UMUC NSCI 101/103 Lab 5: Chemical Processes

INSTRUCTIONS: • On your own and without assistance, complete this Lab 5 Answer Form and submit it via the Assignments Folder by the date listed on your Course Schedule (under Syllabus). • To conduct your laboratory exercises, use the Laboratory Manual that is available in the classroom. Laboratory exercises on your CD may not be updated. • Save your Lab 5 Answer Form in the following format: LastName_Lab5 (e.g., Smith_Lab5). • Submit your document in a Word (.doc or .docx) or Rich Text Format (.rtf) for best compatibility. Pre-lab Questions 1. Define enthalpy. 2. What is the relationship between the enthalpy of a reaction and its classification as endothermic or exothermic? 3. With instant hot compresses, calcium chloride dissolves in water and the temperature of the mixture increases. Is this an endothermic or exothermic process? Experiment 1: Cold Packs vs. Hand Warmers Time (sec) Temp. (°C) Initial 30 60 90 120 150 180 210 240 270 *300 330 360 390 420 450 Maximum Temp (°C): Time (sec) Temp. (°C) Initial 30 60 90 120 150 180 210 240 270 *300 330 360 390 420 450 Minimum Temp (°C): Graph your data from the tables. You may create the graph on any program, but make sure it can be integrated into this document. Questions 1. Calculate the overall temperature change for the cold and hot pack substance. HINT: This is the difference in the maximum temperature and minimum temperature of each. Cold pack ?T: Hand warmer ?T: 2. Which pack works by an exothermic process? Use experimental data to support your answer. 3. Which pack works by an endothermic process? Use experimental data to support your answer. 4. Which pack had the greatest change in enthalpy? How do you know?