Lesson Write-Up For Winter Quarter 2013
Your name: Aaron Ferrel
Title of Lesson: How Can a Lake Suffocate a Village? Simulating Lake Nyos
Grade Level: 6th Grade Earth Science
Subject(s):
This topic relates to volcanoes, earthquakes, but also directly teaches density, pH, and
carbon dioxide mixing with water to create acid water. Overall it unites a bunch of
environmental topics taught throughout an earth science class.
Summary:
Lake Nyos is an example of a lake where the bottom is saturated (or near saturated) with
carbon dioxide. This lake is fed carbon dioxide by nearby volcanic activity. A landslide,
volcanic eruption, earthquake or severe windstorm can trigger a quick release of this
carbon dioxide. Since carbon dioxide is denser than oxygen, it will displace the nearby
oxygen, which can turn other bodies of water more acidic and suffocate oxygen-breathing
organisms. Ultimately, the main concepts that the students should learn are that denser
fluids sink, and that carbon dioxide can make water acidic (akin to acid rain), which is
harmful to living organisms. Reviewing volcanoes and earthquakes is secondary, but can
be included to have a bigger component. The students will experience this by
demonstrations generating carbon dioxide in a container with candles, and a lab generating
carbon dioxide in a container with water mixed with pH indicator and fruit flies and
observe what happens. This can be used as a density or volcano lesson.
Time Required: 80-90 minutes.
Group Size: 2-4 students
Cost to implement: Fruit flies: $30, but plenty for weeks. Baking soda: $0.59/3 classes(a
small container), Vinegar: $4/gallon , $22/500 mL (in Fisher scientific for science
education quality grade).
Learning Goals:
After this lesson, students should be able to:
1) Know that baking soda and vinegar create carbon dioxide, a colorless and odorless
gas
2) Explain that carbon dioxide is denser than oxygen
3) Know that when carbon dioxide mixes with water, it makes it more acidic
Level of Inquiry:
Throughout the lesson the students are asked to build upon concepts and surmise
mechanisms for physical phenomena. Initially, they are asked to explain the candle
demonstration, they are given more info and asked again to explain the candle
demonstration. These build into the main lesson and lab where they synthesize
information and come up with conclusions.
Introduction / Motivation:
Start the class with two demonstrations. For the first demonstration, there will be a large
container with three candles at different heights. There will also be a glass with vinegar
placed in the container. Baking soda will be dumped in the vinegar. Students will note that
as the reaction occurs, the candles extinguish with the bottom one going out first and the
tallest one going out last. The students will then individually or with a group discuss
possible reasons as to why this occurred. After this, there will be a water bottle with
vinegar. Then, attach a balloon with baking soda. Once you dump the baking soda in the
vinegar, the balloon will fill up. This is to teach them that the reaction of baking soda and
vinegar form carbon dioxide. Get a balloon filled up with air, and the balloon with the
carbon dioxide. Drop both balloons and ask the students what they observe. They should
notice that the carbon dioxide balloon sinks. After that, ask the students to revise their
hypothesis for determining why the candles extinguished.
Lesson Background Concepts for Teachers:
Density is relevant here. Carbon dioxide is denser than oxygen, so when created in a
container or valley, it will fill the bottom and displace any oxygen. This is what happened
in a village near Lake Nyos. The lake ejected a cloud of carbon dioxide and filled up the
valley nearby, suffocating the village. Additionally, when you mix gases such as carbon
dioxide with water, you lower the pH (make it more acidic). The carbon dioxide cloud
made the lake fairly acidic, making it uninhabitable for fish.
Procedure:
After the introduction, there will be a presentation about Lake Nyos, where volcanic
activity triggered a rapid release of a large cloud of carbon dioxide, which killed a village of
nearly 1700 people and most of the animals around the lake. The presentation will explain
the specific setup and mechanisms for this catastrophe. Finally, the presentation will
identify possible similar locations and specific volcanic and seismic activity that can trigger
an event. The students will then draw diagrams of a lake, and possible trigger mechanisms
(including volcanic or seismic activity. After, the students will do a lab where they create
carbon dioxide in a container but have fruit flies and water with pH indicator in the
container. The fruit flies should be anesthetized and the water should change color to
indicate a drop in pH (that the water became more acidic). A candle can replace the water
and pH indicator if water is not feasible.
Lab Procedure:
1. Draw experimental setup.
2. Fill Container A with 200 mL of water
3. Put 1 dropper of universal pH indicator in the water and stir.
4. Fill Container B with 300 mL of vinegar and place in Container A.
5. Place a container of fruit flies between Container A and Container B so it does not
touch the water.
6. Gently tap the fruit fly container twice.
7. Write down observations about fruit fly activity and color of water.
8. Slowly spoon the baking soda into Container B making sure it does not spill over.
9. Wait one minute and gently stir the water by lifting Container A and slowly sloshing
side to side.
10. Gently tap the top of the fruit fly container five times.
11. Write down observations about fruit fly activity and color of water.
12. Answer questions and draw diagram of experiment.
Materials List
Each group will need:
 Two containers: one large and small, spoon, 60 mL beaker, container with fruit flies,
pipet
To share with the entire class:
 Vinegar, Baking soda, water, pH indicator
Safety Issues:
 No safety issues
Lesson Closure:
The students will answer questions about the lab on the worksheet. Also, they will draw a
diagram of the experiment, showing the direction of carbon dioxide. If time permits, the
class will have a discussion relating what happened in their experiment to what happened
in Lake Nyos.
Assessment:
Pre-Activity Assessment:
The demonstration and ensuing discussion will assess if they know that baking soda and
vinegar form carbon dioxide, and then if they know that carbon dioxide is denser than oxygen.
Although hopefully they can figure it out.
Activity Embedded Assessment:
Throughout the lesson, ask questions that involve the class raising hands to answer. Also,
during the lab, instructor will go around to each lab group and discuss what happened to see
if the students can connect the color/fruit fly activity with the production of carbon dioxide.
Post-Activity Assessment:
Wrap-up questions, and drawings, as well as a class discussion
References:
A video describing Lake Nyos:
http://www.bbc.co.uk/science/earth/collections/worst_natural_disasters#p00gttdw
Description of Lake Nyos:
http://www.geo.arizona.edu/geo5xx/geos577/projects/kayzar/html/lake_nyos_disaster.h
tml
Attachments:
[Please attach your Powerpoint slides, if any, with notes about what you covered in each slide.
Also attach all student handouts and any other relevant materials. Make a list of your
attachments here].
 LakeNyos.pptx
 LakeNyos_LabWorksheet.docx.
List CA Science Standards addressed:
2d. Students know earthquakes, volcanic eruptions, landslides, and floods change human
and wildlife habitats
4e. Students know differences in pressure, heat, air movement, and humidity result in
changes of weather. (for density and pressure)