Activity—CO2 Gas and Candles

Activity—CO2 Gas and Candles
Create an invisible odorless gas to snuff the candle “villages”.
This Demonstration uses candles of varying
heights to demonstrate the hazard of volcanic
gases. Put 3 stubby candles of varying heights
into a steep-sided bowl to mimic 3 villages
of varying elevations in an enclosed valley.
Make CO2 gas using baking soda and vinegar.
Next slowly pour the gas from the vinegar mix
into the bowl of lit candles. The candles are
progressively extinguished from shortest to
tallest as the level of CO2 gas in the bowl rises.
The Student Activity called, “What Happened
at Lake Nyos” with student worksheets and
teacher answer sheets was developed by Chris
Hedeen (Oregon City High School, Oregon).
Science Standards
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Systems
Inquiry
Evidence of Change
Forces and Motion
Energy & Matter: Transformation and
Conservation
Cycles in Earth Science
Predictability & Feedback
Additional Resources relevant to this activity
Poisonous volcanic gas video demo
Background:“VolcanicGasesandTheirEffects”http://volcanoes.usgs.gov/hazards/gas/index.php
Note: The activity on the following pages (used with permission) is from Volcano Video Productions,
fromtheirTeachers Guidetotheaward-winningDVD:
Lava Flows and Lava Tubes; What They Are, How They Form
Activity —CO2 Gas & Candles
1
3-4: CO2 Gas & Oxygen Deprivation—Silent Killer
Lab Demonstration
Introduction
Carbon dioxide (CO2) is present in volcanic gas. It is invisible
and odorless and is one of the major pollutants in the atmosphere, so it is critical we understand the hazards. Because CO2
is heavier than air it can be deadly when concentrated in low
lying areas. This inquiry-based demonstration shows how CO2
gas produced from vinegar and baking soda displaces oxygen
and sequentially snuffs candles representing different elevations.
The optional exercise uses dry ice to introduce change of matter
from solid to gas as the ice sublimates, not passing through a
liquid phase as H2O ice does, under normal pressure conditions.
Objectives—Students will:
• Learn about the toxicity of carbon dioxide;
• See how carbon dioxide collects in low-lying areas;
• Learn how to escape high carbon dioxide concentrations.
Overview of Carbon Dioxide Gas
Volcanic gases like carbon dioxide, sulfur dioxide (SO2),
hydrogen sulfide (H2S), and water (H2O) bubble out of magma
as it rises to the surface. (See Activity 3-2, 2nd paragraph of
the section on Why the Vinegar & Soda Reaction is NOT Like
the Expansion of Gases in a Volcano. See also, Gas Drives an
Eruption in Activity 3-1.)
The following is from a USGS publication on volcanic gas.
Volcanoes release more than 140 million tons of CO2 into
the atmosphere every year. This colorless, odorless gas
usually does not pose a direct hazard to life because it
typically becomes diluted to low concentrations very quickly whether it is released continuously from the ground or
during episodic eruptions. But in certain circumstances,
CO2 may become concentrated at levels lethal to people
and animals. Carbon dioxide gas is heavier than air and
the gas can flow into in low-lying areas; breathing air with
more than 30% CO2 can quickly induce unconsciousness
and cause death. In volcanic or other areas where CO2
emissions occur, it is important to avoid small depressions
and low areas that might be CO2 traps. The boundary
between air and lethal gas can be extremely sharp; even a
single step upslope may be adequate to escape death.
There is normally between 300–500 ppm (0.03–0.05%) CO2 in
the atmosphere. Greater than this amount is considered pollution.
The toxicity of CO2 is due to oxygen deprivation. At 2-3% in
the air you might not notice it but just be short of breath. At 7%
symptoms include headache, shortness of breath, dizziness, loss
of mental ability, weakness, and ears ringing. At 10% you lose
consciousness within 10-15 minutes. Above 15% is lethal.
Again, the release of CO2 from volcanoes (from vents, the
ground, and lava flows) are particularly hazardous because:
(1) there is often little warning of high concentrations;
(2) it is odorless and invisible; and
(3) CO2 is heavier than air so it collects in topographically low
and/or poorly ventilated places.
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Activity Length
10 minutes, plus discussion.
Materials
Additional activity and
student worksheets &
answers begin on PAGE 3.
