Intro Quiz: Solubility Practical

Video: Solubility Practical

﻿Hi, it's Ms. Mason here and welcome to today's lesson on solubility practicals. Before we get started, please make sure you've got a pen or a pencil, a piece of paper or a notebook and ideally a ruler. If you need to pause the video to get any of those items, please do so now. Once you've got those, please write down today's title, which is solubility practical, and you may wish to add today's date. Let's make sure all distractions are minimised, so definitely get your phone on silent and have it turned over so that you're not tempted to look at the screen whilst watching this video. Finally, let's remain positive and have a go at every activity, even if it is tough, because the most important thing is to not give up. I'm sure you'd all do absolutely great, let's get started. So as I'm sure a lot of you already know, I like to start off my lessons with a recap. We'll then move on to how we might approach writing a method and creating a results table. I'll write the model to you first, and then you'll be giving it a go. The final part of our lesson, will involve evaluating and concluding, what we found out and then hopefully by the end, you'll be able to write your own method and suggest appropriate improvements to what you suggested. Let's now move on to those recap questions. You've got four questions on the board, all of which have got helpful hints underneath. I'd like you to pause the video now, have a go at these and then restart it once you think you've finished. Take as much time as you need, because I want you to get as many of these right as possible. So question number one to define solubility, you should have said, it's the mass of solid that can dissolve in a 100cm3 cubed of water. Well done if you remembered that. Number two, if a solution is described as being saturated, this means there are no spaces left between the solvent particles, so no more solute can dissolve. Now with flipping back to our chromatography lesson, and if you're asked to write four bullet points on the method for this, so you should have said, draw a baseline at the bottom of a piece of filter paper in pencil. Add samples along this line. Submerge bottom of paper in solvent at the bottom of a beaker and place a lid on the beaker. The solvent will travel up the paper, taking the solutes from each sample with it based on their solubility. And then number four, you should have said, temperature causes an increase in the kinetic energy of the particles, this causes them to vibrate, the bonds between them weaken and they move farther apart. This creates space for more solute to fill and dissolve. Fantastic work, I'm sure you got the majority of those all right. So I'm going to demonstrate to you now how we could investigate solubility. I'm going to demonstrate a little investigation into how many teaspoons of salt I can dissolve in a 100cm3 of tap water before the solution becomes saturated. So, I've measured out, 100cm3 of tap water. I'm going to pour into a glass, just so that it's a little bit more easily visible. Okay, so it doesn't seem like a huge amount, but hopefully we'll get some salt dissolved in that. Okay, so here is my 100cm3 of water on my lovely homemade platform here. And I've also got, some salt, which I'll add teaspoon at a time to this, and we'll see how many teaspoons we can dissolve. So, this is our solute, the salt, and this is our solvent, the water, and by adding them together, we're going to create a solution. So teaspoon number one, let's add that, give it a stir, apologies for any noise, I'll try and stop that. Now, if you want to try this at home, that's absolutely fine, but make sure you've asked an adult's permission and you do have to stir quite vigorously to get the salt to dissolve. But that's just about done, what you want to be looking out for, is if there's any solute kind of floating around on the bottom and I can't see any at the moment, so I'm going to add my next teaspoon. Teaspoon number two. Now, if you were in school, you'd ideally be using a piece of equipment called a stirring rod, which is just a long, thin glass rod, but it's excellent stirring. Okay, we seem to be doing well, that's my second teaspoon dissolved. You can see that the water has gone a little bit cloudier, but the solute has dissolved, so let's go ahead with teaspoon number three. Now, I don't know whether you've noticed, but I've been trying to get, quite an equal sized teaspoon each time I add another one. I don't want to have one teaspoon that's piled up high and then one teaspoon that's got hardly any on it. We want to be adding, almost the same amount every single time to our solvent. So teaspoon number three. Oh no, I think I've done it, so let's go for number four. I've tried to level off the teaspoon each time, which means it's not piled up really high, just kind of nice and flat across the top of the teaspoon. So number four, it's going to happen. I have to say, there's often a lot more than I expected it to. Well, let's go for number five. See if you can make a prediction actually, how many teaspoons do you think I'll manage to dissolve? We're pushing it a bit now. I can see some solute, remaining on the bottom. I might manage to get one more in. We're leading count now, I think this is teaspoon number six. I mean, with my expert stirring, I think we're going to be able to go for teaspoon number seven. You can start to feel when there's excess, so, extra slowly, because, teaspoon feels quite grainy on the bottom. And that's kind of an indication that your solute stopped dissolving. So it might be worth, picking up, the glass and having a look on the bottom. Yeah, so I can see there, don't know whether it's visible on the screen, probably not, but you can see that there was some solute left at the bottom. I'll give it another stir, just to see if I can get rid of it. I think we might have pushed it to the limits now. And what was that word we used to describe a solution when no more solute can be dissolved, can you remember? Saturated. So I think our solution is almost saturated. We might have one more and let's give it a go. Teaspoon number eight, I'm pretty impressed. I wasn't expecting this many. Oh yeah, that's definitely it now, I can see a lot of solute, left on the bottom. Yeah, so, I think we can conclude that in 100cm3 of tap water, we should be able to dissolve about eight teaspoons of salt before it becomes saturated. On the screen, you can see the scientific method for carrying out the practical activity that I just demonstrated. Now, pieces of equipment that you would use in school or in a laboratory setting, are probably not pieces of equipment