AP Environmental Science
Soil Salinization Lab
Name _________________________
Per. __________ Date ___________
Background: Soil salinization is a serious threat to agriculture. Excessive salinity costs the United States billions
of dollars each year. As new land comes into use, it is often in arid areas, which are highly susceptible to the
problems associated with soil salinization. Irrigation water contains a variety of dissolved salts including NaCl,
MgCl2, Cacl2, etc. When a field is irrigated, much of the water can evaporate, leaving these salts behind as a thin
layer on top. Overtime, salts build up on fields until the soil is so salty (salinized) that seeds will no longer
germinate in the soil.
In this lab, you will test the following concentrations of salt on mung beans: 0% (distilled water), 0.5%, 1%, 1.5%,
2% and 3%
Problem: How does increasing salt concentration affect the germination of plants?
Hypothesis: (Use the words increasing/decreasing in your hypothesis)
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What is the control in this experiment? ______________________________________________________
What is the experimental group? _______________________________________________________________
What is the independent variable? _________________________________________________________
What is the dependent variable? ____________________________________________________________
What are our constants?
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Materials:
Petri Dishes
Distilled water
Graduated Cylinder
Seeds (mung beans)
5% NaCl solution
Paper Towels
beakers
ruler
Procedure:
Day 1
1. You will test the following concentrations of salt on mung beans: 0% (distilled water), 0.5%, 1%, 1.5%, 2% and
3%
2. You are provided with 5% NaCl solution. You must dilute the solution to make lower percentage salt
concentrations. Use the following formula to determine the volume of 5% NaCl needed for each test. You will
need 10ml of liquid for each test.
Volume of New Solution needed
X
= Concentration of your starting solution
Desired concentration of the new solution
X = The amount (volume) of the starting solution needed to make the new solution
To determine the amount of distilled water needed:
Volume of new solution needed – X = Amount (volume) of distilled water you need to add to make to make the new solution.
For Example: To make 10ml of a 1 percent solution:
10 ml = 5% NaCl solution
X
1% NaCl solution
X = 2 ml of a 5% solution needed.
3. mlWrite
calculations
here
for all your dishes BEFORE going on:
10
- 2 mlyour
= 8 ml
distilled water
needed.
4. Obtain 6 Petri Dishes. Label with the 6 concentrations to be tested.
5. Place 10 mung beans in between two small paper towels in each petri dish.
6. Prepare your 6 concentrations using the math above—remember, you need 10 ml of each concentration.
a. Use the “D” pipet and the “D” graduated cylinder for the Distilled water
b. Use the “5%” pipet and the “5%” graduated cylinder for the 5% salt solution. Do NOT mix these
up.
c. Stir the 5% salt solution before using and pipet from the middle—not the bottom as you will get
too much salt.
d. Pour graduated cylinders into the “Mixing” beaker and swirl to mix
e. Pour over the solution over the paper towels and mung beans. Cover with another small piece of
paper towel.
f. Tuck in the edges of the paper towels into the petri dish or it will dry out.
7. Set your petri dishes in a stack on your lab table (toward the wall)
Day 2
8. Open Petri dishes and observe how many of the mung beans germinated. Record in your data. Figure
percentages.
9. With a ruler, measure the length in mm of each sprout. Record.
Data:
Concentration of
Number of beans
NaCl
germinated
Percentage of
beans germinated
Length of Sprout in
mm
Analysis: Create 2 graphs.
● Graph the relationship between the concentration of NaCl and Percentage of mung beans germinated.
● Graph the relationship between the concentration of NaCl and the length of the sprouts.
Make sure you label your axes and title your graphs (with a phrase or sentence). Make your graphs on a
separate sheet of graph paper and attach.
Lab Conclusion
Write the following conclusion following the Science Writing Guidelines. Use complex sentences in all
sections.
1. Introductory statement with the problem and
hypothesis. ___________________________________________________________________________
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2. Summary of experiment with results. In your summary, ALSO
● Explain whether the results of the lab confirm or refute the hypothesis.
● Discuss the experimental design (dependent variable, independent variable,
hypothesis).
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3. Describe any real or possible error. If you had real error, explain why this error occurred. If no error
occurred, explain why another group had error or theorize where error could occur. Be specific and do not
describe a math error--instead re-do the
math. _______________________________________________________________________________
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4. Paraphrase and cite the textbook or other reference material (pg. #, title and author) and explain
whether the results of this lab confirm or refute the scientific concepts in the
material. _____________________________________________________________________________
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MLA Citation:
5. Provide a concluding statement that is evidence-based (facts and data). Remember, no opinions or
feelings.
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