Potatoes Cylinders In Higher Water Concentrations example essay topic

Aim: The aim of this experiment is to investigate the movement of water into and out of plant cells by osmosis. The cells chosen for study will be taken from potato tubes as they provide a ready supply of homogeneous material. I did the investigation in two parts, the first part of my investigation was my preliminary investigation and then I did my official investigation. In both of my investigations there are several similarities, such as fair testing, variables, key variables, reliability of evidence and safety precautions. In both of my investigation there were obviously some differences which were in the method, apparatus, results and means of measuring etc.

Essential Background Reading Osmosis is the diffusion of water molecules across a partially permeable membrane from a high concentration of water to a low concentration of water. Movement of substances takes place through the cell membrane, which separates the different substances in the cell from its surroundings. This type of membrane allows small molecules such as water to pass through it, but it denies entry to large particles to pass. This membrane is called a partially permeable membrane. The amount of water inside a cell is called water potential. Turgor is the name given when osmosis takes place between the cytoplasm and the solution outside the cell.

This happens when a plant cell is placed in a high concentrated solution of water, water then passes through the cell wall, the cell membrane, and the cytoplasm and into the vacuole. The increased pressure of water inside the vacuole is called Turgor pressure. Then the cell becomes turgid. Plasmolysis is the opposite of turgor. This happens when plant cells may be placed in a less concentrated solution of water, although this is very unlikely to happen in nature. Water passes out of the vacuole, the cytoplasm, the cell membrane and the cell wall and into the solution outside the cell.

The pressure of the vacuole on the cytoplasm decreases until the cytoplasm pulls away from the cell wall. Diagrams I have illustrated the diagrams of turgor and Plasmolysis on a separate page. Fair Testing This is when the result is only related to the variable being tested. For e.g. if there are six variables, five variables must be kept identically the same and only one is changed / tested to see how this affects the outcome. This is ensuring that this investigation shall only be testing one variable (Key Variable). I have listed the variables below and the key variable.

Variables variable is something, which can be measured or controlled. A dependant variable is the variable you must keep identically the same. I must only test one variable at a time. The independent variable is the one I alter / test. These are my variables: Concentration, this will change from beaker to beaker and will be the main factor that will determine the change in results Size of potato i.e. cross -sectional area of the potato cylinders.

This can change the rate of osmosis over a certain period of time, because if there are two identical potato cylinders but one has a larger surface area over the other then, the rate of osmosis happening over a certain period of time will be much quicker for the plant tissue which has a larger surface area. PH of solution and potato. Same type of potatoes i.e. from the same fields. This could affect the test in many ways, e.g. the ph of the potatoes can vary depending where and how they are grown. Temperature of surroundings. If the beaker is left in a warm place then the water may evaporate and this will change the concentration.

Solvent, my solvent is water. Solute, my solute is sugar Time. The potato cylinders must be kept in their beaker for the same period of time. If not then the concentration will diffuse more or less depending on the time.

My potatoes must be as fresh as possible. If they are left for storage over a long period of time then this may result in the potatoes rotting and then the plant tissue will become faulty. This is because bacteria will start to live on of the potatoes. Key variable This is the variable, which is the most important to the activities outcome.

This will always be the one you change. My key variable is concentration of sugar. Reliability Of Evidence This is proved / validated by repetition of the observation or measurement. For each of the changes of the tested variables (there should be a minimum of 5) each one of the five must be repeated at least once and then the two values averaged. This will also eliminate any human error. If the two results are very different then I must do it a third time to confirm which is a human error.

I will ignore the faulty value and average the two, which are similar in results. I have chosen five concentrations. This will ensure that my results will be accurate as possible. This will also prove that concentration is a factor affecting osmosis in plant tissue, because if the potatoes are in a highly concentrated solution of sugar, then the potatoes will shrink. And if it is placed in highly concentrated solution of water, then the potatoes will increase in size. Safety Precautions When I carry out my investigation I will have to take under consideration some safety precautions.

