, mosquito larva. Okay? Be very careful if your food mosquito is wrong because most people is the adult version. Okay? In this case, they're asking about mosquito larva. Breathing tube is being blocked by the oil, hence it cannot breathe.
All right. I hope that's clear enough. All right. Okay. For this question, malaria is a disease spread by mosquitoes. A child infected with malaria is found to be bitten more often by mosquitoes. A. Joel wanted to find out if the children infected with malaria are more attractive to mosquitoes A due to a certain smell that they produce. He used a setup shown with twenty mosquitoes A in box P. Okay? Joel counted the number of times the mosquitoes landed on the shirt for three minutes. He repeated the experiment using another shirt worn by an uninfected child in box Q. So, once again, we need to do some annotation.
Now, for this question, um, it's testing you on your experimental techniques and your understanding. So, in the first question, they say, "State a hypothesis on how the smell on the shirt affects its attractiveness to mosquito Q." So, what happens over here is, first, you must understand what is a hypothesis. So, a hypothesis is basically something, an idea that you have that you want to prove whether it is correct or wrong. So, for example, I can say, and in a very simplified manner, okay, "Drinking more milk will help you increase in your height." That is a hypothesis. Okay? A logical, uh, deduction based on your knowledge because milk has calcium, and calcium and, um, you're born to grow. Okay? Think about it in that sense. So, it is an idea, okay, that you have, and you want to prove whether or not it's correct. So, when you look at this question, right? It's an experimental question. So, the first thing you do is actually to identify the change variable and the measured variable. So, basically, the change variable, all right, would be that one shirt has, um, the smell of an infected, infected child, right? Okay? And another one does not have. So, this is actually, so the smell of the shirt, okay, is actually the change variable. And then the measured variable is basically the time, the number of times the, the most, the mosquitoes actually land on it. So, having said that, think about it. Based on the statement, "Drinking more milk will help you increase your height," use that format to help you form a hypothesis for this question. So, in this question, remember the change variable is actually whether or not, um, there is smell or no smell on the shirt. So, it'll be something like: "The presence of smell on the shirt increases the attractiveness for mosquito A." Okay? So, so you want to see whether this idea is true or not, then you carry out this experiment to prove it. Okay? So, that is what a hypothesis is all about.
Now, some students would tend to actually relate this idea with the child itself. So, you would say something like, "Oh, an infected child, an infected child would attract, um, oh, okay. An infected child would increase the attractiveness for mosquito A." That is not correct. Why? Because in this case, we didn't put the child there in the experiment. We used the, the smell. Because when you say "an infected child," right? There are so many reasons why the child is, um, became more attractive. It could be the smell. It could be the, some substance in the blood. It could be a kind of secretion that is being emitted by the child's body. Okay? It could be the temperature of the child. Okay? Because temperature is known to, to higher temperatures are known to increase the rate of mosquito bites. So, because of all these factors, you cannot say that "an infected child would increase the attractiveness for mosquito A." That's not right. Because your experiment looks at the smell. That is your change variable, and it has to go hand in hand with your hypothesis. The presence of smell. But, okay, you can also flip it around and say, okay, "The absence of smell decreases the attractiveness for mosquito A." That is fine also. It's another hypothesis. Same thing, but phrased in a different manner, in a negative manner. But that's fine.
Moving on. Okay. Now, this is actually, once again, I stressed many times. You need to be able to differentiate between fair test, accuracy test, and reliability. So, first thing I see in this question, they're asking for accurate results. This has got to do with accuracy. And when it's got to do with accuracy, I'm interested in the measured variable. So, in the experiment, we didn't know that the measured variable is actually counting the number of times the mosquitoes landed on the shirt. So, you need to count. So, when you think about it, how can you make this counting more accurate? More perhaps even easier? Okay? So, you think about it. If I use, that is the opposite of white. Think about it, right? The opposite of white is actually black. So, when you have a black shirt, uh, you cannot say that mosquitoes, because mosquitoes are black in color. Then you realize that, ah, if I change it to a white shirt, there is contrast between the mosquito and the white shirt. Therefore, when I count, I'm able to see the mosquito clearly and I can count them easily, making my results more accurate. And the counting of it has got to do with your measured variable. Okay? Nothing to do with repeating the experiment. Nothing to do with having the same starting variables except for one. That is fair test. This is on accuracy. Okay? So, your answer would be something like: Okay, um, okay, by using a black shirt, sorry, a white shirt, the mosquitoes can be seen clearly and counted easily. Okay? In this case, I guess you can actually just use the word "accurately" as well. Okay? Because you can see that. All right.
The next question. This is actually a generating possibility question. So, it can come up for any topic. One. So, if you take a look at this topic, now, it's, it's like there's no one fixed answer that you learned before. Okay? It's not really a topic of, um, life cycle. It's not really a topic of anything. Okay? It's really testing you on experimental knowledge and experimental design. So, basically, right, if you take a look at it, okay, it's generating possibilities. Okay? This question. Scientists are able to store the smell produced by infected people in a container. Suggest how Joel can use this smell and his results to reduce the number of bites on people.
