Combustion or Oxidation
Summary
In this chemistry lab students will burn a magnesium strip to reinforce the concepts of chemical vs. physical changes, reaction types, conservation of mass, formulas and equations, stoichiometry, Lewis structures, and to explore the concept of oxidation/reduction reactions. Students will answer questions during the lab regarding their measurements and observations and also write a lab report to describe their findings.
CollapseLearning Goals
This activity is designed for students to:
1. observe a chemical change.
2. describe the type of reaction taking place.
3. demonstrate the law of conservation of mass.
4. represent the reaction with formulas and a balanced equation.
5. calculate their results mathematically using stoichiometry.
6. express the reaction using Lewis structures.
7. explain the concept of oxidation/reduction with regards to a transfer of electrons.
1. observe a chemical change.
2. describe the type of reaction taking place.
3. demonstrate the law of conservation of mass.
4. represent the reaction with formulas and a balanced equation.
5. calculate their results mathematically using stoichiometry.
6. express the reaction using Lewis structures.
7. explain the concept of oxidation/reduction with regards to a transfer of electrons.
Context for Use
This activity can be tailored for any learning level from elementary to high school depending on which goals your students are capable of mastering. It can also be used multiple times through a course to illustrate the goals as they are covered in class.
Description and Teaching Materials
Materials: crucible and cover, crucible tongs, Bunsen burner, ring stand, iron ring, wire mesh, magnesium strips, emery paper
Procedure:
Burn a piece of magnesium:
a. Take a 10 cm long magnesium strip and clean it with emery paper until it is shiny.
b. Mass the magnesium strip.
c. Mass your crucible and cover, put the magnesium strip into it and weigh it again.
d. Set the covered crucible on a ring-stand and heat until the magnesium completely burns up. Lift the lid occasionally, but try not to let any ashes escape.
e. Re-weigh the covered crucible.
f. Subtract the mass of the crucible and cover from the total mass of the crucible, cover and product. Assignment Worksheet (Microsoft Word 25kB May30 11)
Procedure:
Burn a piece of magnesium:
a. Take a 10 cm long magnesium strip and clean it with emery paper until it is shiny.
b. Mass the magnesium strip.
c. Mass your crucible and cover, put the magnesium strip into it and weigh it again.
d. Set the covered crucible on a ring-stand and heat until the magnesium completely burns up. Lift the lid occasionally, but try not to let any ashes escape.
e. Re-weigh the covered crucible.
f. Subtract the mass of the crucible and cover from the total mass of the crucible, cover and product. Assignment Worksheet (Microsoft Word 25kB May30 11)
Teaching Notes and Tips
Safety: DO NOT stare at burning magnesium! It is bright enough to damage your retina.
Handle crucible and cover with care as they're quite fragile.
Finally, cold porcelain looks very much like hot porcelain, use crucible tongs when handling crucible and cover.
Discussion ideas: This is a great practical example of how chemical formulas can be determined. You might discuss the assumptions that are necessary for solving this problem (Law of Multiple Proportions, for example). You might discuss whether the formula they determined is an empirical or molecular formula. You could also discuss the particulars of the oxidation and reduction involved.
Handle crucible and cover with care as they're quite fragile.
Finally, cold porcelain looks very much like hot porcelain, use crucible tongs when handling crucible and cover.
Discussion ideas: This is a great practical example of how chemical formulas can be determined. You might discuss the assumptions that are necessary for solving this problem (Law of Multiple Proportions, for example). You might discuss whether the formula they determined is an empirical or molecular formula. You could also discuss the particulars of the oxidation and reduction involved.
Assessment
Check student data on the activity questions worksheet and their explanation and diagram of oxidation/reduction reactions. Be sure to see if they correctly identify which reactant is being oxidized and which is being reduced.
Standards
Concepts Covered MN Academic Standards Addressed
reduction/oxidation, IIB1, IIB4, IIC1
conservation of mass,
chemical formulas
reduction/oxidation, IIB1, IIB4, IIC1
conservation of mass,
chemical formulas