Sorting Our Way to pH
In this indoor lab activity students will be given a large variety of objects to sort into categories. After practice and discussion, they will then sort food items; first based on their five senses, then by studying their reactions when placed in red cabbage juice. Students document their predictions, observations, the results of their work and their conclusions.
Context for Use
Class size 30
Elementary classroom lab experience
Approximately 2-3 days to complete lesson
Resource Type: Activities:Lab Activity
Grade Level: Intermediate (3-5)
Description and Teaching Materials
1. Any type of collection: shells, button, marbles
2. A variety of food items, such as: vinegar, water, corn starch, lemon juice or lemons, flour, baking soda, pickles,
soda pop, baking chocolate.
3. Juice cooked out of a red cabbage.
4. 5 or so test tubes for each group of students.
5. Strips of litmus paper (optional.)
On day 1 students are given a number of objects from a collection; buttons, shells, etc. They are then instructed to sort the objects into two groups, then to divide each of those groups into two more. Continuing in this manner until they have a group containing only one object. Students should be recording every step of the way, the manner in which they are creating each of their classifications.
The teacher is observing, questioning and noting the conversations that are taking place among the students. A discussion follows regarding the uses of classifying objects in our everyday world. A library, card shop, color crayon box, etc. are practical examples where classifying is extremely helpful. Students may even be assigned to find other places where they see an example of classifying.
On day 2, students are shown the food items from the materials list (vinegar, lemons, flour, etc.) and are given the task of placing these items into categories as they did in the preliminary sorting activity on day 1. The students are again recording their observations and findings in their notebooks and the teacher is questioning and observing students in their groups. Once students have been given ample time to sort the food items, another discussion of their findings should follow. The teacher then introduces the scientific notion that when substances are mixed together, sometimes a reaction takes place. (Possibly day 3) The students will be placing some red cabbage juice in each of their test tubes and then will add a small portion of one food item (somewhat liquefied with distilled water) in each test tube. The students will again record their actions, observations and their conclusions. They will again be instructed to sort the foods based on their reactions with the red cabbage juice. The teacher will again create discussion where the students present their conclusions and the results of their final sorting. At this time the concept of pH can very basically be presented. If the teacher chooses, students can continue on to a more in-depth study of pH.
2. Recognize that clear communication of methods, findings, and critical review is an essential part of doing science.