We are asked to determine whether each process is exothermic or endothermic and indicate the sign of ΔΗ.
• Exothermic reactions
▪ lose energy, releases heat, temperature of the surroundings increases
▪ involves bond formation (for phase change: gas → liquid → solid)
▪ ΔH is negative
• Endothermic reactions
▪ gain/requires energy, absorbs heat, temperature of the surroundings decreases
▪ involves breaking bonds (for phase change: solid → liquid → gas)
▪ ΔH is positive
Determine whether each process is exothermic or endothermic and indicate the sign of ΔΗ.
a. dry ice evaporating
b. a sparkler burning
c. the reaction that occurs in a chemical cold pack used to ice athletic injuries
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