4. The cooling curve below represents the uniform cooling of a substance, starting at a temperature above its boiling point.
Cooling Curve
5
Temperature (°C)
1
1
1
!
1
i
.
1
1
1
1
0
1
2
3
4
5
6
7
8
9
10
11
Time (min)
During which time interval does the substance exist as both a liquid and a gas?
(1) min 2 to min 4
(2) min 2 to min 6
(3) min 5 to min 7
(4) min 7 to min 9
6