(thermodynamics)

for each systems below, calculate the value for ∆e. show equation and work!

g) a system cools down while expanding. (sign only with explanation)

h) a system heats up a little while expanding a lot. (sign only with explanation)

i) an endothermic reaction does not expand. (sign only with explanation)

Answers:

G. -; H. -; I. +

Step-by-step explanation:

ΔE = q + w

Anything going into the system is positive (+), and anything leaving the system is negative (-).

G. Cooling with expansion

q: Heat is leaving; q is -

w: The system is doing work on the surroundings. Energy is leaving the system. w is -.

ΔE is -.

H. Heating a little, expanding a lot

q: Heat is entering; q is +.

w: The system is doing work on the surroundings. Energy is leaving the system. w is -.

However, the expansion work is the major factor.

ΔE ≈ w. ΔE is -.

I. Endothermic, no expansion

q: Heat is entering; q is +.

w: No expansion. w = 0.

ΔE = q. ΔE is +.