Activities for Teaching and Learning about Changes to Matter: Dissolving and Chemical Change

Introduction

Many of the activities involving changes to matter relate to common phenomena, but challenge students to look at them in new ways. In this article we start with activities on dissolving and mixing, highlighting the important distinction, but with both phenomena representing a physical change. We follow with some chemical change activities which also involve ‘mixing’ of substances but in these cases, new materials are formed, with different properties. The formation of a gas in an acid-base reaction is an example of this or burning which involves a reaction between oxygen and a substance to form, for instance, carbon in the case of organic material, and carbon dioxide. Distinguishing between physical and chemical changes is not always easy, particularly if you do not have access to the concept of atoms and molecules. You can get several surprising effects from chemical reactions. In the early and middle school years, only simple reactions are appropriate, such as that between sodium bicarbonate (baking powder) and vinegar (or any mild acid) to produce carbon dioxide. This reaction is the basis for many intriguing activities, with effects that depend on the gas production. Cooking provides some excellent examples of both physical and chemical change and is a useful and popular activity in classrooms. In the ‘kitchen science’ section of this topic you can focus on techniques for observing and understanding the changes that occur in cooking and use some novel recording strategies.

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