• Vinegar.
• Baking soda.
• 8- or 16-oz glass meas. cup with pouring lip (16 is best)
• Soup bowl with room for three candles (photos on 3rd page
of this activity).
• 3 candles (1/2, 1, and 11/2 inches high).
• Optional Activity: dry ice (solid CO2).
Resources
Description of Gas and gas sampling on page 121
For good description of gas hazards go to the folders:
3. Fact Sheets> 6. Volcanic Hazards > 2. Gas From Volcanoes
Quicktime movie of the activity on next page and in folders:
Educational Resources> 2. Movies of Activities >
EX.3-4_Invis.Gas.mov
Deadly Incidents of CO2 Poisoning
Nearly two thousand people have died of carbon dioxide asphyxiation near volcanoes in the past two decades, most of them
in Cameroon, Africa, and in Indonesia. Recently there have been
cases of near asphyxiation from carbon dioxide emissions at
Mammoth Mountain, a young volcano on the eastern front of the
Sierra Nevada mountains in central California [box next page].
Lake Overturn: The most disastrous CO2-related incidents
have occurred near lakes that have very high levels of CO2
at depth. On August 12, 1986, Lake Nyos, Cameroon, had
a sudden release of about 1 km3 of CO2 gas. Before this,
the CO2 was held under pressure at the bottom of the lake.
In warm climates, lakes easily become stratified. If Lake
Nyos had been in a colder climate regime the water would
have “turned over” once or twice a year due to cold ice melt
sinking to the bottom of the lake. The abrupt overturn of
Lake Nyos resulted in the upwelling of high concentrations
of CO2 gas that flowed downslope away from the lake and
pooled in nearby villages, killing at least 1,700 people and
thousands of animals by asphyxiation. The high density of
cold CO2 gas relative to the ambient air allowed the gas cloud
to flow down topographic depressions and accumulate in low
areas.
Volcanic Gas Emission: An eruption in 1979 on Dieng Plateau,
Indonesia, was the worst known eruption-related CO2
tragedy. About 142 villagers were hiking away from a small
eruption when they entered a low area along the road. Carbon
dioxide gas from the eruption had accumulated there. They
were found lying down, still in line, along the road. People
in the rescue party also died when they went to retrieve the
bodies.
Teacher’s Interactive Resource Guide to the Video “Lava Flows and Lava Tubes”
TOTLE workshop
Grade Level: 5-12
NSC Standards: A, B, D, F
Used with permission from www.volcanovideo.com
Instructions
Optional Dry Ice Activity
1. Talk to the students about the role of CO2 in the atmosphere.
Aside from exhaling, where else is CO2.produced? (See text
box on next page.) Tell them that you are going to show them
how an invisible gas can deprive an area of oxygen. You
can’t see it or smell it. Candles are used in mines to detect
low oxygen levels; when CO2 replaces oxygen, the candle
will first flicker, then go out.
2. Place the two or three candles in the bottom of the bowl
(photos on next page). Make sure all students know the
safety rules for fire. Light the candles.
3. Pour 1/4 cup of vinegar into measuring cup. Cover all but the
pour spout with plastic wrap.
4. Add a teaspoon of baking soda. Let it bubble for a bit.
5. Tip pour spout over the bowl, careful not to let any bubbling
mix spill out. Any gentle breeze will blow the gas away, so
do this in a still room. Though invisible, the newly formed
heavy gas will pour into the bowl, rising until first the
shortest, then the tallest candles flicker, and then go out.
6. Have the students record their observations.
• What is going on? (Flames need oxygen for combustion.)
• Point out that this gas is the same one which living things
respire (breathe out)...so how can it be poisonous? [It is
replacing the oxygen that we need to breath in.]
• What would happen if you were locked in a sealed room?
• What would you do if you knew that there was CO2
accumulation? [Go to a higher place.]
• Where is the safest place in this town?
A similar exercise can be done with dry ice (solid CO2),
which sublimates (changes matter from solid to gas) to
produce CO2 gas. To produce dry ice, the gas is chilled to
below -78.5° C (minus 109°F!). It turns to vapor directly
from the solid state, never passing through a liquid phase
like H2O ice does. Note: H2O ice sublimates in freezing conditions; witness the depleting ice cubes in your
freezer.