you're going to have available to you at home. I certainly didn't have available and you will have picked up, that I made some replacements to this method based on what I had available to me at home. So what I'd like you to do, is read through this method, think about the pieces of equipment that you probably don't have at home and what you could replace them with in order for this method to be appropriate in a home setting. So pause the video here, think about the switches that you'd make and then restart the video, to see whether I've come up with the same ones. Okay, so, I have not got a measuring cylinder at home, but I've got a measuring jug. So I would change that in my method. I don't have a small spatula at home, I've got a big one for flipping burgers, but I haven't got a small scientific one, so instead I've put down I'd use a teaspoon. And it doesn't have to be sodium chloride salt that we're using, it could be any sample, so I've just put here in brackets, the chosen sample. And then again, I'm not counting how many spatulas that I did, I'm counting how many teaspoons, because that's what I've got available to me at home. Now, if we wanted to put our results into a table, we need to think about what the most appropriate type of table will be. What do we need in each of our columns in order to display our findings properly? And the table for this kind of experiment should look something like this. The substance in this case, is our independent variable. Okay, so we can change our substance or the solute, to see how different solutes dissolve and our independent variable is what we change and that always goes in the first column of our results table. The second column, always shows the dependent variable, what we measure. And you guys know that we were measuring the number of teaspoons of solute that could dissolve in water in that demonstration, I just did. Okay. So this is what our results table for this kind of practical would look like. And the reason I'm showing you this, is because, I would like you to have a go at a similar practical yourself at home. Before I set you off on your parts collectivity though, I would like you to have the opportunity to plan it. So imagine you are carrying out the experiment I just showed you, on a range of different substances in your home. You need to write a method, describing how you would do this and produce a results table to record your findings. So think about the method and the results tabular I just showed you. And then plan one of your own. You've got some sentence starters to help you, if you want them, but if not, just pause the video, get started and then restart it once you've completed it. Alright, let's see how we got on. So, you should have written a method that looks something like this. Pause the video and read through the points, take off each one that you managed to get as part of your methods, and then compare your results table to the one that is on the screen. Continue watching the video, once you have self-assessed this task. Okay, it's now your turn to have a go at investigating solubility in your home. However, please, please, ask an adult, if you can do this first, because you don't want to go rummaging around in your cupboards mixing things together, if your parent or carer isn't comfortable with you doing that. If they don't want you to do that, that's absolutely fine because I've got some example results ready for you on the next part of the lesson. So just skip ahead to that, if you're not going to have a go at this activity. What I'd like you to do, is similar to the demonstration that I gave you, but just with a range of different solutes. So I've given you some ideas here, you can try and dissolve gravy granules, sugar, coffee, Parmesan cheese. So just get a 100cm3 of tap water. Hopefully you've got a measuring jug in order to measure out that volume and then see how many teaspoons of each of those solutes, you can dissolve in that water. And don't forget to fill in your results table as you go. Pause the video here, have a go at this fun activity and then restart it once you're ready to resume the lesson. So if you gave this practical a go, hopefully you've got your own set of results, but if not, please feel free to use mine, which are on the screen now. Have a look through, these results and then copy and complete the sentences underneath that table. Pause the video here, give that a go and then restart the video once you've done that. Well done for completing those sentences. Now, if we think like a real scientist, then we need to consider things like how we could make improvements to our method. Why are there things that we did that might have affected our results or made our results really different to the results of somebody else? So there were a few things we need to consider. Did we definitely, use, a teaspoon full of solute? And what was the size of our spatula if we were using a spatula? Was it the same, as the size of the spatula that another group used? Did we actually use a teaspoon or did we accidentally use a tablespoon? All of these things could have caused errors in our experiment. How much did we stir each of our solutions? Really, we should have been stirring each of them, the same amount of time, each time we added a tablespoon? So for example, at one tablespoon, stir 10 times, we should have done that for every single one of our solutes in order to keep it the same. And then as well, remember my demonstration, I said about trying to keep a flat teaspoon. Sometimes your teaspoon might have been piled higher than other times, and that would have affected the solubility and how much solute could dissolve. So these are all things that we really need to be thinking about. And we call those, potential errors within our experiment. So within ours, there were three potential errors. Now we've discussed the potential sources of error in our experiment, but what other things could we include to improve our method? I've included three different improvements in this table, but I also need to tell you, why these improvements, could make our data better. So the first improvement I've suggested, is using smaller masses of substance, each time, okay? So instead of adding a whole teaspoon of salt to water each time, or whatever solute you're using, we could add half a teaspoon or even quarter. The reason for this, is because it would allow the saturation point to be more accurately identified. That means, we could be more specific, about exactly when, the solution becomes completely saturated, because it might become saturated, when we add an extra half a teaspoon or an extra quarter of a teaspoon, rather than a whole one. The next