Lab #8 – Hand Warmers
Objective: Determine the best solid to use for making a hand warmer. You must justify your choice based on the criteria below.
Criteria: Your hand warmer will consist of no more than 10 grams of an ionic solid and must have an inner pouch with exactly 40 mL of distilled water. The amount of heat produced must be considered. The toxicity and cost must also be taken into consideration. The heat produced can be calculated using the standard enthalpies in the back of your textbook. The toxicity and environmental impacts can be found by reading the MSDS (Material Safety Data Sheet) for each compound. Just do a search for MSDS followed by the name of the compound. Pricing information can be found in the Flinn catalog.
Ionic solids: You must choose from the following solids.
CaCl2KOHLiClNaOHNH4NO3NH4SCN
calciumpotassiumlithiumsodiumammoniumammonium
chloridehydroxidechloridehydroxidenitratethiocyanate
Background: When a phase change occurs, such as changing from solid to aqueous, a transfer of heat will also take place. In some phase changes, such as condensation and freezing, the process is always exothermic. In the case of dissolving a solid, it can be either endothermic or exothermic, depending on how much energy is required to break the ionic bonds in the solid.
Procedure: You may test various solids in the lab for their ability to release heat while being dissolved. You may also choose to do calculations to determine the heat of solution and research the safety information prior to experimentation to narrow down the list of possible substances.
Lab report: Your report may be submitted electronically or in your lab notebook. Your report should include a title and an objective. All of your work should be dated accordingly. You should have a Procedure/Raw data section describing your methods and including all of your measurements. The Analysis/Calculations section should include an organized version of your data along with any calculations that were performed and graphs that were constructed. Your final rate law and the value for k should also appear in this section. The Conclusion should be a re-statement of your objective that includes your choice of solid and a justification of that choice.