This lesson is called "The effect of sugar concentration on the mass of plant tissue: practical", and is from the unit "coordination and control: maintaining a constant internal environment." Hi there! My name's Mrs. McCready, and I'm here to guide you through today's lesson, so thank you very much for joining me today.

In our lesson today, we're going to carry out an investigation into the effect of sugar solution concentration on the mass of fresh potato tissue.

So I hope you're looking forward to doing a hands-on practical today.

We're gonna cover a good number of key words in our lesson today, and they're shown up on the screen for you now.

You may wish to pause the video to make a note of them, but I will introduce them to you as we come across them.

So in our lesson today, we're going to first of all prepare the practical to investigate effects of osmosis, and then we're going to complete the practical to see what effect osmosis has on the mass of potato chips.

So are you ready to go? I certainly am.

Let's get started.

Now water is essential for life on earth, and every organism requires water for cellular processes to be carried out efficiently.

And plant cells are no different.

In fact, water makes up the substantial part of every cell.

Much of the cytoplasm is water, and then plants also have a vacuole as well, of course, and so have even more water within them.

So water is an important substance within cellular processes, and it can move into or out of cells via the process of osmosis.

So just to remind ourselves what osmosis is, osmosis is the net movement of water molecules through a selectively permeable membrane from a more dilute solution to a more concentrated solution.

And if we look at the diagram here on the screen, you can see that the concentrated solution is where there is more sugar, and the dilute solution is where there is less sugar, and the sugar is represented by those purple hexagons.

So where there is more water and less sugar, the sugar is more dilute, and therefore, because there is more water and less sugar, water will move from that position, down the concentration gradient, to where there is more sugar, where the sugar is more concentrated, and where there is less water, to try and even out the amount of water on either side of the semipermeable membrane.

So this is the process of osmosis, and it's the process of osmosis that we're going to be investigating in our lesson today.

So let's just look at this in a bit more detail then.

If the solution outside of the cell is more dilute than the solution inside the cell, so let's have a look at this diagram.

Outside the cell is in light grey.

Inside the cell is in light green.

Outside the cell, the solution is more dilute.

There is less sugar and more water.

So which direction will the water move? Into the cell or out of the cell? Well, in this scenario, the net movement of water by osmosis will be into the cell, down the concentration gradient from lots of water to less water, from a less concentrated, more dilute solution, to a more concentrated, less dilute solution.

Let's have a look at this in the alternative direction.

So if the solution outside the cell is more concentrated than the solution inside the cell, so if there is more glucose, for instance, on the outside of the cell than on the inside, which direction will the water move in this time? So you should see that it will again move down the water concentration gradient from where there is a lot of water and not very much solute, to a position where there is a lot of solute and not very much water.

In this instance, it will move from being inside the cell to outside the cell, going from the dilute solution inside the cell, where there is only one identified sugar molecule, to outside the cell, where there are plenty of sugar molecules and less water as a result.

So this is the effect of osmosis on cells, and we're gonna investigate the implications of that within our practical today.

So let's just quickly check our understanding though, before we pursue this.

If the water concentration is greater outside the cell than inside, in which direction will water move? Will it, A, move into the cell? B, move out of the cell? Or C, there will be no overall change? I'll give you five seconds to think about it.

Okay.

So you should have decided that if the water concentration is greater outside the cell than inside, then the water will move into the cell.

Well done if you got that correct.

So we're going to investigate the effect of different concentrations of sugar solution on the mass and the length of potato chips.

So in other words, we're going to freshly cut up potato into chips, either circular or cuboid, and we are gonna place them into different concentrations of sugar solution.

So what might the variables be in this experiment? So just remind yourself, the independent variable is the one that we are choosing to change.

The dependent variable is the one that we are measuring.

And the control variables are the ones that we are keeping the same across all of the practical instances.

So what are the variables in this experiment? What do you think? Well, the variables for this experiment are, for the independent variable, the concentration of sugar solution.

We are choosing to change the concentration of sugar solution from a very dilute sugar solution to a much more concentrated sugar solution.

The dependent variable is the change in mass and length.

This is what we are choosing to measure.

So we're measuring the change in mass, we're measuring the change in length, and therefore these are the dependent variables.

