right today we're going to look at the required practical for osmosis looking at the effect of different concentrations of solutions on some plant tissue our plant tissue being a potato and we'll talk more about the different concentration of solutions in a moment but what I want to do first is prepare my potato my plant tissue to do that we have a cork board this is going to allow me to take samples and potato that are all the same diameter and that's going to important so I can compare my results more easily so here is one cylinder now I'm going to cut three cylinders I'm just going to set up three different concentrations of solution today so one cylinder to cinders and my third potato cinder notice these are all coming from the same potato that should help keep my results more consistent each other easier for me to compare my results with each other now what I want to do now is just going to cut the ends off the ends of these as a potato skin it's going to move those they are impermeable they will not allow water into the tissue that's not what we're looking for this experiment all about water either moving into the plant cells or out of the plant cells and that's really what osmosis is I've now got where cylinders they are all the same length which is vital or approximately the same length so again helping me to compare my results later on but the instructions asked me to measure them into three centimeter lengths so I'm just going to go with that but they are about same length which is fine so the cut each one now I'm only using a ruler here not the most accurate way of measuring these but we'll get will go with it I'll talk about that in a moment I've got one - so that's again three centimeters get getting as close as I can to three centimeters while using a ruler three so I now have three as identical I can get them pieces of potato tissue well I now need to do is measure them very accurately as best as I can I'm going to measure both their lengths using a ruler and also their maths using the top pan balance so the ruler I can measure them and that one is exactly thirty millimeters so they are all exactly 30 minutes millimeters now I need to record those results I need to note sure that I know the length of each sender if they're different they're all the same in this case it doesn't really matter so need to recall those in my results table and then it's away their mass so on this balance what I'm using here is a balance that has two decimal places on it so it is accurate to a hundredth of a gram so I'm using a very high resolution top top and balance here to get very accurate result we're going to see probably very small changes in our mass here which is why we need to use this piece of equipment why it's appropriate and we have a mass of 2.92 grams so I need to record that in my results table having recorded the length and mass this potato cylinder it now go to my boiling tube boiling tube I need to place some liquid into it now I'm going to start with distilled water so this is pure water so it's our first one so the puts in here I'm going to get down level I level of the measuring cylinder so I can very measure very accurately 10 millimeter milliliters of distilled water so go try to keep everything exactly the same between all my expense to help me compare my results there's my distilled water very important and I'll label this so I know what's in here so I can't mix up my samples which would be make it very hard to work out what's happened this experiment it's so hot at the moment I am going to add a bun to this not necessary if we only do this experiment for a short period of time or if the weather is not too hot this will help prevent any evaporation liquid out of the tube so this is my first sample I need to do that for my remaining two cylinders adding 0.25 molar sucrose so this is slightly sugary solution so it's got some sugar added to the water so this is sort of slightly sugary water and I'm going to add to another one 0.5 molar sucrose this is a stronger solution of sugar and we need to see how these three solutions affect the potato now I have set some up earlier I did this yesterday allowing this to run for 24 hours to help my results hopefully increase a bit so it should get bigger results and if I just do it for a short period time so Blue Peter moment income some that I made earlier so I no need to collect my results having left my samples overnight and so we're going to show you how to do that so get my distilled water sample first which is this one now I need to pour away the water I'm going to collect the potato cylinder into a sieve it's off camera but I'm just going to pour it into a sieve it's quite damp it's quite wet wetter than when I first got it from potato so we just remove the excess water on the outside of this that might affect the results quickest way to do that it's very quickly roll it onto the main paper towel it does not want to sit on the green paper towel that could draw liquid out of the tato which would affect my results but I have now removed the excess liquid so now measure my length again I'm using a ruler as I did before and has increased to 32 millimetres length it's an increase of two millimeters there is another piece of clip we could use to measure length called vernier calipers these measure length more accurately so we could use these as an improvement to the expense but we're not going to do that today I now need to measure the mass of my potato after it's being distilled water for 24 hours on to the balance and it is now three point 1/2 grams that is that's actually increased from 2.9 for grams so again we have an increase here in in our results an increase in length and an increase in mass with distilled water these results must be written down in your results table so I've gotta click those results and I need to do the same for the other two solutions so they're 0.25 molar sugar solution again so get pour away the water Claire toss cylinder quickly dry it measure the length it should thirty millimeters no real change there measure the mass which is three point zero six grams which is a very small increase yesterday's result before putting into the sugar solution was two point nine six grams so a very very small increase hit so having measured that one I need to write the results down and move on to my third sample which is the potato left in the strongest solution of sugar naught point five molar sugar solution so again collect my potato cylinder quickly dry on the paper removing excess liquid now I can actually feel this one it's quite floppy compared to the others which gives us a clue as well how results may look in a moment I measure the length hasn't particular changed may have gone down very slightly I can't really tell the actress's ruler so the length may decrease slightly I think that was about thirty millimeters hasn't really changed measure the mass and the mass is now two point six two grams there's a decrease yesterday I measured this at two point eight seven grams so it has decreased in mass so the other two samples so an increase in mass this one has decreased in mass so there's a difference there need to be thinking about why the two different results have occurred so we've now collect our results the next stage is to think about what we can do with that data so you need to calculate the difference in mass and the difference in length from yesterday to today you some of them the mass would have increased and for some of them the mass will have decreasing you to work that out okay so I've measured my length of my cinders yesterday and today I've made my mass my cinders yesterday and today my potato tissue and we've seen this in difference already we need to calculate the exact differences so what I'd like what you now need to do is take your length today your final length and minus the initial length to get a difference has it increased or decreased in length so you may get a negative number just decrease in length you may get a positive number is increase in length so you do the same for all three senators then do the same for mass so again mass today your second mass minus the initial mass and get looking you may get a positive number an increase in mass you might get a negative number a decrease in maths unfortunately because potations were not actually all identical to start now I did try very hard to keep them identical but they were not all the same mass at the start that makes it very hard to compare my results what I need to do is a little calculation that makes it much easier to compare my results a calculation called percentage change so now you've got your change in results you take that change in mass so your mass today minus your initial mass divide it by your initial mass multiply that number by a hundred and you have a percentage change so again if it is increasing mass to have a positive percentage increase and if you have decreasing mass with a negative percentage change and some potato did increase in mass and some did decrease in this nation okay you should be thinking about why that has happened if I did quite a few results more than I've done today you might get a graph that looks something like this so here's a what I've just sketched earlier it's not not particularly accurate but does show you the pattern you would expect to see so you can see here over here we've got a very pure water and our potato should gain a mass and as our concentration of sugar increases so as we add more and more sugar dissolve more more sugar in in the water we increase the sugar concentration you might talk about decreasing the concentration of the water we might see that the results decrease so initially our gaining mass gets less and less and less notice the language i've used there the gain in mass is decreasing we then get a point where our mass may or may not change we might not see that in our experiment but from a line of best fit we can see there's a point where there is no change in mass that's a very useful bit of information this tells you actually how much sugar is within the potato tissue itself though the the water concentration the sugar concentration within the sugar or in the potato is here so we can estimate that by where this line of best fit crosses this axis and then down here so down below this axis we have a loss of mass that is getting bigger and bigger so an increasing loss of mass so the more concentrated sugar the more water the more mass the potato should lose so that's down here so this is what's happening down here and that is osmosis