So, basically, if you take a look at it, you'll know that shirt in box P, okay, let's do some annotation. So, shirt in box P is the one with the smell. Write it down. So, the one with the smell, right, actually, okay, is able to attract more mosquitoes. All right. So, we know that mosquitoes, they are basically attracted to your shirt in box P with the smell. So, ask yourself, okay, what can I do with this? And one very obvious answer is, I can actually attract mosquitoes with this shirt with the smell. So, if I put this shirt with smell further away from a crowd, it will actually lure the mosquitoes away from groups of people. Okay? That's one possible answer. Another possible answer that I think is plausible is to actually make use of this smell to trap the mosquitoes. So, by doing that, right, you physically remove the number of mosquitoes that is in the environment, hence reducing the number of people, okay, being bitten.
All right. Moving on. Okay. Next question. These are commonly found near flowering plants. So, straight away, I see bees, I see flowering plants. The first thing, that topic that comes to my head would be reproduction in plants. So, right off the top, things that will start ringing in my head will be pollination, fertilization, stigma, anther. All these things should actually, okay, come in my head straight away. So, the first question asks, "Describe how, okay, these help plants to reproduce."
Now, let's take a look at a few things. Despite and bees. So, "describe" means that I'm not asking you to state a function. I'm actually asking you to tell me, okay, how is this process being carried out? "Describe" is like, tell me how. It's not just about stating a process. The next thing, bees. How? What is the? Ask yourself, what is the function of bees in the world of plant reproduction? And you will understand that it's actually got to do with pollination, because it is a pollinator. All right. So, obviously, the process that it carries out is pollination.
Now, remember I told you whenever it is a transport function, you need to actually tell me, transport what? From where to where? And by what? So, you need to tell me: Bees help to pollinate flowers by transferring pollen grains from the anther to the stigma. This is extremely important. So, what am I looking for? Once again, I told you, transport function, right? So, firstly, from where to where? From the anther to the stigma. Transport what? Pollen grains. All right. So, this, um, strategy of answering when it comes to transport will follow you through all the way to secondary school, even beyond. You must tell me, transport what? From where to where? Have any missing point, deduction of marks. And you cannot just tell me, "pollination is like just taking that function." Okay? So, it's only half a mark.
Next. Season investigated the effect of substance N on bees with two containers R and S of the same cage using a circular cage. Okay? So, what's the change variable in this case? Presence and absence. Change variable. Okay? Justin then introduced bees into the cage and closed the opening. She counted the number of times bees visited each container for a duration of three hours on day 1, 5, 10. So, basically, the change variable in this case is actually the number of times the bees, the bee visits. Sorry, this is the measured variable. Okay? The change variable is whether or not, okay, and it's present. So, in this case, in container R, it's only sugar water. In container S, it's sugar water with substance N. Okay? So, you want to see whether or not substance N is going to affect, okay, um, the times, uh, the number of times the bee visits it. Okay?
So, the first question asks, "Suggest how the arrangement of containers R and S allow for a fair test." So, straight away, you once again, I tell you already, you must know what's how to differentiate between fair test, reliability, and accuracy. This three. So, in this case, fair test is actually concerned with your change variable, or rather, one change variable. So, because it is concerned with your one change variable, you actually have to make sure that, okay, everything else is the same. Right? But in this case, they specifically talked about, um, the containers. So, ask yourself, by putting them in such an orientation, what will your containers, uh, how will your containers make it fair? Which aspect is it making it fair? Now, some students actually say things like, "Oh, container R and container S, they are of equal distance from each other." My question to you would be, how can they not be equal distance when there's only two of it, R and S? So, whether you go by this direction from this point to this point, or this point to this point, the distance is the same. So, this child actually understood that the distance from the entrance is the same for the bees. So, they have to travel the same amount of distance to reach the containers. All right. So, by putting in that in such a manner that will ensure that that happens. However, it is the phrasing of it that is inaccurate. So, be careful how you phrase it. So, in short: These need to travel equal distance to both containers from the entrance. Right? Then it makes sense.
Okay. The next, um, question is extremely important. Now, um, for the past few years, right? There are a few questions that you see that in PSLE always comes out. For example, you know that water cycle questions always comes out. It's just that it comes out in a different form. Right? It's always application-based. For example, you have the one that is whereby the ice is taken out, and then after that, it forms the mist. Correct? And then after that, you have another one that talks about, um, the, uh, condensation, okay, of the, uh, on the glasses. All right. Alice and Beatrice. And then you also have another water cycle question that is on, um, the, uh, sausage. For this year's paper, really, really. So, that is one commonly tested item that I, I realized. Another one, okay, is on graphs. Nowadays, they like to test you on graphs. Okay? One exam, what another example would be the graph on the mosquitoes' breathing. Remember the question whereby the death rate of the mosquito remained constant, but the birth rate declined? Okay? So, this is another question on graph trends. So, you must be able to identify graph trends and read them. Now, usually, I'm not saying, I'm not saying that it is definitely a master the graph that they give you. If there are two items, usually there are two trends. There can be more, they can be less. But look carefully.
