Objective: To help students practice revising their procedures to add specificity such that their "experiment" could be "replicated" by another scientist.
- loaf of bread still in packaging
- 1 (or more) butter knife
- jar of peanut butter with lid (or substitute, as necessary to avoid allergies)
- jar of jelly with lid
- cleaning materials and a sense of humor
- (optional) plate
1. I ask the kids to raise their hand if they have ever made a peanut butter (or substitute) sandwich, watched someone make a PBJ, or even think they woudl be able to make one themselves. Except for the wiseguys, all hands go up.
2. I express my confidence in their abilities, then hand out a blank sheet of paper. Singly, or in pairs, students are told to write a procedure for making a peanut butter & jelly sandwich.
3. After 10 - 12 minutes, students are invited to come up and read their procedures, and I will follow their steps VERY LITERALLY. This is the fun part! It always includes a lot of giggles.
Students say, "Put the peanut butter on the bread."
So, I will put the entire jar, lid and all, on top of the loaf of bread (still in the packaging)
Students say: "Put some peanut butter on the knife."
I put a tiny smear of PB on the knife.
4. After the first student reads their proceudure, the next is invited up, and so on.
5. If time permits, allow the students to revise their procedures to add specificity.
6. For the rest of the year, I refer back to this activity when students write things like "take a container" or "add water" or "stir" - we always go back and add "take a 50 ml graduated cylinder" or "add 20 ml of room temperature water" or "stir gently 25 times."
HERE IS THE EXAMPLE I READ THE KIDS AT THE CONCLUSION OF THE ACTIVITY. Invariably, they find ways to argue even this level of specificity. :)
Instructions for making a PBJ sandwich
1. Gather materials needed and set out on counter or other food preparation surface. Materials include: one container of jelly, one container of peanut butter, one loaf of bread, and a spreading utensil (presumably a knife).
2. Open the bread bag, remove two consecutive slices of bread, and lay them flat on the food preparation surface. These slices should have their widest (non-crust) sides flush against with the surface, with one piece appearing as a mirror image of the other. This can be accomplished by taking the two consecutive slices of bread and “opening” them, much like you would a book.
3. Open the two containers, one jelly &one peanut butter, removing the lids and setting them off to the side of the work surface.
4. Take the spreading utensil (referred to from now on as “knife”) and put the knife into the opened end of the jar of peanut butter, scooping the knife in such a way as to pick up an amount of peanut butter roughly equal to the volume of a ping pong ball.
5. Using the knife for transport, place the peanut butter in the middle of one of the exposed (non-crust) sides of one of the slices of bread.
6. Using the knife as a spreader, spread the peanut butter, keeping it on the side of this one piece of bread only, until the peanut butter is of a uniform thickness across the surface of the bread. Peanut butter should leave the surface of the bread at any time, except for small amount that adheres to the knife due to the stickiness of the substance. (This could be wiped off carefully with a finger and licked to conserve peanut goodness.)
7. Next, using the same knife (if mixing is not a concern, otherwise take a moment to wash and dry the aforementioned knife before proceeding), repeat steps 4 – 6 with the jelly. NOTE: a slightly smaller volume of jelly may suffice. Also, the jelly must be applied to the other slice of bread – the side that was originally touching its consecutive piece (now slathered with peanut butter) when they coexisted in the bread packaging.
8. At this point there should be two slices of bread, one with its (non-crust, exposed) surface covered completely with peanut butter, the other with its (non-crust, exposed) surface completely covered in jelly.
9. Now, pick up one slice, turning its condiment-free side from facing the food preparation surface and to facing the ceiling. CAUTION: At no point during this turning should the slice leave your hand!
10. Place the slice from step 9 onto the undisturbed slice, with peanut butter touching jelly orienting the slices so that the shape of the two slices “match” (much like they did in the originally bread container). Avoid overhang. Arrange as necessary.