Heating and Cooling Curves

The heating curve below represents a sample of a substance starting as a solid below its melting point and being heated over a period of time. Which statement describes the energy of the particles in this sample during interval DE?

• Both potential energy and average kinetic energy increase.

• Both potential energy and average kinetic energy decrease.

• Potential energy increases and average kinetic energy remains the same.

• Potential energy remains the same and average kinetic energy increases.

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

Heat is added to a sample of liquid water, starting at 80.°C, until the entire sample is a gas at 120.°C. This process, occurring at standard pressure, is represented by the balanced equation below.
H₂O(l) + heat → H₂O(g)

Which diagram correctly represents the heating curve for this physical change?

• 
• 
• 
• 

Tags

NGSS.HS-PS1-4

Based on the graph and information shown in Figure 2, what phase change is occurring between minutes 2-6?

• fusion

• solidification

• vaporization

• condensation

Tags

NGSS.MS-PS1-4

Fill in the blank: The graph in Figure 2 shows that the compound is in the ______ phase at 15°C.

• Solid

• Liquid

• Gas

Tags

NGSS.MS-PS1-4

In the heating curve shown, heat is applied to a solid substance at a constant rate. What accounts for the fact that segment CD is longer than segment AB?

• 1. Boiling occurs at a higher temperature than melting.

• 1. The heat of vaporization is greater than the heat of fusion.

• 1. The average kinetic energy increases at a greater rate during boiling than during melting.

• 1. Potential energy is being released during boiling.

A student observing the behavior of paradichlorobenzene first heats 10 grams of the substance in a hot water bath until it is completely liquified. The data in the table shown are recorded as paradichloro-benzene cools. What is the freezing point of paradichlorobenzene?

• 65°C

• 58°C

• 53°C

• 42°C

Tags

NGSS.HS-PS3-4

The graph represents the heating curve of a substance that starts as a solid below its freezing point. What is the melting point of this substance?

• 30°C

• 55°C

• 90°C

• 120°C

Tags

NGSS.HS-PS3-2

How much time passed while the substance went through the phase change of condensation?

• 2 minutes

• 3 minutes

• 5 minutes

• 4 minutes

Tags

NGSS.MS-PS1-4

How much time passed between the first appearance of the liquid phase of the substance and the presence of the substance completely in its solid phase?

• 5 minutes

• 2 minutes

• 7 minutes

• 4 minutes

Tags

NGSS.HS-PS3-4

During which time interval does the substance exist as both a liquid and a solid?

• min 2 to min 4

• min 4 to min 5

• min 5 to min 7

• min 7 to min 9

Tags

NGSS.MS-PS1-4