So, in this question, is this that the number of times bees visited both containers on day 1, 5, and 10 are shown in the below. Okay? So, container S is the one with substance N and no tape. So, that you can make, so that you can understand the graph clearer. So, that you have to keep referring up and down. Just a simple annotation will do. And this is just sugar water. This also has sugar water. Okay? The difference is that it has N added to it. Now, then after that, they ask you, "Describe how substance N affected the numbers of bees visiting both containers from day 1 to 10." Okay? So, keyword here is "describe substance N affected number of bees." So, what you do is, you take a look at all those with substance N, which is actually container S, okay? And then you compare it with the one that does not have substance N. So, you realize that on day 1, they are essentially more or less the same, right? Day 5 and day 10, only then do you see that there is an increase, all right, in visitation to container S as compared to your R. Similarly, with day 10. So, in short, there are two trends here. The two trends that you need to recognize would be that the first trend is on day 1. The number of times the bees visited container R and S, there's no difference. But the second trend only starts to happen on day 5 and 10, whereby you see that substance N actually caused an increase in visitation by the bees as compared to the container with no substance N. So, do you see the difference now? It is actually two trends. So, you cannot make a sweeping statement, which most students did. They just went, "Oh, substance N increased, um, the visitation of bees in container S." That is not true because it did not happen for day 1. So, by saying that, you're making a sweeping statement by saying that, "Oh, all, all three, uh, for all three days, 1, 5, and 10, there was an increase for, uh, sub containers with N," which is not true. So, therefore, you have to, you have to be very careful about what you write.
So, how would your answer look like? So, obviously, two trends. You talk about two trends. So, at day 1, describe, right? So, "At day 1, substance N had no effect on the number of bees visiting the containers." R and S. "More bees visited the containers of the container, sorry." Can I change this? "More bees visited container S with substance N on day 5 and 10." Okay? So, the two trends, if you look at it, the first trend is here. Day 1, substance N has no effect on the number of bees visiting containers on S. That's why they are the same. Trend two: "More bees visited container S." So, can you see this is container S here? This is container S here, okay, with substance N on day 5 and day 10. So, there are two trends. Very important. One trend, two trends. So, look carefully in your exam. Don't make a sweeping statement.
All right. Moving on. Next question. Jaden placed the same amount of pond water which contained tiny pigments into two identical glass containers A and B. He painted container B black. Okay? So, straight off the top, when I see these top questions, okay, I will have some inkling that, okay, you have two containers. You can take, you pay one black. Usually, when that happens, and with living things in it, right? I'm thinking at the back of my mind that black usually relates to, like, cannot enter. It could just be about, yes, but I should get some inkling. Okay? Okay, no light. That means, okay, which are the topic that I'm thinking of that has no light? Living things. You know what? I think it's going to go in photosynthesis. No light, so no photosynthesis. Okay? So, that will give me, uh, a hint that it could, it could be a topic that's testing on photosynthesis. Then I go on to read. He placed both containers at the same place under bright light. Aha! Okay. Under bright light. Okay? So, this is another big hint that tells me that it is photosynthesis. Then I must start to think, oxygen, photosynthesis. Are they related? Yes. Because in photosynthesis, you will produce oxygen. So, yes, okay, they are sort of related.
So, now that we are done zeroing in on what is the topic of concept that's being tested here, let's take a look at the experiment. So, first things first, like I always tell you, you must tell me what is the change variable. So, the change variable is actually, in this case, talking about your container that is being painted black, another one that is clear. So, that means this is my change variable. And what is my measured variable? Very clearly stated here. My measured variable is actually the amount of oxygen. Okay? With that, let's jump into the question. So, the question asks you, "Explain why the amount of oxygen in container A increased while the amount of oxygen in container B decreased."
Okay? So, let's highlight some points. Oxygen A increased, contrast to oxygen B decreased. First things first, we know that in photosynthesis, oxygen is reproduced. So, in A, if it, because it's a clear lid, you'll be able to relate that, okay, photosynthesis is able to happen. Check. When photosynthesis happens, it actually produces oxygen. And that is only because you're able to have light entering. As opposed, you should always compare and contrast because now the question is actually asking you to compare. Take a look at this. The word "while" is here. So, this tells me that I need to compare. Okay? So, when I look at this other experiment, like I said earlier, no light can enter, no photosynthesis. But that doesn't answer the part about why my oxygen level is decreasing. No photosynthesis, it should just be constant. How come it's still decreasing? That is the question you need to ask yourself. And that's because respiration is always happening, okay, for living organisms. So, there's one additional point here, is whereby respiration will still continue to happen, and through respiration, you have to take in oxygen, causing your oxygen to be depleted. It's not to say that this side don't need respiration. Ah, this might also need respiration. I want to be very clear about this. The difference is that the rate of photosynthesis, or rather, the rate of production of oxygen through photosynthesis is higher than the rate of oxygen being taken up for respiration in this case. So, there's excess oxygen being given out. There's something that is, uh, very crucial.
So, after we annotate already, right? We already know what we need to talk about. In A, we've talked about light being able to reach A, photosynthesis must occur, resulting in production of oxygen. And B, as the same, no light, so therefore cannot photosynthesize. Respiration occurs, leading to the, uh, to the depletion of oxygen. Okay? So, can you see how annotation actually helps you to answer the questions, or at least know what are the demands, okay, of the questions? Okay? So, you say: "Organisms in container A is able to obtain light for photosynthesis to produce oxygen, while plants, use contrasting word, plants, okay, of our organisms in container B is unable to obtain light for photosynthesis. The organisms in B take in ox, take in oxygen for respiration." So, this part will explain why there is a deplete in oxygen. This is the part that many students may stop. They just think that by just simply mentioning about, "Oh, organism B cannot photosynthesize," it's sufficient to answer. No. If you just put this, what it tells me is that then, stress again, my oxygen levels should remain constant. How come it's depleted? It's because it's due to respiration.
