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Agar gel lab report

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Introduction

AGAR GEL LAB REPORT Aim: to see the affect of the volume is to surface area ratio on the rate of reaction using agar gel. Theory: Agar is a gelatinous substance chiefly used as a culture medium for microbiological work. It is an unbranched polysaccharide obtained from the cell walls of some species of red algae or seaweed. It can be used as a laxative, a vegetarian gelatin substitute, a thickener for soups, in jellies, ice cream and Japanese desserts such as anmitsu, as a clarifying agent in brewing, and for paper sizing fabrics. The word agar comes from the Malay word agar-agar (meaning jelly). It is also known as kanten or agal-agal (Ceylon agar). Chemically, agar is a polymer made up of subunits of the sugar galactose. Agar polysaccharides serve as the primary structural support for the algae's cell walls. Agar is used as an impression material in dentistry. It is also used to make salt bridges for use in Electrochemistry. Apparatus: 1. Agar gel 2. Hydrochloric acid- 60cm3 3. Graph paper 4. Scalpel 5. 3 test tubes 6. 3 beakers- 20cm3 7. Stopwatch 8. Test tube rack 9. Syringe- 20 cm3 Variables: Independent * Volume of the agar gel used for each set of readings. ...read more.

Middle

* After doing this you then measure the dimensions of the agar gel you are using for the experiment. * Therefore, after this you drop each piece of agar gel in each test tube or beaker and start the stopwatch to measure the time taken for the pink colour to disappear. * Therefore after taking the time you rinse the test tube well with water and throw away the used acid, throwing the agar gel away. Results: Formulas used Surface area= 2(hl + lb + bh) Volume= l x b x h Dimensions Volume(cm3) Surface area(cm2) Ratio of volume: surface area 0.5cm x 0.5cm x 0.5 cm 0.125 1.5 1:12 1cm x 1cm x 1cm 1 6 1:6 1cm x 2cm x 2cm 4 16 1:4 0.5cm x 1cm x 1cm 0.5 4 1:8 0.5cmx 0.5cm x 1cm 0.25 2.5 1:10 Ratio of volume: surface area Time taken Reading 1(seconds) Time taken Reading 2 (seconds) Time taken Reading 3 (seconds) Time taken Average (seconds) 1:4 315 333 344 331 1:6 217 206 222 215 1:8 124 135 129 129 1:10 65 71 69 68 1:12 25 26 25 25 Graphs: Analysis and error analysis: From the above results we can see as the Volume: surface area ratio increases the volume and the surface area individually decreases. ...read more.

Conclusion

* The agar gel piece could have broken inside the test tube increasing the surface area leading to inaccuracies. Improvements: There were many errors but these errors could have been corrected and the experiment can be improved by: * More trials could have been taken so that the results would be more accurate and we would also obtain more variety. * We could have used more different kinds of ratios, and then also we would get more varied results. * We should have made sure that the apparatus was in best use so that the inaccuracies would be minimal. * I should have used more beakers simultaneously so that the experiment would be done faster and the results would also be more accurate. * I should have used another person in the experiment that could have helped me in the experiment to avoid parallax errors. * It should have been made sure that the unused agar gel is covered with a lid so that the inaccuracies would also become minimal. * It should have also been made sure that the same apparatus was used and also the same agar gel dish so that the inaccuracies would be constant for all the trials. Conclusion: From the above results, we can conclude that As the Volume: surface area ratio increases the time taken for the reaction decreases. This is because more surface area is exposed and diffusion takes place. Siddharth Nair 10 C 1 ...read more.

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Here's what a teacher thought of this essay

3 star(s)

*** A fairly simple experiment that was well carried out but more thought was needed in the interpretation and analysis of the results.
Planning
The candidate planned a basic experiment but needed to think more carefully about the key control variables.
Carrying out
The student collected an acceptable range of data with a fair number of repeats. The data was presented in a clear and organized way.

Analysis and considering evidence.
A pattern was identified but the candidate seemed to imply a straight line relationship between the variables when this is not the case. There is confusion in the conclusion due to not being clear with the terms used. The rate of reaction and the time taken to diffuse to the centre of the cube are not the same thing. It might have been helpful to calculate the rate of diffusion in all the cubes for comparison. The evaluation concentrates on personal failings and not on the actual method itself. More suggestions for improving the reliability of the evidence would be helpful.

Marked by teacher Stevie Fleming 01/01/1970

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