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Acid Rain Demonstration (Burning of Sulphur) –
An Environmental Connection
««« By Leila Knetsch
Leila Knetsch is the ACL of Science at Albert Campbell CI. She is currently interested
in incorporating literacy and technology into science. Leila may be reached at
[email protected].
Curriculum Connection: Grade 9 Science (Ecosystems Unit or Chemistry Unit),Grade 11 U Chemistry
(Types of Reactions or Solutions Unit /Acids and Bases), Environmental Science.
I have shown this demo for Grade 9 and 10 Science for a variety of reasons.
Reference: An unknown Grade 11 General Chemistry textbook, no longer in use.
Introduction
Although I no longer remember from where it originated, this demonstration is one of my favourites. Generally, you
burn sulphur to make sulphur dioxide and allow the sulphur dioxide gas to dissolve in water to form sulphurous acid
like in acid rain. If you have a good sense of the dramatic, when you shake the gas bottle, the water turns suddenly from
blue to yellow. The students enjoy the dramatic and unexpected change. I love that it can be used at different points in
the curriculum for different reasons (see above) and that it connects to the production of acid rain. There are loads of
extensions, too. I sometimes would follow this demonstration with a reading about acid rain and have my students
connect the reading with a literacy task (i.e. Think Pair Share, or TGT), or do a co-operative learning activity with it. Or
you could have it lead in seamlessly to a laboratory activity where the students can see the impact of an acid on
limestone (calcium carbonate) at different concentrations to mimic the damage to limestone buildings or erosion of
limestone around Ontario. I did this in grade 10 Applied Science a number of times.
Safety concerns
The sulphur is burned to form sulphur dioxide, which is an acrid white smoke. This demonstration should be done
in the fume hood. Disposal of the resultant sulphurous acid can be done by pouring it into a hazardous waste container
for pick up or react it with a base such as sodium hydroxide and neutralizing it prior to pouring it down the drain.
Apparatus
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Deflagrating spoon
Powdered sulphur
2 gas bottles with 2 flat glass plates to go across the top
Water
BTB indicator (bromothymol blue)
Large Bunsen burner
Acid Rain Demonstration
• Safety goggles
• Lab coat
Volume 44 • 4 April 2013
CRUCIBLE online
www.stao.ca
Method
1. Before you start the demonstration, turn on the room exhaust and the fume hood. This demonstration should
NOT be done in a room without a fume hood and cannot be done outside.
2. Fill the gas bottle halfway full with water. Add bromothymol blue (BTB) to the water. It will turn the water blue
(BTB is blue in neutral and basic solutions but yellow in acid). Fill the second gas bottle halfway with water.
This is for dousing the burning sulphur.
3. Light the Bunsen burner and place some sulphur into the deflagrating spoon (half a spoonful).
4. Put the spoon into the flame at a 45 degree angle and wait for the sulphur to melt and burn with a beautiful
violet flame.
5. At this point, place the burning sulphur into the gas bottle above the water and cover it as much as possible
with the glass plate (a petri dish can be used if a glass plate is not available). After a moment, you should be
able to see a white gas start to billow in the gas bottle.
6. Once this has occurred, remove the deflagrating spoon (and quickly recap the gas bottle with the glass plate)
and douse it in second water bottle and ask your student helper to move it quickly to the fume hood.
7. During this time, explain about how sulphur burns in factories and reacts with the oxygen in the air to produce
sulphur dioxide which comes out of the smoke stacks. This gas then dissolves into water in the clouds and
comes down as acid rain, which creates health problems for fish and other aquatic organisms. It also creates
damage to buildings, forests and other possible health effects for humans1.
8. Looking at the smoke/water combination in the gas bottle, you may see the smoke dissolving in the water and
turning it yellow. Work quickly at this point! While you are talking about what happens in the clouds, hold the
glass plate firmly on top of the glass bottle and shake the contents of the bottle. The solution changes quickly
from blue to yellow (like acid rain)!
If you’d like to see a video on a very similar demonstration, watch this one: http://tinyurl.com/burningsulphurvideo.
It may help you be able to follow my written directions a bit more easily.
Reference on the hazards of sulphur dioxide:
Hazardous Chemicals: A Manual for Schools and Colleges, by Oliver and Boyd of the Scottish Schools Science Equipment
Research Centre. 1980.
1
http://www.epa.gov/acidrain/effects/health.html
Acid Rain Demonstration – Page 2
Volume 44 • 4 April 2013