Next question. Suggest one possible result that could have resulted in Jaden obtaining inaccurate results. Is this a fair test, accuracy test, or reliability question? Can you see how many times this type of question appeared? So, if y'all don't learn how to differentiate, you're going to be in trouble. So, very straightforward. This is accuracy. And accuracy has got to do with measured variable, which I've stressed umpteen times now. The measured variable in this case, if you look at it, is actually the amount of oxygen. It's clearly identified earlier on. So, you ask yourself, okay, what did Jaden do during the obtaining of the measured variable that could have resulted in inaccurate results? It has got nothing to do with the number of organisms, okay, or the type of organisms at the start. A lot of students put that. But you think about it. If you put that answer, is that answer more suitable for a fair test question? It's a fair test answer, right? Because all, in, in fair test, we are concerned with having only one variable. In this case, the one variable is actually your, um, whether there's light or no light. Everything else should be the same. So, by having more than one type of organism or having more, a different number of organisms, you are actually introducing an additional variable, which becomes an unfair test. In this case, the question is not asking you about that. It's asking you about inaccurate results. And that has got to do with your measured variable. So, the correct answer should be: "When the lid is opened, some of the oxygen will escape, leading to inaccurate results."
So, why? Because remember, he told you he measured on a daily basis. And every day, if you look at the setup, he has to open the lid in order to measure. One every time he opens it, the oxygen will run off. So, how can he say that, okay, you know, definitely this is the amount of oxygen that is being produced? Think about it. So, his results become inaccurate. And that is the most correct answer. Now, if extension questionnaire, if they ask you, "How can he get more accurate results?" The answer for this would be to use an oxygen probe. Okay? Use a data logger with an oxygen probe. So, later, I will show you what is it. It's basically just a device. A probe is just a device that is able to capture information using a computerized, using technology to capture information. So, it's very accurate. Later, I will show you what is a probe. In fact, there is the next question we are talking about temperature probe. Okay? So, instead of a temperature probe, you change that, you change to oxygen probe, then he would not have to open the lid.
Okay. Silver sticks, uh, sorry. Silver boiled some water in a pot on the stove. State what boiling means. Now, first things first, be very careful. Uh, they say "boiling up," not "what boiling of water means." So, in this case, you cannot tell me 100 degrees because different substances boil at different temperatures. So, because of that, you need to use the word "fixed temperature," and you have to mention the state change from what to what. Okay? So, you have to say: "Change of state from liquid to gaseous at fixed temperature." So, those of you who write 100 degrees, right? I would, I would strongly suggest that you change it to, um, "fixed temperature." And also, don't tell me "steam" because they, months again, is very specific to water. They ask you what is boiling. They never say what is boiling of water. Okay? Be very careful about that. So, this is a definition question. All right. You have to get everything correct. Okay? Um, once again, we realized that definition questions are getting more and more common. So, it is very important for you to memorize. Usually, definition questions are a type of process. Evaporation, condensation, okay, fertilization. All these.
Next question. Silver wanted to cook some egg at 80 degrees. Silver wanted to cook some egg at 80 degrees. When the water boiled, she removed the pot from the stove and added some cold water. She then put in some eggs and covered the pot for 10 minutes. Okay. All right. So, without preheating the pot, highlight, underline, "without heat in the pot." Suggest two ways that Silver can make sure the water was kept at 80 degrees in the same pot.
So, few things. You realize that you're not able to change certain things. So, these are the few things that you need to actually make sure that you don't change. Reheating the pot must be kept, kept at 80, and must be the same pot. So, some of you would have said things like, "Oh, change the pot to a plastic pot." But you cannot do that. And you also cannot reheat the pot. So, some of you also gave questions like, "Oh, put a heating pad on the metal pot," or you say things like, "Oh, make the metal, install a heating device on the metal tabletop." But the question already states, "cannot reheat." So, it doesn't matter. I know some of you are thinking, "We heat means put fire." No, any heating element cannot be used here. Okay? So, because heating element cannot be used here, okay, and you want to keep the heat in, think about it. The one way that you can do is to actually put a layer of insulation around the pot to reduce heat loss. Right? And some of you tell me, "Change the metal tabletop to plastic." But the point is, yes, plastic is a poor conductor of heat, correct? But you don't forget what happens to the rest of the pot. It is still being exposed to the surrounding, which is of a cooler temperature. So, because of that, heat can be still lost from these surfaces, even though your metal tabletop has become a plastic tabletop. So, the first solution is really to wrap it, okay, or put it into an, uh, into a poor, a material, a rapid material of poor conductor of heat. Now, be very careful. A common misconception that I find is students will tell me, "insulator or heat." No such things. Okay? Please be very careful. Insulators are only used for electrical components, okay, not for heat. That is a common misconception.
Now, then the next thing, how to solve your temperature issue? Now, this is what I'm talking about. It's a temperature probe or temperature sensor. So, in the previous question, you could change this to, um, use an oxygen sensor or oxygen probe. That would have solved his problem and make his measurement accurate. Now, back to this question, how to maintain at 80 degrees without reheating? So, obviously, this question.
