Students study the various energy changes that occur with the formations of solutions for laboratory salts. From this data they will create the best and safest hand warmer. Students will determine the heat of solutions for each solid and analyze the cost and safety information with provided safety data sheet. The activity contains enough materials for 15 groups of students as well as a Teacher’s Guide and Student Study Guide Copymasters. Meets Big Idea 5, Investigation 12, Primary Learning Objective 5.7.