# THERMODYNAMICS REVIEW KEYx

Mechanics

Oct 27, 2013 (4 years and 8 months ago)

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THERMODYNAMICS REVIEW

Vocabulary

Isothermal

E

temperature

A

C

isovolumatic

G

entropy

D

heat

F

internal energy

B

1
st

Law of Thermodynamics

H

2
nd

Law of Thermodynamics

I

Label the following as isothermal (T), Adiabatic (A) or isovolumetric

(V)

__
A
___
generally happens very quickly

__
A
___no Q in or out of gas

__
A
___
Δ
U =
-

W

__
T
___Q = W

__
V
___No work is done on or by the gas

__
V
___W = 0

__
V
___
Δ
V = 0

__
T
___ΔU

= 0

__
V
___
Δ
U = Q

__
A
___Any change in temperature is due to

work being done on or by the gas.

How does a heat engine work?

Heat added to the engine causes the engine to do work as it transfers to a cooler reservoir.

What happens to

the Pressure, Work done, Temperature, Volume of a gas when it is compressed

AND when it expands.

Compression: (increase P, T,
Δ
U) decrease in V
-
Work done on the gas

Expansion: (decrease P, T, ΔU) increase in V + Work done by the gas

Stu
dy all information in the thermodynamics note packet; Review your thermodynamics quiz

Study all information taken in your nuclear notes; Decay worksheet

A Relates to internal energy of an object.

B Internal kinetic energy of atoms in a material.

C No heat is transferred because the gas

expand or compresses quickly.

D A measure of disorder of something.

E No change in temperature because any change in

heat is accompanied by an equal amount of work.

F Internal energy t
ransferred between objects

G No change in volume, so no work is done. Therefore

any change in internal energy is due to

heat.

I Energy tends towards disorder

H Conservation of Energy

Practice
Problems

W = P•ΔV

V = A

d

ΔU = Q

W

W = Q
h

-

Q
c

=

=

1.
Gas in a container is at a pressure of 1.6 x 10
5

Pa and a volume of 4 m
3
. What is the work

done by the gas if it expands at constant pressure to twice its initial volume?

6.4 x 10
5

J

2
. Heat is added to a system, and the system does 26 J of work. If the internal energy

increases by 7J, how much heat was added to the system?

33 J

3
. The internal energy of the gas in a gasoline engine’s cylinder d
ecreases by 195 J. If 52 J

of work is done by the gas, how much energy is transferred as heat? Is this energy added

to or removed from the gas?

-
143 J

4
. If a steam engine takes in 22540 kJ from the boiler and gives up 19150 kJ
in exhaust

during one cycle, what is the engine’s efficiency?

0.15

5
. If the energy removed from an engine as heat during one cycle is 600 J, how much energy

must

be added to the engine during one cycle in order for it to operate at 31 percent

efficiency?

869.6 J

6.
A 208 g sample of sodium
-
24 decays to 13.0 g of sodium
-
24 within 60.0 hours.

What is the half
-