Principles illustrated
-bleaching agents
-oxidation/reduction
-chemical change
-chemical reaction
Detailed Explanation of Discrepant Event
1.By burning the sulfur, sulfur dioxide gas (SO2) is formed.
2.The red coloring in the rose is being reduced and turns white.
3.Therefore, the sulfur dioxide is acting as a bleaching agent as well.
SO2 + red rose pigment---> SO42- + reduced pigment (white)
Going further:
the reduced pigment (white) can be oxidized again by putting the rose in nitrogen dioxide gas. See video below.
reduce pigment (white) + NO2---> NO + oxidized pigment (red)
Prior knowledge & experience:
Root question:
1. What is happening to the color of the rose?
Target response:
Burning sulfur must be bleaching out the color
Common Misconceptions:
1. While the rose wilted from the heat produced from the burning sulfur, it did not die yet its color was removed.
Other possible questions:
1.What part of the rose started to change color first?
2.What type of reaction is taking place?
3.What gas is formed when sulfur burns?
4.What other bleaching agents do you know?
5.What is the function of the watch glass over the beaker?
Procedure
1.Attach the wire to the stem of the rose
2.Let it hang from the side of a beaker
3.Place a small amount of sulfur powder in a crucible
4.Drop a match into the sulfur
5.Immediately cover the beaker with a watch glass and place in a fume hood
6.For best results - keep covered
Safety precautions
1.The sulfur dioxide produced is a very pungent gas and is also poisonous when inhaled in large doses
2.This experiment should only be done in a fume hood or outside
References & Links:
1.Science Inquiry
2.Discrepant Events
3.A collection of demonstrations from the 1999 NSTA
4.Video Source
Adapted from
