Through
experimentation, students will study the effects of certain
pollutants on plant growth. They will track the growth of
lima beans over a 7-day period, and from the results, can
make connections between our food supply and the importance
of clean water.
Prepare
500 ml each of 4 solutions; salt water, clean water (control),
diluted soap, and vinegar.
Review
concepts of clean water discussed so far. List outdoor water
uses (i.e. watering lawns, gardens, growing plants, washing
cars, water fights, crops, trees, etc...)
3.
Ask students where plants get the water they use to grow (rain,
groundwater, irrigation) and how plant growth would be affected
by pollution.
Context
of the experiment: a local chemical company has been dumping
waste into their back fields and it has been leaching into
a local groundwater source. Local scientists (students) have
been asked to study the long-term effects of this pollution
on local crops (lima beans). Students will compare seed growth
in four different solutions (water, vinegar, salt, and soap).
The water represents freshwater, the vinegar represents acidic
rain, the salt solution represents saltwater, and finally,
the soap represents chemical spills into freshwater supplies
(from residential and factory sources).
Divide
students into lab groups (preferably groups of four). Each
group will receive 4 lima beans, 4 sandwich baggies, and 4
pieces of paper towel.
Ask students to label each baggie, one for each liquid. Students
will soak one paper towel in each liquid and place it in the
corresponding baggie, and they should add 10 mL of liquid.
One lima bean should be placed at the top of each paper towel
and the baggie sealed. Students should puncture each baggie
with one hole at the top and place all their experiments in
the same place in the classroom for observation over the next
7 days.
In
the interim, have students organize their "scientific notes"
(Purpose, Hypothesis, Materials, Observations, Results, and
Conclusions), with daily observation for 7 days maximum.
8.
On a daily basis, students will can record their observations
through drawings, descriptions and measurements of seed or
root growth.
Students can complete
their scientific report by outlining the best environment for
plant growth based on their findings. In their conclusion, they
should make recommendations to the industry in order to save
the local crops.
Conduct a class discussion of the students' results. Did all
the seeds grew? Why or why not? Which seeds grew at the beginning,
and which at the end of the experiment? Why did some seeds
stop growing?
Extensions:
Have
students speculate and research different types of water pollutants,
their causes, and their possible effects on human and plant life.
