This is a classic Dancing Raisin Activity with a twist! All ages are fascinated with the movement of raisins in soda. But what about other objects? What does it have to do with buoyancy?
Raisins are denser than the liquid in the soda, so initially they sink to the bottom of the glass. The carbonated soft drink releases carbon dioxide bubbles. When these bubbles stick to the rough surface of a raisin, the raisin is lifted because of the increase in buoyancy. When the raisin reaches the surface, the bubbles pop, and the carbon dioxide gas escapes into the air. This causes the raisin to lose buoyancy and sink. This rising and sinking of the raisins continues until most of the carbon dioxide has escaped, and the soda goes flat. Furthermore, with time the raisin gets soggy and becomes too heavy to rise to the surface.
The purpose of these activities is to help students construct explanations based on scientific information and evidence. Constructing explanations helps students understand the interactions of matter as they observe the properties of density and buoyancy. The crosscutting concepts of systems and system models along with cause and effect are woven into the activities to assist students in building science literacy. Students in upper elementary grades and middle school begin to recognize the relationship between explanation and evidence. Background knowledge guides the types of observations made and the interpretations of those observations. In turn, the activities students conduct become experiences that shape and modify their pre-conceptions.
There are three dimensions to the new 2011 Framework for K-!2 Science Education-Scientific practices, Core Disciplinary Ideas, and Crosscutting Concepts. This lesson addresses the Scientific Practice of Constructing Explanations, the Core Disciplinary Idea of Matter, and the Crosscutting Concepts of Systems and System Models, and Cause and effect: Mechanism and Explanation.
The lesson includes teacher directions and background notes, student recording pages, rubrics for scoring, science notes for students, and a multiple choice practice. It is similar to the bundled lesson Matter Interactions: Solids Liquids and Gases yet this lesson's focus is scientific explanations as the other has a focus of teaching process skills.
A full slideshow of the lesson can be viewed at http://scienceandkidsactivities.com/ under the Physical Science tab.