we did a lab on chemical change, where we had to see how a chemical change affcts mass. so we measure the mass of 20ml of copper solution, and 2cm(cubed) of steel wool, and then we mixed them into a flask. soon the steel wool turned rusy, and broke apart. and the duofilm(which is a strtchy rubery lid) popped up as tho gas was produced.

Question

then we had to answer some questions:here is the question i need help with.

sometimes in an experiment there are flaws due to lack of design and materials, therefore causing mistakes. what are 3 sources of errors in the experiment that might cause a change in the outcome of the chemical change, and name 3 ways to fix them.