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The Effect Of Acid Rain On Seedling Germination (page 2)

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Author: Shumit DasGupta

Experimental Procedure

Solutions:

 
  1. Mix 3 parts distilled water with 1 part vinegar to make your first solution. Accuracy in mixing is not the most important part here- measuring the acidity is.2: Use the pH paper to determine the acidity of the solution.
  2. Add either water or vinegar to get the pH to a whole number. It’s easier to add vinegar than water, as you will need less- for instance if the initial mix has a pH of 3.5, it may be easier to add a little vinegar to get the pH to 3 than it would be to add a lot of water to get the pH to 4.
  3. Take approximately 1/10th of your initial solution and mix it with 9/10ths water.
  4. The second solution should be approximately one pH level more than your initial solution. For example, if you got the initial pH solution to 3, than this solution might be 4.2.
  5. Add either water or vinegar to get the pH to a whole number.
  6. Note: you don’t really need to get the pH to a whole number, as long as you are comfortable working with decimals. The goal is to get three solutions with three different pH values. The actual values don’t matter too much, as long as they are at close to I pH ‘point’ in difference. Or even more. Just not to close. Or too far. For example, three good pH’s might be 3.3, 4.7, and 6.0. Three bad ones would be 3.3, 3.4 and 6.9.
  7. Repeat steps 2-5 to get a third solution.
  8. Set aside one solution that is just distilled water to serve as a control for your experiment.
  9. You are now ready to set-up the experiment! 
Set-up 
  1. Count out 40 pinto beans, 40 ziploc bags, and 40 paper towels or napkins.
  2. Label 10 bags for each pH solution with the sharpie, on the outside of the bag. For example, if you have pH solutions of 3, 4, 6 , and 7, you should have 10 bags labled “pH 3”, 10 bags labeled “pH 4” etc. etc.
  3. Place one bean in each of the 40 napkins and place one bean/napkin in each of the 40 ziploc bags.
  4. Add the correct pH solution to each bag, using a different ( or at least cleaned) pipette for each solution. The napkins should be mostly damp throughout, without being saturated- if there is solution collecting at the bottom of the bag, you’ve added too much. Iikewise, if most of the napkin is still dry, you’ve added too little.
  5. Place all the bags in a dark, warm place, like in a cupboard or under the kitchen sink.
  6. In three days, open the bags to take your first data! 
To take data 
  1. On day three, open up your baggies and record the length of all of your seedlings in cm. The first day you open them, they are bound to be very small, if they have even sprouted at all- some may not.
  2. If there is no growth, record the length as 0 cm.
  3. For the remainder of the experiment, measure from the tip of the primary root to the ends of the cotylydons (first leaves).
  4. The seedling is not likely to be straight- place a string against the plant and fit it into all the ‘bendy’ parts. Mark on the string where the seedling began and ended, and straighten the string out.
  5. Place the string against the ruler an measure.
  6. Do this for all plants, and record your data in a table.
  7. Repeat this procedure every two days for 14 days.
  8. At the end, graph your data and draw a conclusion!

You should take show all the data you took during the experiment in a table form. You should also include a graph of growth averages over time- a line graph should do nicely. Any other statistical analysis- percent change, X-squared or t-tests (high school only)- can be added as well, if you know how to do them. 

While no diagrams are required, it is always a good idea to photo document the process so you have great visuals for your science fair board! 

Bibliography

Seed and Seedling diagrams can be found at these websites:
 
 
 
pH strips can be purchased here:
 
 

 

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