Conservation of Mass.
The purpose of the following six activities is to collect experimental evidence for the conservation of mass, and to identify any problems with experimental design where mass appears to be unconserved. Each group should perform each activity at least twice to maximize the amount of class data we can gather. Report your data on the board in front of the class room. Copy all of the class data into your own notebook, and use it to construct histograms for each activity.
Following are only general descriptions of each activity. You will need to fill your notebook with a detailed description of the procedure you followed.
Activity 1.
Compare the mass of a compacted piece of steel wool, and a fluffed up piece of steel wool.
Activity 2.
Compare the mass of ice before and after it melts.
Activity 3.
Prepare two vials, one with a 0.1M solution of calcium nitrate and the other with a 0.1M solution of sodium carbonate. Compare the mass of these solutions before and after they are mixed. Record your observations throughout, noting any evidence that a chemical change is taking place.
Activity 4.
Compare the mass of steel wool before and after it is lit to flame. Practice safe lab procedure! Use only a very small amount of steel wool, fluffed to fill a maximum volume. Use a 9 volt battery to start the fire. Again, record your observations throughout, noting any evidence that a chemical change is taking place.
Activity 5
Compare the mass of sugar before and after it is dissolved in water. Plan your procedure carefully, to be sure that you are massing the same materials before and after the sugar dissolves. Leaving out the mass of a container, for example, could dramatically alter your results! Again, record your observations. Is this a chemical or physical change?
Activity 6
Compare the mass of alka seltzer, before and after it dissolves. As always, plan your procedure carefully to include the same materials before and after the reaction. Record your observations. Is this a chemical or physical change?