Boiling & Melting Point HW
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by Angela Peterson
| 6 Questions
Note from the author:
boiling point & melting point HW
What happens to the temperature of a block of ice when you put a Bunsen burner underneath it?
You might think that the temperature goes up smoothly, but that's not what happens. The graph of temperature against time is called a heating curve. Let's look at the heating curve for water.
Melting point is where the solid turns into a liquid like when butter is too close to stove and it melts.
Solidification is when a liquid turns back into a solid like melted butter put into a refridgerator.
Boiling point is where the liquid turns into a gas like leaving a pot on stove to boil water for pasta.
Condensation is when a gas forms back into a liquid like the vapor from your pot forming droplets on the window.

1
1
The graph below represents the heating curve of a substance that starts as a solid below its freezing point.

What is the melting point of this substance?
A . 30 deg C
B . 55 deg C
C . 90 deg C
D . 120 deg C
2
1
Substances with higher boiling points and higher melting points have more attractive forces between their molecules. The more attraction there is between the molecules, the more energy is needed to pull the molecules apart from one another to get the molecule to change phase. In the below chart, which one has the strongest, most attractive forces between the molecules?

A HF
B CH3Cl
C CH3F
D HCl
3
1
What is happening to the average KINETIC (moving) energy of the particles in segment BC of this graph?

A The temperature is going up representing an increase in the moving or kinetic energy of the particles
B The temperature is going down representing a decrease in the moving or kinetic energy of the particles
C The temperature is staying the same representing energy going into the breaking apart of the attractive forces of the molecules and an increase in potential or stored energy of the substance.
4
1
Identify the process that takes place during line segment DE of the heating curve.

A . melting
B . solidification
C . vaporization
D. condensation
5
1
Given the heating curve where substance X starts as a solid below its melting point and is heated uniformly:
Identify where the average kinetic energy is increasing in our graph.
A . segment AB
B . segment BC
C. segment CD
D. segment DE
E. segment EF
6
1
How would the particles appear at point F in this graph?

A . The particles of the substance would be very close together
B . The particles would be far apart enough to move around one another in a circular like motion
C . The particles would be very far apart, filling up the entire container with their rapid movement.