Is testing you okay? So, the first one is testing you on conductors of heat. The first method that they want you to talk about because you want to reduce heat loss, man, correct?
The second method is actually testing you the concept whereby heat travels from a region of higher temperature to lower temperature. So, you think about it. I cannot reheat, but I can pour hotter water, water of higher temperature, right? Now, I can pour boiling water into this, okay, and raise the temperature up. So, if this drops to, I don't know, maybe 70, 70 degrees Celsius, I will add boiling water, which is 100 degrees Celsius, and then because it is hotter, okay, the heat will travel from the hotter boiling water to the cooler 70 degrees water, bringing up the temperature. And I can add bit by bit until it reaches 80. Every time it drops, I'll add a bit more boiling water, okay? And that is how you maintain it.
So, how will your answer look like? Okay, so number one, place a covering, a poor conductor of heat, around the pot. Two, add boiling water to the pot when its temperature decreases below 80 degrees. Now, take note, uh, some students would have said that, uh, add water that is of 80 degrees. If you add water that is 80 degrees, you will never rise, raise the temperature until it's at 80. Why? You imagine if this was at 70 degrees, you add water that is 80 degrees, okay? Heat will travel from 80 to 70, but the very, very most that you will get is 79.9 degrees Celsius, maybe, I don't know, but it will never reach 80 degrees because heat is always being lost from your 80 degrees water. So, be very careful about that. Adding 80 degrees water won't cut it, won't help, okay? You add until the water overflows, you will also not reach 80 degrees, okay? All right.
Question 36. Ravi wrote a metal ball from point X at a low speed past a strong magnet on the table, as shown. So, from here, once again, we should always try and annotate. So, the first thing we notice is that words like metal ball and strong magnet, this signals to us that probably this topic is probably on magnets. And don't forget, next is actually related to forces. Magnetic force is actually a form of non-contact force, okay? That is something we need to know.
Now, let's move on. Explain why the metal ball moved past the magnet in a straight line. So, over here, you realize that, okay, technically, okay, if it's if it's a straight line, what it means is that the ball is going in a straight line. It is not affected by the strong magnet at all. If it's getting repelled by the magnet, it should move in this direction. If it's being attracted, it should move in this direction instead. It moved in the straight line. So, this means that, okay, there is no effect. The magnet has no effect on the metal ball. So, this tells me that the metal ball is actually a non-magnetic material, right? So, the metal ball is made of a non-magnetic material.
Now, some students tend to have this misconception that if it's metal, it's definitely attracted to a magnet. This is not true. So, to help us identify what are the methods, okay, that is magnetic, all right, we have our coins. C-O-I-N-S. C-O stands for cobalt, I stands for iron, N stands for nickel, and S stands for steel, okay? Now, be very careful. C does not stand for copper. A lot of students think that C stands for copper. That's why it's C-O, cobalt, okay? This is very essential to remember to help you.
Next, he next wrote an iron ball, okay, from X in the same way. So, based on what I explained to you earlier about coins, you know that iron is actually a magnetic material, and that is the main difference, okay, between the first question and the second question. So, when you look at questions like this, one way to end a form of annotation is to compare the first scenario versus the second scenario. In fact, this is a little bit like an experimental question. The material of the ball is, in fact, a change variable.
Now, then they ask you, which path of the iron ball, Q, R, K, Q, R, S, or T, did the ball take? Now, your answer for this, all right, uh, many students actually wrote Q. Now, they, um, they selected Q because they understood that iron is actually a magnetic material. So, because it is a magnetic material, it would be attracted, okay, to the magnet, correct? So, this was something that is correct. However, they selected Q, but take a look at Q. When you follow through with the trajectory, it actually goes one round, okay? So, if you follow it through, it actually goes away from the magnet. That's not right. In fact, it needs to go near enough to the magnet and then follow this curvature. So, R is a much more plausible choice than Q. And obviously, S is not possible because if you select S, it means that it has no effect at all. And T means that it actually repels. So, for that to happen, your iron ball, it has to be a magnetic iron ball, which didn't happen, okay? So, in this case, your answer will be path R. All right, most plausible one. Iron is a magnetic material, hence the iron ball will be attracted to the magnet, all right? Okay, so be very careful about how you actually select your choices. Don't just Q and R may look plausible. Follow through the pathway, trace it up, you realize that Q is not possible, okay?
Next, this question, okay, this is quite a tricky question, okay, as, uh, you just tend to have issues with, uh, forces. Let's take a look at it. I should type a mess to an electric toy where the mass, the mass is actually over here, as shown in diagram one. The train moves slowly from A to B. Next, I shall link a wagon, okay, to the train, as shown in diagram two. When she places the same mass on the wagon, the train moves faster from A to B. So, this is a little bit, okay, this is, in fact, an experimental question. The change variable over here is actually the presence, okay, of your wagon, all right? And the measured variable is actually about the speed, all right? So, in this case, you need to talk about the change variable, how it affects it, correct?
