• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9

Isotonic Point of Potatoes

Extracts from this document...

Introduction

Aim: To determine the isotonic point of a potato. Research Question: To determine the isotonic point of a potato by placing it in different concentrations of salt (NaCl) solution and measuring the change in mass after a fixed time period. Background Information Osmosis is defined as the movement of water molecules from a region of low solute concentration, to a region of high solute concentration, through a semi permeable membrane, which is one that allows only certain small particles to pass through. A solution with a high water concentration, or low solute concentration is also called a hypotonic solution, and one with a low water concentration is known as a hypertonic solution. When a cell is placed inside a hypertonic solution, water molecules diffuse out of the cell (which has a higher water concentration, or is hypotonic) through the cell membrane, due to the high solute concentration outside the cell. This process is called exosmosis, and it makes the cell flaccid, as it loses water. The very theory can be applied to plants, which causes wilting. When a cell is placed in a hypotonic solution, water molecules diffuse from the solution into the cell, as the solvent concentration of the cell is lower. This causes the cell to become turgid, and it is called endosmosis. Source - http://biosimplicity.webs.com/ A solution which has the same concentration as that of the cell has no concentration gradient as both the cell and its environment have the same water potential. Thus the net movement of water is zero and the system is in equilibrium. Water molecules flow in and out at an equal rate by osmosis, causing the cell size to stay the same. ...read more.

Middle

thin * They had become very soft and completely flaccid * They could bend very easily and became very delicate, thus had to be held carefully * The colour had become very pale, and the cylinders appeared slightly translucent. * The cylinders seemed to be thinner from the centre. Table showing change in mass and percentage change in mass of the potato for each trial of the different concentrations Percentage change = (change in mass/mass before) * 100 Concentration of NaCl solution (M) Trial Mass before (?0.01g) Mass after (?0.01g) Change in mass(�0.02g) Percentage change in mass (%) 0.1 1 1.53 1.80 0.27 17.6 2 1.46 1.77 0.31 21.2 3 1.53 1.81 0.28 18.3 4 1.58 1.90 0.32 20.3 5 1.56 1.87 0.31 19.9 0.2 1 1.53 1.71 0.18 11.8 2 1.53 1.72 0.19 12.4 3 1.51 1.67 0.16 10.6 4 1.41 1.62 0.21 14.9 5 1.42 1.57 0.15 10.6 0.3 1 1.16 1.22 0.06 5.2 2 1.15 1.20 0.05 4.3 3 1.14 1.19 0.05 4.4 4 1.09 1.18 0.09 8.3 5 1.05 1.12 0.07 6.7 0.4 1 0.89 0.84 -0.05 -5.6 2 0.90 0.85 -0.05 -5.5 3 0.82 0.79 -0.03 -3.7 4 0.91 0.88 -0.03 -3.3 5 0.86 0.83 -0.03 -3.5 0.5 1 1.17 0.93 -0.24 -20.5 2 1.13 0.92 -0.21 -18.6 3 1.11 0.95 -0.16 -14.4 4 1.16 0.94 -0.22 -19.0 5 1.12 0.92 -0.20 -17.9 Calculation of average percentage change in mass of the potato Formula used: - Where x is the percentage change in mass; n is the number of trials and is the mean Concentration (M) Average or mean % change in mass 0.1 17.6+21.2+18.3+20.3+19.9/5 = 19.5 0.2 11.8+12.4+10.6+14.9+10.6/5 = 12.1 0.3 5.2+4.3+4.4+8.3+6.7/5 = 5.78 0.4 -5.6-5.5-3.7-3.3-3.5/5 = -4.32 0.5 -20.5-18.6-14.4-19.0-17.9/5 = -18.1 Table showing calculations for standard deviation: Concentration Trial % change in mass Deviation (d) ...read more.

