Experimental Design Lab: Salinization Lab
NAME______________________
Purpose:
To conduct an experiment to determine how the concentration of salt in water affects the germination
rate of seeds.
Background information:
Salt buildup is a potential problem on irrigated farmland in the United States. Much of the world's
unused land is in arid regions where irrigation would be necessary to grow crops. A small amount of salt
in the soil will not affect the germination and growth of crops. However, if salt concentrations increase,
negative impacts occur. Salt concentrations affect the germination of seeds. Farmers need to know the
relationship between the salt concentration and the percent of seeds that will germinate.
Salt kills germinating seedlings by removing the water from their cells. There are several salts involved
in this process. This lab will use sodium chloride (NaCl) as a model. NaCl has a solubility of 35.7 g per
100 mL of water. Ocean water has a concentration of 3.5% which is 3.5 g/100 mL of water. Freshwater
has a concentration of 0.005 % salt which is 0.005 g/100 mL of water.
Procedure 1-Experimental Design:
1. Formulate a general hypothesis, using an If/Then format, from reading the background information.
HYPOTHESIS:
2. Identify the independent and dependent variables.
INDEPENDENT VARIABLE:
DEPENDENT VARIABLE:
3. Identify the control and what should be held constant.
CONTROL:
CONSTANTS:
Materials:
plastic bags paper towels
Distilled water 25 mL graduated cylinder
Electronic Balance scoopula
weigh boat
100 mL Flask
Radish/Squash/Wheat Seeds
stir rod
NaCl concentrations - 0, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 grams/100 mL
Procedure 2:
Your group will be assigned a particular salt concentration to create and collect data from.
Record that salt concentration here _____________ grams/100 mL
1. Using a balance, mass out the amount of salt assigned (____ grams) using the scoopula and weigh
boat.
2. Measure 100 mL of distilled water using a flask. DO NOT USE TAP WATER.
3. Add the solid salt to the flask of distilled water and mix until completely dissolved using the stir rod.
4. Fold a paper towel in half.
5. Slightly wet the towel (with distilled water) to keep the seeds from rolling and place 10 seeds on the
towel.
6. Fold the towel in half and place it inside the plastic bag. Label the bag with the concentration of salt
(______g/100 mL) and a group ID mark.
7. Using a 25 mL graduated cylinder, measure and add 20 mL of the prepared salt solution to the bag.
8. Remove excess air and seal the bag to prevent evaporation.
10. Place the bag in a secure location (wall cabinet or drawer).
11. Check the status of your seeds after several class periods, recording your information in the data
table.
Name of Bag
Number of
Seeds put
in bag
Concentration of
Salt Solution
(g/mL)
Total Number
Germinated
after ___ days
Number not
Germinated
% Germinated =
(# Germinated/#Total) x 100
Control
1
2
3
4
5
6
7
8
9
Graphs: From your data table you should be able to produce two graphs.
1. Construct a line graph on which you compare the concentration of salt solution on the x - axis with
the number of seeds that germinated on the y-axis. Be sure and give your graph a title and label the axes.
2. Construct a bar graph on which you compare the concentration of salt solution on the x-axis with the
% germinated on the y-axis. Be sure and give your graph a title and label the axes.
Analysis:
1. Does there seem to be a relationship between the number of seeds that germinated and the
concentration of the salt water? If so, what is that relationship?
2. Did your experiment support or refute your hypothesis?
3. Can you think of any errors that might have occurred that would invalidate your experiment? If so
what were they and how might they be corrected?
4. Explain why increasing levels of salt concentrations affect seed growth and why irrigation seems to
be the main cause of this. (Use your textbook or research)
5. Do you think all seeds would be affected in similar ways as the ones you used?
6. When soil becomes too salty, what are some methods of remediation?