Make sure that students understand the danger of dry
ice: it can freeze skin if it is in contact for more than a
few seconds. The freeze is essentially a burn.
This exercise can be done as a demonstration, in pairs
or small groups. If pairs, give each pair of students a
one- to two-inch piece of dry ice, a paper cup, and a piece
of plastic wrap. Seal the ice in the cup with the plastic. As
the gas sublimates off the solid CO2 it should inflate and
then force the plastic off.
The gas produced can then be poured into the bowl with
the candles. Have the students write down what they saw.
The effect will be much more dramatic with water in
the measuring cup with the dry ice. It will look like the
water is boiling, but the bubbles are the CO2 gas escaping
through the water. In this case, the bubbles are visible, but
remember that the gas is invisible.
Have the students blow gently into the cup as the water
is bubbling. They will then see what looks like steam.
This is the H2O (steam) in their breath vaporizing against
the cold ice.
Invisible CO2 Gas Killing Trees at Mammoth Mountain, California [from USGS Fact Sheet 108-96]
CO2 gas seeping from the ground at Mammoth Mountain likely was derived from magma (molten
rock) beneath the volcano. In 1989, rising magma may have opened cracks, allowing large
amounts of trapped CO2 gas to leak upward along faults. High concentrations of CO2 in soil can
kill the roots of trees. CO2 gas is heavier than air, and when it leaks from the soil it can collect in
snowbanks, depressions, and poorly ventilated enclosures, such as cabins and tents, posing a
potential danger to people.
The rest of this document can be found on this CD in the folder:
3. Fact Sheets> 6. Volcanic Hazards > 2. Gas From Volcanoes > CO2 at Mammoth.pdf
or on the internet at http://quake.wr.usgs.gov/prepare/factsheets/CO2/
In March 1990, a United States Forest Service ranger became ill with suffocation symptoms after being in a snow-covered cabin near Horseshoe Lake. Measurements taken
near Horseshoe Lake found a deadly 25% concentration of CO2 in the cabin.
Used with permission from www.volcanovideo.com
In 1989, trees in this area on the south
side of Mammoth Mountain volcano
began dying from high concentrations
of CO2 gas in the soil. Although leaves
of plants produce oxygen (O2) from CO2
during photosynthesis, their roots need to
absorb O2 directly. High CO2 concentrations in the soil kill plants by denying their
roots O2 and by interfering with nutrient
uptake. In the areas of tree kill at Mammoth Mountain, CO2 makes up about 20
to 95% of the gas content of the soil.
Section 3—Activities Beyond Lava Flows
Activity —CO2 Gas & Candles
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About Global Warming and Volcanoes
Yearly averages of global temperatures have
steadily increased since the mid-1800s when industrial and automobile contributions to CO2 n the
atmosphere increased. Although CO2 is abundant
in volcanic gases, it should not be considered as a
contributor to the greenhouse effect. The sum of Earth
and solar processes created the conditions that are
hospitable to life as we know it. Humans activities
may be disturbing that balance.
Comparison of CO2 Emissions—
Volcanoes vs. Human Activities
We used 3 candles in this exercise. Each represents a topographically higher position in this bowl “valley”. [An option is to
construct a clay or mud mountain in the bowl with the candles
exposed to represent towns at different elevations.] The tallest
one should have the candle lip at bowl height with the flame
above the lip of the bowl so it won’t be extinguished by the CO2.
The candles stay lit because the oxygen in the room is evenly
distributed.
A 2-cup clear measuring cup works better than the 1 cup shown.
Begin by adding a teaspoon of baking soda into 1/4 c. vinegar
and let it bubble for a moment. CO2 gas that is being produced
is collecting above the liquid. When you are sure it won’t bubble
over the top carefully tip the spout over the edge of the bowl.
Don’t let the bubbles spill into the bowl.
Scientists have calculated that volcanoes emit
between about 145-255 million tons of CO2 into the
atmosphere every year (Gerlach, 1999). This estimate
includes both subaerial and submarine volcanoes, in
about equal amounts. Emissions of CO2 by human
activities, including fossil fuel burning, cement production, and gas flaring, amount to about 26.6 billion
tons. Human activities release more than 150 times the
amount of CO2 emitted by volcanoes—the equivalent
of nearly 8,000 additional volcanoes like Kïlauea
Volcano on the Island of Hawai‘i. Kïlauea, which is
pumping gas out like crazy during the current eruption
that began in 1983, emits about 9370 tons per day!
