Endothermic & Exothermic Reactions

Chemical processes or reactions that produce heat, like those occurring in heat packs, are termed exothermic (exo- out; therm- heat). The reactions that take place in your fireplace, the cylinders of your automobile engine, or the furnace in your home are exothermic. Processes or reactions like those in cold packs that remove heat and cool the surrounding environment are termed endothermic (endo- within; therm- heat). The dissolving of salt in the drum of an ice cream maker, or the expansion of freon or other refrigerant gases in an air conditioning unit are endothermic processes.

  • Place the temperature probe in the liquid phase for 20 seconds to get a baseline temperature. Add about 1 gram of solid to test tube and stir with 3 mL of solution with the temperature probe. Report the biggest temperature change observed after one minute. Indicate a drop in temperature (endothermic) with a negative sign.
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  • Perform all of your tests on the same graph. Upload a screen capture of your graph here. Make certain to label the photo with your team names.
  • Examine the class data and complete this lab report collaboratively as directed by your instructor. Use your team colors to indicate which additions you have made.

(1) CaO(s) + H2O(l) -→ Ca(OH)2(s) (Lime + water)

(2) NH4NO3(s) + H2O (l) → NH4+(aq) + NO3-(aq) (ionization of ammonium nitrate, a fertilizer)

(3) HCl(dilute) + NaOH(dilute) → H2O + NaCl (Neutralization)

(4) NaCl + H2O → Na+(aq) + Cl-(aq) (dissolving table salt)

(5) CaCl2 + H2O → Ca+ (aq) +2Cl-(aq) (De-icing roads)

(6) NaHCO3(s) + HCl(aq) →H2O(l) + CO2(g) + NaCl(aq) (Neutralization)

(7) CH3COOH(aq)+NaHCO3(s) →CH3COONa(aq)+H2O(l)+CO2(g) (Baking soda & vinegar)

(8) C12H22O11 + H2O (in 0.5M HCl) → C6H12O6 (glucose) + C6H12O6 (fructose) (Decompsing table sugar)

(9) KCl + H2O → K+(aq) + Cl-(aq) (dissolving potassium chloride)

(10) NaCl + CH3COOH(aq) → Na+(aq) + CH3COO- + HCl (preparing HCl to clean tarnished metals)