SAMPLE LAB REPORT PREPARED FOR CHEM 1151 Your Name Chem 1151 Section 3 Endothermic and Exothermic Reactions Date of Experiment Your Lab Partner’s Name The purpose of this experiment is study the energy associated with two chemical reactions. By measuring the increase or decrease of the temperature of the reaction solution, it was determined that one chemical reaction absorbed heat (endothermic) and the other released heat (exothermic). A handheld Palm unit and temperature probe were used to measure and record the temperature change of the reaction solution. Other changes associated with the chemical reactions were observed. Each lab report is worth 10 points except experiments carried out on the same day (e.g. Expts 1A +1B are worth 10 altogether; same for Expts 8A+8B and Expts 9A+9B) and experiments carried out over two weeks (e.g. Expt 11 is worth 20 ) 10% of the lab report is assigned to the Pre-Lab Assignment which must be completed before the experiment is started. The Pre-Lab assignment consists of the Pre-Lab Assignment published in the lab manual and preparing your lab notebook with the title, date and purpose of the experiment, and tables for data entry. This assignment should be completed in your lab notebook and you need not submit it in your lab report. When you arrive in lab, your TA will check your lab notebook and record whether the Pre-Lab is done. I. DATA (Present your raw data in prepared tables; each table needs a number, title and units. Any graphs and computer printouts you printed in lab should be included in this section.) Table 1 Final temperature, t2 Initial temperature, t1 Temperature change, Δt II. Initial and Final Temperatures of Reaction Solutions Part I Citric Acid + Baking Soda 13.40 oC Part II HCl + Mg 18.55 oC 21.12 oC -5.15 oC +3.93oC 25.05 oC OBSERVATIONS (note evidence of a chemical reaction (temperature change, evolution of a gas, precipitation, neutralization), physical properties (like color, state of matter) and changes in physical properties. Part I: Bubbles were given off showing that a gas was produced when reactants were mixed. The baking soda disappeared. The reaction container cooled down. Part II: Mg metal dissolved. Bubbles were given off. The reaction container warmed up. III. CALCULATIONS AND RESULTS (This is the section where you show how you treated your raw data. Include one sample of each type of calculation. If you analyzed your raw data on Excel, describe the x and y variables, include the equation you used, attach the spreadsheet and show how you calculated the desired final values. Your final values should have the correct number of significant figures and units.) The change in temperature is Δt = t2 - t1 = 13.40-18.55 = -5.15 oC for Part I. Repeat this calculation for Part II. Two graphs (one for each reaction) should be included in this section. IV. CONCLUSIONS AND POST-LAB QUESTIONS (This is the section where you interpret your data and answer any post-lab questions at the end of the experiment.) The reaction in Part I is endothermic because it absorbed heat from the reaction solution causing the solution to cool down. This reaction has a negative Δt value. The reaction in Part II is exothermic because it released heat to the reaction solution causing the solution to warm up. This reaction has a positive Δt value. A reaction that is taking place may give off a gas, warm up or cool down, dissolve a solid, change color, form a solid. The reaction in Part II occurred faster because it reached its final temperature, t2, faster.