Burning Steel Wool

Description:  This is an excellent phenomenon to discuss chemical reactions and the conservation of mass. Steel wool is burned leading to an increase in mass. When doing this in class show the students the burning steel wool to begin with and have them predict the change in mass. Most students believe the mass will either increase or decrease. This phenomenon can be used at the beginning of a unit on chemical reactions and students can investigate their individual models. (e.g. mass comes from fire, oxygen, carbon, etc.)

Web Resources:  Combustion of Iron Wool - CFNS Experiment 36

High School Chemistry Mass change during a chemical reaction Iron wool/steel wool is placed on an electric balance and ignited using a burning splint. The change in mass can be observed as the iron wool burns. Students should be able to explain why the mass reading on the balance increases at the end of the experiment.

A good experiment for youngsters.Ask first: Does iron burn? 'No' they say. Ask: When things burn do they get heavier or lighter? 'Lighter' they say. Use iron wool, not steel wool and get the finest grade you can get from the ironmongers.

Limiting Reactant

Description:  In this phenomenon both magnesium metal and hydrochloric acid are limiting reactants.  I have used this in a chemistry class, framing it as "The Case of the Mixed Up Masses".  I tell them that I added varying amounts of magnesium metal but I forgot to label the flasks.  If done correctly they should get the curve seen below.  I learned about this on the NSTA Resource page.  

Web Resource:  NSTA Stoichiometry Balloon Race

Professor Jim Holler of the University of Kentucky demonstrates the concept of limiting reactants with magnesium and hydrochloric acid.