Conclusion

* The temperature or pressure were simply monitored and not regulated, hence a change in temperature or pressure would result in a change in the rate of diffusion, which would in turn affect the final mass. * The surface area of the potato cylinders may not have been equal for all trials as the cork borer may have been pierced in the potato at different angles. * If the potato pieces were not completely dried before weighing then the mass of the residual water on the surface of the pieces (which had not diffused into the potato) would be taken into account. Consequently this would increase the mass of the potato, thus resulting in errors in the results. * Two different potatoes were used as the first potato was not enough to obtain 25 potato cylinders. As a result the isotonic points of both potatoes may have been slightly different. Improvements to the experiment: * The air conditioner and fans should have been switched off while taking readings of mass * Instead to keeping the beakers out, they could have been kept inside a fridge. This would prevent evaporation of water. The beakers could also have been covered with cling film to prevent evaporation of the water. This would ensure that the concentration of the solutions remained constant, and thus the rate of diffusion would not get affected. * In order to make the experiment more accurate, concentrations between 0.1M, 0.2M, 0.3M and 0.4M could have been taken, such as 0.15m, 0.25m etc. This would make it easier to find the exact isotonic point of the potato, and thus the experiment would have been much more accurate. * One potato should have been used in order to maintain a fair test ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Life Processes & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a teacher thought of this essay

5 star(s)

"This is an extremely well written report that contains a high level of detail.
1. The background information is well researched.
2. The variables section contains a high level of detail.
3. The results have been well analysed.
4. The conclusion is complete.
5. The evaluation shows a good understanding of scientific processes.
6. The report is well structured.

Marked by teacher Luke Smithen 01/01/1970

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Life Processes & Cells essays

  1. Marked by a teacher

    Investigate the effect of surface area on osmosis in potato tissue.

    4 star(s)

    I noticed this on both experiments when I weighed the potato with a surface area of 36cm2. The results I recorded were accurate to two decimal places and the readings on the scales were correct because I waited for the reading to settle before recording it on the table.

  2. Marked by a teacher

    "Osmosis" - The Potato Experiment.

    4 star(s)

    This could lead to inaccuracies in the results therefore invalidating them. o I will have to keep the potatoes and solutions at the same temperature (room temperature in this case)throughout the experiment. Equipment A Potato The subject of the experiment.

  1. Marked by a teacher

    An Experiment to determine Water Potential in Potato Tissue.

    4 star(s)

    The result shows that water potential of potato is some where between 0.1 moldm-3 concentration and 0.2 moldm-3 concentrations. Therefore when I do the real experiment I wouldn't bother doing the higher concentration. I will be testing concentrations from 0 to 1.0 moldm-3 every 0.2 moldm-3.

  2. Investigating the effect of changing the concentration of an acid on the rate of ...

    concentration of acid 3 times, and then take an average of the results, after dispelling any anomalies. They are only anomalies if they are more than 10% outside of the other results. To make the experiment a fair test, I will not change any other variables-: * I will check

  1. Osmosis In Potato Tissue

    Firstly, a table, using the headings outlined in "Planning", was set up and the results entered. This table can be seen in Annex 1. To enable us to manipulate and effectively analyse the results that had been formulated, the values in the table were converted into points on a line graph.

  2. Investigation to compare the water potential between potato chips and carrot chips.

    Prediction I predict that as the concentration of sucrose solution increases there will be a decrease in mass. There will be a gradual decrease in mass from a 0.2M concentration up to the 1M concentration. The mass change from the original mass will differ as some values will increase from

  1. An introduction to osmosis.

    If the amount of sugar outside the cell is less than that inside the cell, this means that the solution is hypotonic to the cells of the potato chip. In the first beaker, the water is more sugary than the inside, so the water will come out of the beaker to balance the amount of sugar.

  2. Investigate the effect of temperature on the activity of catalase (from potato)

    The rate of reaction was then converted to the volume of oxygen produced in minutes, by multiplying each gradient by sixty. The two sets of gradients obtained for the graph of each temperature (one for the initial experiment, and the other set of gradients for the graph drawn from the repeat tests)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work