So, the question asks, give a reason why the train moved faster when pulling the mass on the wagon. So, obviously, you have to justify how this difference of having a wagon will allow the mass to move faster. So, if you take a look at it, the main idea is that the wagon has wheels on them. So, these wheels, right, when you take a look at it, okay, the surface area in contact is actually lesser. That's already one thing. Another thing is that it rotates. So, because of that, right, it will reduce the friction between the wheels of the wagon and the track. Because now the mass is actually on the wagon, okay, but the wagon has wheels to reduce the friction. So, remember, friction is an opposing force. So, your train is trying to move this way, your friction is moving this way. So, obviously, if you reduce your friction, you're able to move at a faster speed, okay?
So, how would your answer look like? The wagon has wheels which reduces friction between. Now, this is very important. Now, because friction is a contact force, you need to have two surfaces. You cannot say "on." You must say "between where and where," okay? So, between the wheels and the track, okay? So, because of that, you're able to move faster.
Next question. The train moved from A to B easily, but moved up the slope slowly. Explain why the train moved up the track slowly. Now, in this question, they did not ask you to actually, um, they did not actually ask you to, um, compare, okay, between A to B and up the slope. They just asked you why, all right? So, there are two plausible reasons. One, you can say that some of the kinetic energy has been converted to gravity, gravitational potential energy, because it's going up. Another one, which is more obvious, would be that when going up the slope, the train is moving against gravity. Now, it is very important that you do not say "overcome gravity," which many students have made this error. Even though I have repeated it, um, ten times, they still think that it's "overcome gravity." If you overcame gravity, your train would be floating in the air. That is not the case, okay? It's just going slower. So, therefore, the answer would be: When going up the slope, the train is moving against gravity, right? So, because gravitational pull is this way downwards, okay, but when you're going up the slope, you're going upwards, right, this way, so you're going against gravity, or against gravitational force, or in the opposite direction of gravitational force, that's fine, okay? Opposing gravitational force, that's fine also. But never "overcome," not in this case, at least.
Next. Now, when you look at questions, right, I cannot stress this. It's very important to annotate, okay? Some of the common strategies I taught you before is to annotate for change variable, measured variable, identify the topic using the the key, um, keywords inside the stem of the question. Now, as an examiner, as a sector, I, I tell you, I will not put in information that is not important because that is just, um, be having unnecessary distractor to the to the student, not fair. So, any information that I put down, it must be important. If not, I wouldn't do it. So, when you look at this question, read: "The train and the wagon were linked by plastic rings." Why are they telling me it's plastic rings? Okay, there must be, it must be a hint, or it must be because I need to address this point, that's why they put in plastic rings.
Now, then after that, they go on to show you this part whereby they tell you that the opening of the plastic ring is narrower, okay? Why did they tell you that? So, they're trying to tell you that actually, unless this ring here can stretch to become bigger, the gap there, there is no way that this part here can go through. This part here needs to be able to stretch so that the gap can be enlarged, okay? And then they go on to stress about the plastic ring again, that is linked to the plastic ring of the wagon, okay?
Now, then they continued the story. "When the wagon was up the slope or on the slope, it broke loose from the train and rolled downwards as shown in the diagram." The plastic rings were linking the wagon were not broken. So, these are all very important keywords. "Not broken." "Go downwards." That means there must be some force pulling it downwards, right? Okay? So, what is the force? It is gravity. So, write all these things down. And then, "how come not broken?" Think about it. It's not broken. They mentioned plastic. They keep mentioned plastic. That means it's got to do with your material. Why? Okay? So, maybe it's got to do with the material. We can write annotations like that. Then you ask yourself, okay, plastic ring, okay, perhaps it's got something to do with it. Let's look at the question. "Explain keyword highlight why the wagon broke loose from the train on the slope without breaking the plastic ring." So, once again, they stress on the plastic ring. So, there must be something to do with the plastic ring, right? And not breaking. So, you ask yourself, okay, how does it link to about material property of plastic? Plastic is flexible. Because it's flexible, you can then stretch this ring here. It can be, it can be, it can be stretched, okay, wider without it breaking. So, that answers the first part. Never break.
Then the next part is, how come it broke loose? Is the next part you need to explain. Now, the train is over here. It rolled downwards. So, because it rolled downwards, there is a force that is acting downwards, and this is gravity. So, because the gravity is pulling the wagon downwards, okay, therefore the two rings are being pulled apart. If you take a look at it, your train is moving in this direction, upwards, and your wagon, okay, is being, uh, gravity is pulling it down. So, these are two opposing forces. So, because of that, your gravity pull, which is acting on your wagon, will cause it to break loose from the train.
Now, I want to stress that just by saying that it has mass over here, or because the the wagon has mass, will not get you marks. Why? Because mass is just mass. Mass is defined as the amount of matter that makes up a particular object or substance. That's about it. So, what was causing it to pull apart, right, is actually the two forces, gravity, and then your train that is moving upwards. They're in opposing directions, okay? So, because of the gravity being, uh, pulling the wagon down, okay, it will cause it to pull apart.
So, how would the answers look like? First thing, tell me plastic is flexible, okay? That's the first thing. The second part is, the opening of the plastic ring is forced open due to the gravity on the wagon. Why? Because the wagon has mass, right? The wagon has mass. The wagon's mass itself has mass, and then there is the mass that's on top of the wagon. So, the wagon itself already has some mass together with the amount of mass that the wagon is handling.