Volcanoes produce an amount of CO2 that is less than
1% of that produced by mankind.
(From Terry Gerlach, US Geological Survey)
The lowest candle should extinguish fairly quickly. As the gas
level rises in the bowl the second candle will go out. The third
candle, if it is at the level of the bowl rim, will grow a little weaker
as the gas rises over the rim, but it won’t go out.
Watch videoClick
in activity
folder: PoisonGas_Demo.mov
on image
to play video
NPS photo of gas billowing from
Kïlauea Volcano, Hawai‘i.
Want to calculate how many Kïlauea volcanoes would
equal the amount of CO2 humans produce every year?
(human CO2 output)
26,700,000,000 tons/year
= 7, 800 Kïlaueas
(9,370 tons/day) * (365.25 days/year )
(Kïlauea CO2 output) (to account for Leap Year day)
For more about global warming see folders in the files:
3. Fact Sheets> 6. Volcanic Hazards > 2. Gas From Volcanoes
or go to the following websies
http://www.epa.gov/globalwarming/kids/
http://www.ncdc.noaa.gov/monitoring-references/faq/global-
Again, it is important that the foaming mix NOT pour over the lip
of the cup. Only the gas that is accumulating above the foam is to
be poured invisibly down the edge of the bowl.
http://globalwarming.sdsu.edu/
[33 facts about warming]
http://www.nrdc.org/globalWarming/f101.asp
Teacher’s Interactive Resource Guide to the Video “Lava Flows and Lava Tubes”
From the Teacher’s Interactive Resource Guide to the DVD:
Lava Flows and Lava Tubes: What They Are, How They Form. Available at www.volcanovideo.com
TOTLE workshop
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warming.php
Name: _________________
Per: ____
Date: _________________
What Happened at Lake Nyos?
Lake Nyos is a deep maar lake of explosive origin in northwestern Cameroon. Nyos is infamous, owning to a catastrophic release of carbon dioxide gas on the
evening of August 21, 1986 that killed an estimated 1700 people and 6,000 head
of livestock in the valley below.
The Lake’s Geological History
Lake Nyos is in the hilly grasslands of western Cameroon, within the so called Cameroon
volcanic line: a string of volcanoes that extends 1600 km from the South Atlantic Ocean to the
northeast, along the border of Cameroon and Nigeria. Nyos is a classic maar, formed in a coarsegrained biotite-quartz monzonite about 4,000 years ago. Lake Nyos has an area of 1.49 km2, 208
meters deep, and has a water volume of about 132 million cubic meters.
Carbon dioxide is the main gas that escapes from the earth’s mantle, which is also the source
of magma, or molten rock, that erupts from volcanoes. The carbon dioxide had chemical
characteristics indicating that it could only have come from the earth’s mantle (the layer of
the earth that underlies the forty-mile-thick crystal rocks). The gas was gradually seeping into
the bottom of the crater lake from fractures and faults in the neck of the old volcano and had
accumulated in the lake over several hundred years.
There are two potential sources for the gas released: volcanic and magmatic. Because of undisturbed sediment, clear deeper
waters, lack of temperature increase, and the absence of other chemicals (sulfur and chlorine compounds), it appeared that
no major volcanic eruptions had occurred in the lake. Scientists then concluded that much if not all of the carbon dioxide
released was of magmatic origin, which was dissolved in the cold, deeper lake water prior to the event. Lake Nyos is also
strongly stratified – the lower denser water and less dense upper water generally do not mix. This condition led to further
buildup an entrapment of carbon dioxide in the lower water.
As the gas saturated lower water rose to the surface, the gases rapidly came out of solution; decreasing pressure allowed
bubbles to form, just as when a bottle of soda is opened. The eruption spewed a column of water and gas over 80 meters into
the air. Because carbon dioxide is denser than air, it flowed down the mountainside into a populated valley below, causing the
residents of the area to lose consciousness and quickly die of asphyxiation.