And the control variables will be plenty, lots of things that we're keeping the same, such as the volume of the solution that the potato chips are placed in, the time spent in the solution, the length and diameter of the chips to begin with, and the temperature of the solution.

So they are all the control variables that are being kept the same across all of the practical instances.

Now in our experiment today, we're gonna use a range of equipment and materials.

So we're gonna start off with our potato, of course, and from that, using a knife or a borer, we're going to create potato chips.

We are then going to measure the length of them, dry them off using some filter paper, and measure their mass using a balance.

And then we're gonna have a test tube containing water.

We're gonna have four test tubes containing different concentrations of sugar solution.

And we're gonna have a water bath in which to place all of this equipment whilst we're conducting our experiment.

So what do you reckon is gonna happen then? Can you predict what will happen to the mass and the length of the potato chips in the most concentrated solution of sugar? So this is where there's a lot of sugar on the outside and not very much water, compared to perhaps what's going on on the inside of the potato chip.

What about pure water? What happens if we put the potato chip in pure water, where there is no sugar on the outside of the potato, and all water? What do you think might happen to the potato chip in that instance? So what I need you to do when you're predicting what's going to happen is for you to apply your understanding of osmosis to the scenario that you have here, to the effect of the concentration of sugar solution, and the concentration of sugar inside the potato as well.

What do you think that's going to be? How do you think it will compare? And use your understanding to apply it to this scenario.

So let's quickly check our understanding then.

In this investigation of sugar concentration on potato chip mass and length, what is the independent variable? Is it A, the temperature of sugar solution? B, the change in mass and length of the potato chips? Or C, the concentration of sugar solution? I'll give you five seconds to think about it.

Okay, so the independent variable in our experiment today is the concentration of sugar solution.

Remember, this is the one that we are choosing to change.

That's what the independent variable is.

Well done if you got that correct.

So what I'd like you to do now is to prepare yourself ready for this experiment.

So firstly, write down your prediction for the change in mass and length of the potato chips if the potato is sat in distilled water, so that's pure water.

And if it's sat in the most concentrated sugar solution that we're going to use today.

So what do you think is gonna happen to the mass and length of the potato in those two scenarios? And then I'd like you to complete the table to list the variables in this practical.

What are the independent, the dependent, and the control variables? What do those variables mean? And what examples are there from this practical? So pause the video and come back to me when you're ready.

Okay, let's see what you wrote.

So for your prediction, you might have predicted that a potato chip in distilled water will increase in mass and length, and the potato chip in the concentrated sugar solution will decrease in mass and length.

You may well have predicted something different.

That's absolutely fine.

You can keep your prediction as it is, don't change it, and you can review that when we finish the experiment.

And then I asked you to complete the table to list the variables in this practical.

So the independent variable is the fact that we change.

And the example for this practical is the concentration of sugar solution.

The dependent variable is the factor that we are measuring, and in this experiment, it is the change in mass and length of potato chips.

And the control variables are the factors that we are keeping the same.

And this includes the volume of solution, the length and diameter of chips at the start of the experiment, the time spent in the solution, and the temperature of that solution.

So just review your work, make sure you've got a good idea of what's going on in our practical today, and then let's move on.

So now we're gonna move on to actually investigate the effect of osmosis on potato chips.

Now, when we're carrying out this experiment, it's really important that you maintain safety within the lab, for your benefit and for the benefit of everyone around you.

So if glassware breaks, please make sure that it is cleared up carefully, and as soon as possible, and the glass is disposed of in a glass recycling container.

If you spill some solution, it must be mopped up immediately, especially if it is spilled on the floor.

And when you're using sharp knives, they also must be used with caution, and any injuries must be dealt with quickly.

Please use a cutting tile if you are doing the cutting.

And if any of these scenarios occur, please inform your teacher immediately so that they can deal with the situation appropriately.

Now, the method for our practical today is to firstly prepare the potato chips.

You will need five potato chips, and you will remove the skin from each of the ends and cut them squarely to the same length.

Then you're going to dry the potato chips with filter paper.

Do that nice and carefully.

You're just patting them dry.

And then you're gonna measure the length of each of the potato chips, and the mass of those potato chips, and make sure that you record that data.

Then you're going to label five test tubes with one molar, 0.

