Endothermic & Exothermic Reactions
MS-PS1-6.
Undertake a design project to construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes.* [Clarification Statement: Emphasis is on the design, controlling the transfer of energy to the environment, and modification of a device using factors such as type and concentration of a substance. Examples of designs could involve chemical reactions such as dissolving ammonium chloride or calcium chloride.] [Assessment Boundary: Assessment is limited to the criteria of amount, time, and temperature of substance in testing the device.]
Calculating the energy of reaction
Endothermic and exothermic reactions - Temperature vs. Concentration
Note: see keyboard shortcuts for Ssubscripts and Ssuperscripts.
Measure 20 mL of water with a graduated cylinder and pour it into the sampler cup provided.
Stir the water with the thermometer, monitoring the temperature until it is stable. Record this temperature (±0.1° C) as the initial temperature.
Measure 2 g of the chemical salt and stir.
Ammonium chloride: NH4Cl(s) → [NH4]+(aq) + [Cl]-(aq)
Calcium chloride: CaCl2 + H2O → Ca+ (aq) +2Cl-(aq)
Continue to stir and monitor the temperature every 10 seconds for 1 minute. Record the highest or lowest temperature obtained (±0.1° C) as the final temperature.
Clean the thermometer and repeat the procedure using 4g in a new cup
Enter data for Temperature vs.concentration of solute
Create plots of class averages for the following:
Temperature vs. Concentration NH4Cl
Temperature vs. Concentration of CaCl2
Observe and interpret the graphs
Endothermic and exothermic reactions - Temperature vs. Time
Repeat steps 1 to 6 g of chemical salt, recording the data in the table below, as well as the extreme temperatures in the tables in the previous section
Determine the change in temperature. ΔT = Tf − Ti
Enter data here for temperature vs. time
Observe and interpret the graphs
Design a hand-warmer or cold-pack
ETS1.B: Developing Possible SolutionsA solution needs to be tested, and then modified on the basis of the test results, in order to improve it.
Models of all kinds are important for testing solutions.
ETS1.C: Optimizing the Design Solution
The iterative process of testing the most promising solutions and modifying what is proposed on the basis of the test results leads to greater refinement and ultimately to an optimal solution.
A variety of endothermic and 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.
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 toindicate 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)
(11) NH4Cl(s) ----> [NH4]+(aq) + [Cl]-(aq) - Endothermic
Citric Acid, Sodium Bicarbonate, Red Cabbage Juice, Calcium chloride
