Students have been studying the Law of Conservation of Matter and investigated a rusting reaction to reinforce the concept. Students put wet steel wool in a beaker and covered with a balloon to make a closed system. Students found then mass of the beaker.
After the steel wool rusted, they also found the mass - which they found to be the same after reaction. Students were asked to NAME the process - and identified it as observing the Law of Conservation of mass. Students were then asked to EXPLAIN the Law of conservation of Matter using a word bank (after, mass, oxygen, rust, steel wool.)
During the reaction the balloon got sucked into the beaker. Students were asked to GIVE REASONS why the balloon was sucked in, but need to look at the chemical equation: 4Fe + 3O2 --> 2Fe2O3. Students corrected said that oxygen was taken out of the air in the beaker and added to the rust, thereby creating a vacuum.
Students were then asked to GENERATE ALTERNATIVES. I asked students to infer what would happen to the mass if there was a hole in the balloon. As a class we discussed the difference between an open and closed system. Students correctly inferred that a hole would allow oxygen to enter the system from outside the beaker thus making the mass higher than before.
Connect - This lesson connected to what I already know because I understand the importance to looking at the big picture, which often is a process that I hope students make a connection to.
Extend - This lesson offered a good variation from what I typically asked students to do during an investigation that is not conducive to follow the scientific method.
Challenge - I contemplated using this investigation to kick off the unit before students already had a good understanding of the Law of Conservation of Matter from reading about it. I am curious if this lab would have more impact if I followed more of an inquiry model.