75 molar, 0.

5 molar, 0.

25 molar, and 0 molar.

That's the distilled water one.

So make sure that each test tube is correctly labelled, and then pour 30 centimetres cubed of each solution or the distilled water into the correct test tube.

So that's your setup.

Then you'll need to place those test tubes into a 30 degree centigrade water bath for five minutes, just to warm up.

And then you can put one potato chip in each of those test tubes.

Make sure you know which potato is going into which test tube, because of course the mass and length measurements will really matter from this point onwards.

And then you're gonna leave those potato chips in the water bath for about 30 minutes.

And then once that's finished, remove the potato chips, pat them dry using filter paper, and then measure the mass and length again.

So take a look at this video just to quickly see how this experiment is going to happen.

Okay, so you will need record the mass and the length measurements in a table.

So make sure that you have an adequate table such as the one on the screen ready to record your results in.

So let's quickly check our understanding.

What I'd like you to do is put these steps of the method into the correct order.

So A is to label test tubes and pour sugar solutions or distilled water into the correct test tubes.

B is to remove each chip, pat dry, and measure the mass and length.

C is to prepare potato chips by removing skin and cutting to the same length.

And D is to place in a water bath at 30 degrees centigrade and leave for 30 minutes.

So put these into the correct order.

I'll give you five seconds to think about it.

Okay, so let's just check our method sequence.

So we should be starting off with preparing the potato chips, then we should be labelling the test tubes, and then we need to place them into the water bath at 30 degrees and leave for 30 minutes.

And then we remove the potato chips, pat them dry, and measure the mass and length.

Did you get those in the correct order? I hope so, because that's what we're gonna be doing today.

Right, let's move on then.

So what I'd like you to do now is to carry out the practical using the method on the worksheet.

And whilst you're waiting for the potatoes in the water bath for that 30 minute slot, I'd like you to explain your predictions using your understanding of osmosis.

So you should have just made absolute outright predictions.

Can you add some detail to them now? And I would also like you to complete the table to describe some of the hazards of this experiment and the safety precautions that you're going to take to deal with any of those risks.

You will also need to record your results in the table, but leave the change in mass and percentage change in mass and length columns blank for now.

We'll deal with them later.

So pause the video, come back to me when you're ready.

Okay, I hope your practical has gone well and you managed to complete all of that fairly smoothly and without too much fuss and stickiness.

So let's just review our work.

So I asked you to explain your predictions using your understanding of osmosis.

So you might have written that the potato chip in the most concentrated sugar solution will lose mass and length.

And your explanation for this is because water will move by osmosis from the potato cells into the surrounding solution, which is more concentrated than the inside of the cells.

Whereas the potato chip in the distilled water will gain mass and length.

And this is because water will move by osmosis into the potato cells from the outside surrounding solution, which is more dilute than the inside of the cells.

So have you explained your predictions with good quality science? If you haven't, now is the time to improve your work and maybe change those predictions if you can't explain, if you can't use the science to fit your prediction.

Well done though.

Then I asked you to complete the table to describe some of the hazards of this experiment and the safety precautions taken.

So for the hazard of broken glassware, the risk is cuts to hands, and the precautions and actions are to clear broken pieces away immediately.

So the hazard of spilt liquids has a risk of slips and falls, and the precautions and actions are to mop up spills immediately.

And the hazard of sharp knives has the risk of cuts to hands, and the precautions and actions are to handle the blade carefully.

So did you get all of those correct? Make sure that you've got adequate risk and precaution actions statements written down.

Well done.

You should also have collected your data within a results table, and you can see some sample data here on the screen.

So I hope you enjoyed that practical and you've got some good data there.

We'll analyse it later.

So we've reached the end of our lesson today.

And in our lesson we have seen that water moves into and out of cells by osmosis, where the net movement is from a more dilute solution to a more concentrated one.

We've also seen that we can investigate the effects of different concentrations of solution on the mass and the length of the potato chips.

We've also noted that it's important to record the start and the end masses and lengths accurately, use our equipment safely, and keep the control variables the same within the experiment to make sure that our conclusions can be valid.

So I hope you've enjoyed our practical today.

Thank you very much for joining me, and I hope to see you again soon.

Bye!.