These safety precautions are very vital, because if I don't take these simple measures in mind then there would be serious danger, not only to my self but also to my other classmates. I must wear safety goggles to protect my eyes from harmful chemicals. After the scalpel has been used I must insert the scalpel into an unused potato, so that there is no danger of me cutting my self or someone else. The scalpel is a razor sharp knife, this is why I must be very careful whist handling it. I must keep my stool under the bench at all times. The stool will obstruct the pathway and this can prove to be fatal.

If this is not carried out, a person passing by may trip over the stool whilst he is holding a piece of equipment, which may endanger him / I must not communicate with any other classmate except from my partner whom I'm working with. I must keep my bag in the cupboard, so that it is not a potential hazard I must always concentrate in the job I'm doing. I must be careful when I'm working and not put any ones life at risk Controlling Factors This is to ensure that any thing extraneous to the experiment (an outside factor) doesn't damage or affect my results. I intend to keep my experiment away from extreme sunlight.

The sunlight will alter my experiment because it will increase the rate of absorption in my water solution. I will make sure that my experiment is thoroughly clean because if it contains samples of substances, which will alter my result, such as hydrochloric acid mixed with water, this can potentially change my results and also make it an unfair test. I will make sure that I use a plant tissue that is homogeneous. It does not contain any seed or pips i.e. it is the same all the way through.

Apparatus will need an apple corer to core out my potato cylinders. This will ensure that the surface area will be the same. I will need 10 beakers, for my solutions. I will need several potatoes, which will be my plant tissue. I will need a table where I can record my results and a pen to write them. I will need a heatproof mat, for safety reasons so I don't damage the bench that I'm going to be working on.

I will need labels to identify my apparatus. I will need a scalpel to cut my potato cylinders to a precise length of 30 mm. I will need four plastic cylinders to measure each of my concentrations, I will use two cylinders to hold 250 ml of sugar solution and distilled water separately. Each cylinder will be able to hold a litre in vol me. I will also have another two cylinders, which can hold a volume of 100 ml each. These will be useful to measure each proportion of solvent and solute.

As this will also be very accurate, which prompted me into choosing this particular apparatus. I will need a ruler to measure the length of my potato cylinders. I have chosen this particular piece of apparatus because it will measure in millimetres. This will prove more to be accurate rather than me measuring in inches or cm. I will need 250 ml of sugar solution for concentrations. I will need 250 ml of distilled water.

I will need a pair of goggles to protect my eyes from harmful chemicals Give A Clear Description Of What You Are Going To DoUsing my scientific knowledge of osmosis, I will try to plan my investigation in as safe, clear and accurate way as possible. The experiment will be done in five concentrations. Saturated solution 40% concentration of sugar 25% concentration of sugar 10% concentration of sugar Distilled water will firstly make sure I have read the safety procedures and then implement them. I will gather all my equipment and apparatus and place them in front of me I will put a heatproof mat in front of me so I don't damage the workbench, when I'm using the scalpel or the apple corer.

I will get my potatoes along with my apple corer and core out 10 potato cylinders and place them in front of me I will then get my ruler and cut my potato cylinders using a scalpel to 30 mm in length. I will insert the scalpel into an unwanted potato after I have used it. I will have to take safety precautions whilst using the scalpel. I will put my potato cylinders aside I will consult a table. This will tell me the proportion and calculations of my concentrations. I made this before the investigation.

I will get four cylinders and label them to distinguish the sugar solution from the water. I will get ten beakers and label them according to the concentrations. I will also have to distinguish my pair of concentrations I will also label them alphanumerically. For example, if my concentration is of a saturated solution of sugar then I will label one beaker sat A, and the other sat B for the second pair of the concentration. I will fill the labelled sugar cylinder with 250 mrs of sugar solution and then place it in front of me.

I will also fill the labelled distilled water cylinder with 250 ml of distilled water I will arrange the beakers in pairs according to their concentrations. I will re-read my table, which I made. The table will tell the exact proportion of solution I will need for each concentration. I will carefully pour 100 mrs of sugar solution into each of two the beakers of my saturated solution. I will then measure 80 mrs of sugar solution and 20 mrs of distilled water and pour the two solutions into each of the beaker.