I pause here for a little while, okay? So, some of you are thinking that plastic is not flexible. There are something known as hard plastic, and there, and there are certain types of plastic that is soft plastic. Take a look at, okay, a piece of plastic sheet. A piece of plastic sheet is flexible. It can bend, but is it plastic? Yes, okay? Look at your pencil cases. Some of them, your pencil cases are made out of plastic, clear plastic, which is flexible. Some of your rulers, they are hard plastic. So, how do you know that it's soft plastic or hard plastic? You take a look at here. That's why I told you to look at this part here. They tell you it's narrower, okay? So, the only way that this could have become bigger, the gap here, without breaking, is that if the plastic can stretch, right? So, you have to make logical and sensible deductions when you, when you actually look at questions. Yes, correct. In the real world, there are hard plastic and there are soft plastics. So, you have to make a sensible and a logical deduction that this is a soft plastic using the hints that are given, all right?
Moving on, okay, this question. So, very straightforward. Delete this. This is an experimental question. So, the first thing you want to look for is make sure you have your change and your measured variable while you're reading your question. Said an experiment in the room as shown. There is no wind. He released the odor strip with plasticine at a gently. The places they make one complete swing and then move from A back to B and then back to A. He wants to investigate how the mass of plasticine affects the time taken for 10 complete swings. His results are as shown. So, this is very straightforward. In fact, they even put it in a table for you. So, mass of plasticine would be your change variable, and then after that, your measured variable will be time taken for 10 complete swings.
Now, then after that, they ask you, state two variables that that he needed to be kept constant for the experiment to work. Now, this question, right, your need to understand that you cannot just put things that are very obvious. You cannot just say, "Oh, use the same type of wood." What aspects of the wooden strip? Don't just say "use the same type of wooden strip." There is the height, there is the mass. So, use certain things that are very, very, um, specific, basically. You can actually say that, okay, you care something that is like, um, okay, um, the mass of the wooden strip, okay, that's being used, or you can say the length of the string. You can even say the thickness of the string, right? That's fine, okay?
Next, based on the result above, state how the mass of plasticine affects the time taken for 10 complete swings. Now, if you look at it, this is actually a relationship question. So, that's why reading and trying to figure out what what the question is asking is very important. So, when you look at it, right, you realize that actually, there is no effect. Why? Because can you see this is actually increasing? 10, 15, 20, 25. But over here, it went from 15, drops to 14, then increased back to 15, and then back to 14. Okay, it's like a bit like a roller coaster. And some of the students will happily describe it literally. They go over 10 seconds, it was at 15. Then at 15 grams, it dropped to 14. And then after from 14, when you increase the mass, you drop, it goes back up to 50, 15. No, it's asking for a relationship. So, in this case, there's no effect. So, what would be the answer? B. So, you would say that the mass of plasticine does not affect the time for 10 complete swings. That's it, okay?
C. Suggest one improvement to the experiment to obtain more accurate results. So, like I've told you so many times, uh, accuracy, fair test, and reliability. These three will definitely come up for this year's paper. I'm pretty sure. Last year's paper, it came out so many times already. So, once again, ask yourself this question: What are they testing for? So, they are actually asking for accuracy, right? So, if it's accuracy, it's got to do with the measured variable, not your constant variable. So, a lot of time, okay, students have given answers like, "Oh, repeat the experiment at least three times, then take the average." Or they would say, "Keep the angle, make sure the angle whereby you start, uh, release the swing is the same." But ask yourself this question: The first one, "Keep the angle whereby you release the swing as the same" or "release the swing from the same height." Is that an accuracy answer or is there a fair test answer? It's a fair test answer, right? You're keeping all variables the same except the mass of plasticine. So, that's not actually the answer. And then the next answer that most common answers students will give will be, "Repeat the experiment at least three times and take the average." There's actually an answer that is related to what? Reliability, correct? It's not what is not accuracy also. So, the correct answer would actually be, okay, use a digital stopwatch, correct? Use a digital stopwatch which is able to measure up to two decimal places to get more accurate results. So, if you use an analog stopwatch, okay, you can only have one decimal place, like for example, 15.1. So, if you take a look at this, you can, you see it's one decimal place only. So, you share one that can give you up to a decimal place of two, so 14.99, okay? And that's how you get a more accurate answer. It's got nothing to do with the time. The number of times you repeat, number of times you repeat won't give you more accurate answer. It just gives you more reliable answers, okay? All right, so we have to be very clear between fair test, reliability, and accuracy. What kind of question that will guide you to what kind of answer? Be very careful, okay?
Moving on to the next question, okay, this question. Peter built a door lock as shown. Now, when he closed the switch, the iron bolt move. The iron box is here from the right, okay, away from the catch and to into the, okay, sorry, move to the right away from the catch and the door is unlocked. So, this way, okay?
Now, state why copper, a type of metal, is used to make wires. So, ask yourself, what is the function of wires? So, your wires basically allow electric current to flow through, right? Because of that, your copper must be able to do that. So, ask yourself, what is a property of copper that enables you to do that? Copper is a good conductor of electricity, okay? So, many students have this misconception that, "What is a good conductor of heat?" I'm not interested about heat, okay? So, that's why the annotation here will tell you that it's talking about electricity. It's got nothing but heat. That's one. Two, some of you says that copper insulates. That's wrong also, okay? Misconception.
