I begin this lesson by reviewing what energy is based off of a previous lesson and class discussion. Energy is a difficult concept for some students to really think about since it is such an abstract comment. My students need a constant review of our class working definition that energy is the ability to do work.
For this lesson, students work with their learning partner. Learning partners in my classroom are students that sit next to each other at their tables. I change student learning partners every month to allow for students to have many opportunities to work with different classmates throughout the year.
I give each partner group six different sheets of colored paper. The paper is pre-cut into 3 inch squares. (white, black, green, red, purple, yellow) I also give each partner group six small ice cubes and a small container to hold all supplies. I instruct students that they will work together to predict and explore which color of paper will cause the ice cube to melt the quickest. (Some students will already have an idea that dark paper will melt the ice cube quicker because they have prior experiences with this idea, however, the hands on investigation allows students to carry out an investigation, practice observation skills and draw conclusions from the investigation, all important components of the NGSS.
You can see in this photo a student predicting the order of papers. This student has ordered the paper from the paper that will absorb the most light to the least light.
The inquiry part of this lesson is critically important. Scientific inquiry reflects how scientists come to understand the natural world, and it is at the heart of how students learn. From a very early age, children interact with their environment, ask questions, and seek ways to answer those questions. Understanding science content is significantly enhanced when ideas are anchored to inquiry experiences.
Scientific inquiry is a powerful way of understanding science content. Students learn how to ask questions and use evidence to answer them. In the process of learning the strategies of scientific inquiry, students learn to conduct an investigation and collect evidence from a variety of sources, develop an explanation from the data, and communicate and defend their conclusions.
For the experiment, I lead the students to an open area outside near my classroom. Students bring all supplies with them and then set their paper on the sidewalk, under the sun. Students place an ice cube on each sheet of colored paper. Students record their observations in their science notebooks. As each minute goes by, I call out how long the ice cubes have been on the paper.
As students make observations, I circulate between partner groups and ask guiding questions to propel thinking.
You can see and hear in this video a "check - in" with students about how their experiment is going. In the beginning of the video you can hear a student saying that the white paper seems to be melting the ice cube the fastest, but by the end you hear him say that the white paper and black paper were almost even. This video was within the first minute of the experiment. (One thing to note was that the first paper to get an ice cube was the white one which could account for the quicker melting. It had been on the paper, and the ground, longer than any other ice cube.)
In this video, you can hear students using some correct science vocabulary and see that the red paper is melting the ice cube more quickly than the other colors.
When most groups are finished with observations, I lead a class discussion with the students about light and absorption. Many fourth graders already know or have background knowledge that black colors absorb light, while light colors reflect light. Through the class discussion, I guide students to see that light energy can be converted to heat or thermal energy when certain materials absorb it. Some materials are heated more than others by light that shines on them.
Dark materials absorb more of the visible spectrum of light. The absorbed light energy is converted and is released as heat energy. Since more of the spectrum is absorbed there is more energy that is converted to heat. Light colored materials absorb less and reflect more of the light spectrum (less energy) so less energy is released as heat
Also, in the class discussion, I go over the results of the partner experiments. I check to see if groups arrive at similar results. If groups did not get similar results, I talk with my students about reasons why that could occur.
I give students an opportunity to apply their knowledge to discover how light energy can be transferred into heat energy. I instruct students to lay 6 new pieces of colored paper on the window ledge in the classroom.
(note: in the photo above, not all pieces of paper are receiving the same amount of light, we did fix this prior to the experiment)
Students then leave their papers to absorb light for about 20 minutes. While the papers are sitting in the window absorbing light from the sun, students work in their science notebooks, adding these vocabulary words with definitions:
(students can use science books, prior knowledge, dictionaries, and this website to help define the words.)
When most students appear to be done with defining the words, I lead a brief discussion about each word and together we come up with a definition for our science notebook.
Then, I instruct students to use the back of their hands or cheeks to feel the temperature of the 6 colored pieces of paper. Students use crayons to color the order from coolest to warmest paper in their notebooks.
You can see several students feeling each paper with the back of his/her hand in these photos.
To wrap up this lesson, students reflect on their experiments from today and explain why it was possible for an ice cube to melt, and where the energy came from to melt the ice cube in their science notebooks. I pose these two questions for students to answer:
1. Why is it possible to melt a ice cube with paper and where did the energy come from?
2. In the future if we want to use objects to heat other objects, what colors should we use and why?