Which are labelled 40% sugar solutions. I will then measure 50 mrs of sugar solution by using a cylinder and then I will measure 50 mrs of distilled water and then pour the two solutions into each of my beakers, which are labelled 25% sugar solution. I will then measure 20 mrs of sugar solution and then I will measure 80 ml of distilled water and pour them both into each of my marked 10% beakers of sugar solution. I will pour 100 mrs of distilled water into each of my labelled 0% sugar (distilled water) beakers. Before I put the potatoes into the beakers, I will record the time so I know exactly what time I put them in. I will then put the potato cylinders into the concentrations I will place the beaker in a position where it is not too dark or not too bright, after I have placed them I will leave them under investigation, from about 10: 30 am to about 3: 30 pm, Which would be about 5 hrs.

I will come back after five hours and then I will take out the potatoes using a pair of tongs, I will shake the potatoes to get rid of any excess but when I do this I shall make sure I don't lose much of my solution so I will gently shake the potatoes over their beakers, but when I do this I must make sure that I use the tongs gently so I don't damage my plant tissue. I will measure my potatoes one at a time, using a ruler. After I have recorded and measured my results on a table, I will then put them back in there beakers and then I will place the beaker exactly in the same position as before. I will leave them there for another seventy hours for further experimentation's... Methods carried out the experiment according to the information provided in the above plan. The formula I used to obtain the proportions for my concentration: Proportion for sugar = percentage of sugar x 2 The sugar solution contains 50% water and 50% sugar crystals.

This is because the sugar is diluted in water. If I wanted to find for example 30% of sugar, that would be 60 ml of sugar solution and 40 ml of distilled water. The total volume of water of my solution is 100 ml. The reason why I choose distilled water is because tap water has a slight PH of acidity.

This would be an outside factor, which would affect my results, so I have chosen distilled water because it has a neutral PH of 7. Proportion of water = proportion of sugar - 100 ml Prediction Hypothesis: osmosis is described as the net movement of water molecules, where water molecules diffuse from a highly concentrated region, to a region in which they are less concentrated. This movement always takes place across a partially permeable membrane. Osmosis can be explained using the kinetic theory. Molecules of water and sugar are continually moving and bombarding the partially permeable membrane. Occasionally, a water molecule passes through one of the tiny holes from one side of the membrane to the other.

If pure water occupied both sides of the membrane, then equal number of water molecules in both directions until the concentrations will be equal. By using my scientific knowledge of osmosis I hypothesis e that if a potato cylinder is placed in a solution where the concentration of sugar is more than the concentration of water then the potato will increase size / mass, but if I increase the concentration of water this will result in the plant tissue increasing in size / mass more quickly compared. For example if have two potato cylinder and I place each of them in a beaker, but the concentration is different then I would expect the beaker which contains plant tissue of 30% sugar to decrease slightly compared to the plant tissue which decreases more in size and mass because it was placed in a solution of 50% sugar. I also predict after five hours my plant tissue will be affected by osmosis but not as much compared to after 72 hours. This is because water molecules move from a high concentration i.e. the solution, to a low concentration i.e. the plant tissues. Therefore, the potatoes cylinders in higher water concentrations will become turgid and increase in mass compared to the sugar concentrations.

After a certain period of time I predict that the plant tissue will not be able to increase in size any further this is because the plant tissue is completely turgid. And the opposite will happen if I place the plant tissue in a solution with higher sugar concentration than water concentration. I predict that the plat tissue will have become flaccid, and its size will decrease more according to the concentration. This is because osmosis is the diffusion of water from a region of high concentration of water i.e. plant tissue, to a region of low concentration i.e. sugar solution.

After a certain period of time I predict that the plant tissue will not be able to decrease in size any further this is because the plant tissue is completely, this is because no more water can leave the cell.