improvement, would be to weigh the solvent before and after, so that we can properly calculate the mass of salt that's been added instead of just counting our spatulas or teaspoons. Because if we're able to put, a specific number or a specific mass on it, that's a lot more scientific. It also gets rid of problems, due to differences in spatula sizes. So one might say, okay, I added five spatulas. Someone else might say, oh, well, I managed to add seven. And that might be, because we use different size spatulas. So, if we could get a value for the total mass of the solute that we added, that would provide, a much more accurate, result. Finally, I've said about adding a magnetic stirrer. Now I'm not suggesting that anybody has a magnetic stirrer at home, and it's not even that likely that you'd have a magnetic stirrer at school. But if you did, this would just make sure, that the solution was stirred consistently and that all solutions were stirred the same. I appreciate that I've just thrown quite a lot of information at you there. So I'm going to put you through a series of multiple choice questions, to see what you've managed to pick up. First one, which of the following is a potential source of error in this experiment? So the experiment that I demonstrated, where I added teaspoons of a solute to water and the one that some of you might've had to go up. You can pause the video here, to read through the options and then restart it once you're ready to find out the correct one. So the potential source of error in this experiment is, inconsistency in stirring. Okay, so not stirring all of the solutions the same, that's definitely a potential source of error. Next up. Why would using a magnetic stirrer in our method, improve the data we collect? Pause the video, read through the options and restart it, once you think, you know the answer. The correct answer should have been, option number one. A magnetic stirrer allows consistent stirring, so all solutions will be stirred equally. Next up, in our method, why would adding smaller masses of substance each time improve the data we collect? Again, pause the video, decide which option is right, and then restart it. The correct answer was option two. If we add smaller masses of substance each time, this allows the saturation point to be more accurately identified. Massive well done if you remember that. One more question to go. In our method, why would measuring the mass of the solvent before and after adding the solute improve the data we collect? Final video, pause, on this section. Choose the right answer. Restart to find out if you've got it. Option four was the correct answer, so measuring the mass of the solute before and after gets rid of problems due to differences in spatula size. Well done, that was tricky stuff, you're doing so, so well. What I would like you to do now is produce a piece of writing, on the potential sources of error in our experiment and the ways in which we could improve our methods based on the last few things I've talked to you about. So pause the video here, read through the description again in the white box, and then use those sentence starters, to help get started. Restart the video once you think you're done and we'll go through what the perfect answer would look like. So let's start off by going through the potential errors in this experiment. What did you remember and what did you write about? The potential areas are in pink. You might want to pause the video again, read through the three potential errors and either tick or add, these errors onto your answer. Okay, moving on to improvements to the method. Again, I'm not going to read through all of this because I've talked about it a lot, but just pause the video, read through yourself, tick and then if you manage to get, and add anything you didn't quite get. Before we finish the lesson, I just want to run through one other potential investigation opportunity we perhaps would have taken, if we were in school, in a laboratory setting. So as an alternative experiment, we could have changed up the solvent we were using as opposed to the solute, like you did in your experiment or my demonstration. So for example, we could have used water as the solvent to see how many spatulas of teaspoons of a solute would dissolve. And then we could have tested the same kind of thing out, but with ethanol as the solvent. So, looking at this results table, I'd like you to consider, the questions that appear underneath where it says conclusion. So does the solvent affect the solubility of the solute? Look at the results table and make your mind up. And it asks you, how you know that? So you will need to take evidence from the results table to use in your answer. The question underneath that, asks if the results are reproducible and how this could be checked? Now, I'm not going to tell you what that means yet, because I'm hoping some of you might already know. So I'd like you to pause the video, have a go at answering those questions and then restart it when you're ready for me to go through the answers. Okay, so you should have said, yes, the solvent does affect the solubility of the solute. Because one solvent, water, was able to dissolve, more of the solute than the other solvent. And you could have actually said, because water dissolved eight spatulas of solute, whereas ethanol only dissolved five spatulas. Well done, if you included something like that. Now the word reproducible, that means, could somebody else use the same methods that we used to get the same results? Now, if they were able to get the same results from using the same method, then yes, the results would be reproducible. If not, and they got something totally different, then we'd have to say, no, the results are not reproducible. But in order to determine the reproducibility, we have to compare our results to the results of somebody else that's done the experiment in exactly the same way. That brings us to the end of today's lesson. And if you'd like to, please ask your parent or carer to share your excellent practical work on Instagram, Facebook or Twitter, tagging @OakNational and #LearnwithOak. Please exit this video and complete the exit quiz in order to review what you have learned today. Thank you so much for joining me and I can't wait to see you again soon. Bye bye.

Worksheet: Solubility Practical

Exit Quiz: Solubility Practical

Completed: Solubility Practical

This lesson looks at how we can investigate solubility, potential sources of error in investigations and identifying ways in which can improve our method.

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Solubility Practical

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