In two separate bags, learners mix water with Epsom salts and detergent. They discover that one mixture becomes cold (dissolving is an endothermic process), and one becomes hot (dissolving is an exothermic process). Learners can then try different powders or different amounts of powders to compare results. This activity also gives ample opportunity for group observations and discussion about what characterizes a chemical reaction. Extensions are listed on page 9 of the activity guide. This activity is part of the 21-activity guide published by OMSI, No Hassle Messy Science with a Wow. All activities in this guide use household materials and all lesson plans include preparation directions, demonstrations, procedure sheets, cross-curricular connections, and scientific explanation of content.