Feel the Heat Answer Key

Vocabulary: calorimeter, conductor, controlled experiment, dissolve, endothermic, exothermic,

insulator, solute, solution, solvent, surroundings, system

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

[Note: The purpose of these questions is to activate prior knowledge and get students thinking.Students

are not expected to know the answers to the Prior Knowledge Questions.]

Eduardo hurts his knee during a basketball game. The trainer applies a cold pack, which getscold after

being squeezed. The next day, Eduardo’s friend Beth is going sledding. Beth buys some hand warmers

and puts them into her gloves. All morning, her hands stay toasty warm.

1. How do you think these devices work?

Answers will vary. [Cold packs typically work by dissolving a salt such as ammonium nitrateinto

water. Commercial hot packs work by crystalizing sodium acetate or by oxidizing iron.]

2. Where do you think the “cold” and the heat comes from?

Answers will vary.

Gizmo Warm-up

As you saw with the instant cold pack and the hand warmers, some reactions

absorb energy while others release it. In the Feel the Heat Gizmo, you will

explore these energy changes while making your ownhot and cold packs.

To begin, select the TEST POWDERS tab. Drag a bottle of NaC2H3O2

(sodium acetate) from the shelf. Using the sliders, decide how much water

and powder to add. Note the beginning temperature, and then press Play

( ) to see what happens.

1. Did the temperature go up or down? Up