Is Humpty Dumpty falling off the wall and cracking on the ground a physical or chemical change?
I love the Far Side Cartoon with Humpty Dumpty as a giant omelet in a diner, and the caption says something like “Humpty Dumpty’s final days”. Would that be a physical or chemical change?
I usually use the Humpty Dumpty analogy when I start talking about Physical and Chemical Changes.
This following activity is one that I used last year for the first time and it worked really well. The kids were so engaged and felt really satisfied when they figured it out. They will be able to use their Foldable as a resource for this activity.
To prepare this lesson, I printed out the activity cards on pages 2 & 3, laminated them, and cut them apart. I placed each set of cards in a zip-top bag, one per group of 2 students.
On their desks, I have the students place the “Physical Change” card to their left and the “Chemical Change” card to their right. Now they have to sort each card into the correct column. You can do one together to demonstrate the procedures. The kids continue to sort the cards until they have all 15 lined up in the correct columns. When they are done, they raise their hand to call me over and see if their cards are in the right place.
I walk over and when they ask if they have it right, I smile and say “Nope”. (Usually there are a few in the wrong spot, no one got it on the first try last year). So now they have to evaluate what they did and figure out what is in the right spot and what is not. I usually give the kids 2 or 3 tries without any hints from me. Then I give hints like “You have 3 in the wrong spot” or “Everything in your physical change column is correct so far.” (There may be 1 or 2 in the chemical change that need to be moved over.) Or “You have to switch one from each column”, but I won’t tell them which ones.
Once they have everything correct, I push/pile up the physical change card together and give them to one lab partner and tell them to write it in their lab journal. I push/pile up the chemical change cards together and give it to the other lab partner to write in his/her lab journal. Then I tell them to switch cards so they have everything written down in both journals. We keep it top secret so their nosy neighbors don’t see their answers! =)
I love seeing the lab partners talk about where each item goes and they get into some great discussions, they try to reason with their lab partner, they compromise, sometimes they argue, etc…
Students will answer analysis questions and write a conclusion.
Answers for Physical Change: cracking eggs, slicing bread, ice melting, glass breaking, boiling water, fresh lemonade, mowing the lawn.