Science and Engineering Practice 3 calls for students to evaluate the accuracy of various methods for collecting data. In this lesson students work collaboratively with a partner to follow step-by-step instructions which will help them review and refine their ability to measure liquids precisely using a graduated cylinder. Students apply math skills for volume and attending to precision. Measurements are used in a real world activity.
While this lab does focus on step-by-step instructions, it is also an open investigation for students because they do not know for sure what they will see as the end result when all of the steps are completed. This lab also build skill sets needed for future investigations. The Rainbow Measurement Lab, and materials list, are included here in the resources.
I remind students that their eye should be level with the liquid in the cylinder. I also explain that in glass and some plastic cylinders, the water will adhere to the side of the cylinder forming a curve. The curve is called a meniscus. I use my document camera to share drawings of meniscus on pre-printed cylinders and we practice reading the paper cylinders as a group. I will spend a few minutes reviewing how to use the equipment we need for this lab. Meniscus is from the Greeks meaning crescent shaped or diminutive moon.
Create a sheet to practice reading graduated cylinders at Math-Aids. I use this website because it allows me to control the content to meet my needs, while providing me with visual supports for the measurement problems. (It would take me a lot more time to create all of these worksheet tools!)
I share with students that they can use the pipette to add or subtract small amounts of liquid in the graduated cylinder. Note: I always have some students who try to fill the entire amount in the cylinder with the pipette. I remind them that that procedure would be too slow to complete the lab during the class period.
I model for students how to rinse the graduated cylinder before measuring the next liquid. I remind students that they do not want to mix the colors – this would be the same as “contaminating” chemicals.
We use a large container at each set of tables to collect the rinse water and to provide a collection device for the colored water at the end of the lab.
Next, I review the Materials for Rainbow Measurement Lab list with students. I have each lab group check to make sure they have and can identify each of the items. In a quick check, I ask each group to hold-up the pipette or point to the graduated cylinder. This little check of materials also helps to build student vocabulary of science tools.
Students follow the step-by-step instructions to fill each test tube with the correct color and amount of water. I monitor student work to make sure they are using the tools appropriately. It is important to check to be sure they are reading the graduated cylinder correctly and every student is engaged in the process.
When students have food coloring on their hands, the lab table or any other place where it should not be, I use this opportunity to let them know that if we had been using chemicals instead of food coloring this could be a serious problem. I really want them to respect the process and truly work as scientists. A beginning of year lesson like this one can establish expectations for the entire school year. This is better done with a simple, fun lesson rather than something more complicated.
Checking to see if students are using the tools correctly is easy. The end product should have the same amount of liquid in each test tube. I use a quick visual assessment to see who needs additional help as we move forward.
Student Science Journal Entries
We use a science journal in my classroom. Students add a page to their journal for this lab. They draw test tubes and color them with the results seen in the tubes at the end of the lab. If drawing stresses some students, I remind them this is a scientific representation so the most critical part isn't how beautiful their drawing is, but how accurately it shows the work. These students can draw rectangles to represent the test tubes.
Students cutout the table of measurements from the lab instructions and add it to the same page in their journal.
For this lab we focus on documenting through drawing our experience as scientists. Students demonstrate qualitative observations by coloring the test tube liquids as closely as possible to the actual color they see. Students also demonstrate quantitative observations by adding the table with the final measurements in each test tube.
Students also respond to the question, "How did this lab experience make you feel like a scientists?" I ask this question because I want students to think of themselves as scientists in this classroom. We will answer this question again as a group during the whole class reflection questions building towards an understanding of why it is important for scientist to keep accurate records of their work.
Whole Class Reflection Questions
At the end of the lab, I tell students that the volume of liquid in each of the tubes should be the same. Did any group measure the same amount in each test tube at the end of the lab? Then I will ask students to share why they think that not all of the test tubes have the same volume of liquid. Guiding questions for this discussion include:
Why ask these questions? Because I want students to grow as reflective learners as well as scientific thinkers. Science is not a "one and done" experience. We learn something to carry forward with each lab experience.
An introductory, skill practice lesson is an excellent time to model how students might reflect about the lesson and their experimental results. According to John Dewey, student reflection on their experience is where learning takes place.