Temperature, heat, and phases
Physical science
Period:
Name:
Date:
AVERAGE kinetic
energy of the atoms and molecules in a substance.
How does the internal energy of 0°C water compare to 0°C ice? How do you know? Because
melting is an endothermic process, the ice had to take in
energy to become a liquid (partially break bonds of
attraction) and thus 0°C water has more internal energy
than 0°C ice
1. What is temperature related to (don’t say how hot something is):
2.
3. Which has the greater the average kinetic energy of the molecules, 0°C liquid water, or 0°C ice? How do you
Since temperature is related to the average kinetic
energy of the particles, and they have the same
temperature, they must have the same average kinetic
energy.
know?
4. Which has the greater the average potential energy of the molecules, 0°C liquid water, or 0°C ice? How do
Since water has more internal energy, but the
kinetic energy is the same between the particles, the
potential energy must be greater.
Why can water boil at a lower temperature when the atmospheric pressure is lower? Boiling
occurs when the vapor pressure in a fluid matches the
atmospheric pressure outside the fluid, if the atmospheric
pressure is reduced, the vapor pressure can be lower,
meaning the fluid will start boiling at a lower temperature
you know?
5.
Below is the heating curve for ethanol, use this to answer questions 6-10
Heating curve for Ethanol
200
Temperature (degrees C)
150
vaporization
100
gas
50
0
-50 0
-100
-150
-200
-250
200
liquid
400
600
800
1000
1200
1400
1600
melting
solid
Heat absorbed by 1 g of Ethanol (J)
6. List the following at the appropriate places on the graph: solid, liquid, gas, melting, vaporization
-105 to -125 (-114.3°C)
What is the approximate boiling point of ethanol?
65 to 85 (78.4°C)
What state of matter is the ethanol in at: -150°C
solid
-100°C
liquid
0°C
liquid 50°C liquid 100°C gas
7. What is the approximate melting point of ethanol?
8.
9.
10. Which takes more energy, converting 1 g of ethanol from solid to liquid, or from liquid to gas? Why is that?
It takes more energy to change 1 g of ethanol from a
liquid to a gas than it does to change it from a solid to a
liquid, because going from a solid to a liquid, the molecules
are still in contact, so the attractive forces are still present,
whereas in going from a liquid to a gas, the attractive forces
of molecules have to be completely overcome, requiring
much more energy.
The following is a temperature vs. time graph for a substance that was a solid, was heated, and then the heat was
removed.
Temperature (degrees C)
Temperature vs. Time
55
50
45
40
35
30
0
100
200
300 400
Time (s)
500
600
If possible write the period(s) of time (e.g. 175 – 225s and 350 – 600s) where each of the following occur, if it doesn’t
occur on the graph write “NA” for not applicable.
0 – 50s and 450-600s
b. Substance is a liquid: 150s -300s (150s to 200s and 200s-300s)
c. Substance is a gas:
N/A
d. Substance is melting:
50s – 150s
e. Substance is vaporizing:
N/A
f. Substance is condensing:
N/A
g. Substance is freezing:
300s – 450s
11. At what time was the burner removed?
200s What state of matter is the substance in at that
point? Liquid
a. Substance is a solid:
12. If possible list the following temperatures, if it can’t be determined, write “can’t determine”
a. Melting point
b. Boiling point
c. Condensation point:
d. Freezing point:
43°C
can’t determine
can’t determine
43°C