GROUP ACTIVITY•Form a group of 3 students near where you are sitting.

•Work with other members of the group toward an answer. Solitary, individual work is not permitted.

•Convince each other of the correctness of the group’s response. Discuss, argue, and intellectually engage.

•Record your answer with the names of your group members on your group answer sheet.

Group Member Roles

Assign one person to be the scribe. This person is in charge of recording the group’s work on paper to be turned in.

Assign one person to be the spokesperson. This person is in charge of presenting the group’s work to the class.

Assign one person to be the runner. This person is in charge of obtaining and returning materials for the group.

Activity Goal

to investigate the energy involved in a hand warmer

Contents of the Hand Warmer

1. The hand warmer contains a supersaturated solution of sodium acetate. What is a supersaturated solution?

2. The reaction that takes place when the hand warmer is activated produces crystals of NaC2H3O2•3H2O.

What is the name of NaC2H3O2•3H2O?

Observations

3. Observe the hand warmer. Describe how the hand warmer feels (hot, cold, etc.). Record observations.

4. Activate the hand warmer by bending the metal disc. Record observations.

Interpretations

5. Why does the hand warmer feel “hot” to you?Is the reaction that occurs in the hand warmer endothermic or exothermic? Explain.

Energy Diagram

6. Draw an energy diagram for the process of crystallization that occurs in the hand warmer .

The Reaction

7. Given the equation below, determine how many kilojoules of heat energy are released when 146 g of solid NaC2H3O2•3H2O is formed.

Na+ (aq) + C2H3O2 - (aq) + 3H2O (l) --> NaC2H3O2•3H2O (s) ∆H = -

19.7 kJ

Reversible Reaction

12. What is the reverse of crystallization?

13. Is the hand warmer reusable? Explain.