Next, explain how the door was unlocked when Peter closed the switch. This is a very typical electric circuit, uh, question. So, whenever you see this kind of question, C-E-O is the circuit. So, C stands for, is the circuit closed or open? Can the electric current flow through? And then what is the outcome? So, when this is closed, you will see that electric current will flow through over here. Change this cylinder into an electromagnet, okay? And then the electromagnet will actually attract the iron ball this way, okay? And then when it attracts it this way, it will unlock. All right.
So, how should your answer be? So, remember, the first part, you need to talk about, okay, electric circuit. So, "When the switch is closed, okay, the electric circuit is closed, and electric currents can flow through the circuit." Please tell me that it's "through the circuit." Many students will just ignore this fact and just happily leave out the words "through the circuit." It'll not flow through where, all right? So, then the metal cylinder would become an electromagnet and attract the iron ball, okay?
Next, when Peter opened the switch again, he found that the box did not go deep enough, okay? Didn't go deep enough, okay, into the catch to lock the door properly without changing the iron box. So, you cannot change the iron box, but I can change everything else, and you shouldn't add anything else, okay? Suggest changes to his setup so that he can lock and unlock the door properly. So, what happens here is they are asking for both lock and unlock. A lot of students only talk about unlocking. They didn't talk about locking it. So, if you look at it, the mechanism works this way. To unlock, your iron box needs to go this way. So, how do you make your iron box go further? You make the electromagnet stronger. So, what happens is that it will attract, there's a stronger attraction for your iron box to go in this direction, okay? So, there are two ways. One is that you can increase the number of coil, uh, coil wires. The second is you can actually increase the number of batteries.
Now, then the next thing, how to lock it properly? So, to lock it, right, you know that your iron box needs to move from here into here. It needs to go deeper. So, the key thing is you need to understand that it's the spring that is pushing the ball. Now, having a more compressed spring, or having a stiffer or less spring, won't help because it is attached to your iron ball. The only thing that can help is to have a longer spring. So, with a longer spring, it will actually push your iron ball further in. And then with a stronger magnet, even though your spring is longer, it will cause it to compress more, okay? Because now there's a stronger attachment, all right? So, these two must come hand in hand.
So, your answers can be broken down to two parts. So, to unlock, okay, what you will do is have more coils, take more wire coils around the metal cylinder, hence the electromagnet would become stronger, attracting the iron bar, the iron box, sorry, further towards the magnet. And then to lock it, you would say use a longer spring so that the bob would be pushed deeper into the catch, okay? So, remember, it's a superlative thing. Why? Because it's already an electromagnet. You must use the word "stronger," "further," "longer," "deeper." Okay? This is actually a question, okay, because it's already being pushed in. Now, you have to push it further, deeper, okay? So, this is this kind of things, right? Your superlatives need to be there. It is a must, all right?
Now, the next question, okay, it's actually a water cycle question. All right, the next question is a water cycle question. John placed a pack of brown sausages wrapped in clear plastic from the freezer onto a table. After a long short time, a layer of white solid was formed on the surface of the plastic wrapping. So, some of the key ideas in the stem, "freezer." From the freezer, so this tells me your freezer is actually below zero degrees Celsius. It has to be negative something. It can be negative eight degrees Celsius, negative ten degrees, negative four, but whatever the case, it is less than zero degrees, okay? Therefore, your sausage that is thickened out when it first comes out from the fridge, it is less than zero degrees. So, we can assume that it's negative something. Let's say negative 10 degrees, okay? Your surrounding temperature is about 30 degrees Celsius. So, the air, which contains your water vapor, is actually warmer than your sausage over here. So, what happens is that the water vapor, okay, will touch the surface of the sausage and it will actually condense, lose heat, and condense to become liquid water droplets, okay? So, when it becomes liquid water droplets, what will happen is that the liquid water droplets is still warmer than your plastic sheet, okay? Because your plastic wrapping came from the freezer, so it will continue to lose heat and eventually it will freeze to become ice. So, the hint here is that "white solid." So, ask yourself, what could this white solid be? This white solid is actually ice, okay?
So, the first thing would be: Warmer water vapor in the air touches the cooler surface of the plastic wrapping, loses heat, and condenses to water, okay? That is the first part. It must first become liquid water. Then, after that, water loses, because it's already touching the wrapper, so that's fine. Loses heat to the cooler wrapper, plastic wrapper, or wrapping, and freezes to become ice, all right? So, that is your white solid, your ice. Then, after that, they ask you, "How come white solid cannot be seen after a while?" A lot of students say the white solid gently and evaporate. Excuse me, students, this is actually solid. Solid cannot gain heat and straight away become water vapor. It has to melt first, right? What comes after after, uh, when it gains heat for solid, it actually becomes a liquid state. So, you have to say that the white solid, or the ice, which is the ice, gains heat from the surrounding and melts to become water, or liquid water, all right? They did not. So, once this white solid is gone, it's fine.
Now, just to point out one last thing, be very careful. Make sure when answering questions like these, you tell me where is the cooler and warmer surfaces, very important. The next thing you tell me is that, okay, loses heat, and then what is the process? So, the first one is condense. The second is freeze. Also, the last thing is, be very careful when you gain heat or lose heat, it must be from and to where. It cannot be something that you just, you know, just gain heat.