Chemistry 11 Practice Test 2 Solution Set
1)
Compare the macroscopic and
microscopic properties of sold and liquid phases.
Solids maintain their shape,
liquids take the shape of their container.
Solids and liquids do not change significantly
in volume.
The atoms/molecules in solids are more tightly
bonded than in liquids.
In solids and liquids the particles are close
together (in contact) but in liquids they are able to slide past each other
while in solids the particles (atoms/molecules) remain in the same position
relative to each other.
In liquid phase the particles are moving more
rapidly (they are hotter) than in solid phase for the same substance.
2)
Water ice at 0ºC is melted
to make liquid water at 0ºC by adding 200,000 J of heat energy. How much ice will be melted?
Use the formula q=mL
with L being heat of fusion since this is solid to liquid phase
change. Solve algebraically for m:
m = q/L
with q being 200,000 J and Lf= 3.35 × 105J/kg
so m = 200,000 J/ 3.35 × 105J/kg = 0.597 g
3)
500 g of liquid water at
10ºC releases 17,000 J of heat energy.
What will its final temperature be?
Now use q=mcΔT
and find ΔT algebraically:
ΔT = q/mc
where q is 17,000J, m is 0.500kg (you need to convert to kg given that
c is in kg) and Cliq water = 4186 J/kgCº
So ΔT = 17,000J/(0.500kg
× 4186
J/kgCº) = 8.12Cº
Since initial temp is 10ºC and heat is lost, it
must cool donw by 8.12 Cº to become 1.88ºC
4)
Consider the graph here:
a) What is the melting point for this substance?
200ºC
b) What is the boiling point for this substance?
500ºC
c) For which phase is the specific heat biggest?
Lowest slope has biggest c so
answer is gas phase
d) For which phase is the specific heat smallest?
Highest slope has smallest c
so answer is liquid phase
Data for Water
Lf=
3.35 × 105J/kg
Lv= 2.26 × 106J/kg
Cliq water = 4186 J/kgCº
Cice = 2000 J/kgCº