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.

Endothermic and exothermic reactions - Temperature vs. Time

Design a hand-warmer or cold-pack

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.

(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