Although it is not clear what finally triggered these events, possible causes
include a heavy rain, strong winds, an earth tremor, a landslide, or a seasonal
change in the layers of the lake’s water – any disturbance that may have
moved the deeper, gas-rich waters closer to the surface. With the overlying
pressure reduced, there was nothing to keep the gas in solution. Bubbles
formed and rose rapidly, dragging additional deep water toward the surface
and depressurizing it. This process led to a chain reaction, which produced
a sudden and violent release of carbon dioxide gas, estimated to have a
volume 0.68 km3 – 1.00 km3.
Define the following terms:
Stratified Lake:
Saturated:
Asphyxiation:
Activity —CO2 Gas & Candles
5
Part A: Properties of CO2 — Floating Bubbles, Sinking Gas
Materials:
1000 ml beaker, vinegar, baking soda, and bubble solution with wand.
Procedures:
Produce CO2 gas by placing approximately 2 tsp. of baking soda in the 1000 ml beaker. Add 200 ml of vinegar and
observe rapid bubbling.
+
-
NaHCO3 + HC2H3O2
Na + C2H3O2 + CO2 + H2O
After the bubbling has stopped, use a bubble wand to blow bubbles into the air.
Pick up the beaker and gently try to catch a bubble within the container. Do not blow into the container, as this will
disturb the carbon dioxide present. What did you observe?
Describe some of the physical properties of CO2.
How did the carbon dioxide gas kill the people in the valley below Lake Nyos? Relate your response to the experiment?
Part B: Velocity of the CO2 Cloud
Materials: Ring stand with clamp, four tea candles, 3.8 liter container, 1.5 m rain gutter,
stop watch, 2 tsp baking soda and 200 ml vinegar.
Procedures:
Secure one end of the rain gutter 30 cm high on the ring clamp.
Place one candle at the top edge of the ramp and one at the bottom. Distribute the remaining two candles between the
upper and lower candles.
Place 2 tsp. of baking soda in the 3.8 liter plastic container. Add 200 ml of vinegar, cover with paper.
Light all four candles. Slowly pour the CO2 into the elevated part of the gutter. Don’t pour any liquid into the rain gutter.
Record the time it took the CO2 to travel down the 1.5 meter ramp.
Repeat steps 3 – 5 using the remaining CO2.
Distance
Time
(m)
What did you observe?
How do you know CO2 was present? Explain.
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TOTLE workshop
1
(s)
Explain how the flow of the carbon dioxide in the experiment relates to the topography surrounding Lake
Nyos.
In relation to the Lake Nyos Disaster, explain why there were no casualties 100 meters above the surface of
Lake Nyos (elev. 1101 m).
Calculate the two velocities (m/s) of the CO2. Show calculations.
V1= ________________
V2= ________________
Explain why V1 was faster than V2.
The estimated velocity of the Lake Nyos CO2 cloud flowing into the valley was 20 m/s. How did your calculated
velocity compare to the velocity of the Lake Nyos CO2 cloud?
Explain why there is a difference between the estimated velocity of the Lake Nyos CO2 cloud and your
calculated velocity.
Analysis (Use complete sentences for full credit)
1. Carbonated beverages contain dissolved carbon dioxide. When you open a bottle, bubbles begin to appear
as the gas comes out of solution. Explain why this happens and relate it to the Lake Nyos disaster.
2. Was the source of CO2 that was stored in the depths of Lake Nyos magmatic or volcanic? Explain why.
3. Air is composed of 78% nitrogen (N2) and 21% oxygen (O2). Calculate molecular weights of these two gases
and carbon dioxide (CO2) and suggest a reason why the carbon dioxide might have a greater density than
air. (Use the periodic table to calculate the molecular weights.)
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Activity —CO2 Gas & Candles
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4. Explain why the CO2 stayed in solution and was confined in the lower depths of Lake Nyos over a period of
several hundred years.
5. List three possible events (a – c) that may have triggered the upwelling of the lake’s waters.
a.
Supporting evidence:
Arguments against:
b.
Supporting evidence:
Arguments against:
c.
Supporting evidence:
Arguments against:
6. Choose one of the above hypotheses to be evaluated.
Which hypothesis is being evaluated?
Are there elements in this hypothesis that are untestable? Explain.
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TOTLE workshop
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Teacher answer key
Activity —CO2 Gas & Candles
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Activity —CO2 Gas & Candles
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