Problem Analysis:
The provided image is a heating curve worksheet that shows the temperature of a substance as a function of time. The graph has three distinct segments labeled
(1),
(2), and
(3). The task is to analyze each segment in terms of:
1.
Phases or phase changes present.
2.
What is happening to the energy being absorbed from the heat source (in terms of potential or kinetic energy).
3.
Whether a phase change is occurring.
Solution:
####
Segment (1):
-
Initial Temperature: The substance starts at -10°C.
-
Temperature Change: The temperature increases linearly over time.
-
Phase: Solid phase (since the initial temperature is below 0°C, which is the freezing point of water).
#####
Answers for Segment (1):
a)
What phase or phases are present during segment (1)?
- The substance is in the
solid phase.
b)
What is happening to the energy being absorbed from the heat source?
- The energy absorbed is increasing the
kinetic energy of the solid particles, causing the temperature to rise.
c)
What phase change, if any, is taking place?
- No phase change is occurring. The substance remains in the solid phase throughout this segment.
---
####
Segment (2):
-
Temperature: The temperature remains constant at 0°C.
-
Observation: This plateau indicates a phase change.
#####
Answers for Segment (2):
a)
What phase or phases are present during segment (2)?
- Both the
solid phase and the
liquid phase are present simultaneously. This is because the substance is undergoing a phase change from solid to liquid (melting).
b)
What is happening to the energy being absorbed from the heat source?
- The energy absorbed is being used to break the intermolecular bonds in the solid, converting it into a liquid. This energy is stored as
potential energy (specifically, latent heat of fusion).
c)
What phase change, if any, is taking place?
- A phase change is occurring:
melting (solid → liquid).
---
####
Segment (3):
-
Temperature: After the plateau, the temperature begins to increase again.
-
Phase: The substance is now entirely in the liquid phase.
#####
Answers for Segment (3):
a)
What phase or phases are present during segment (3)?
- The substance is in the
liquid phase.
b)
What is happening to the energy being absorbed from the heat source?
- The energy absorbed is increasing the
kinetic energy of the liquid particles, causing the temperature to rise.
c)
What phase change, if any, is taking place?
- No phase change is occurring. The substance remains in the liquid phase throughout this segment.
---
Final Answer:
\[
\boxed{
\begin{array}{l}
\text{Segment (1):} \\
\text{a) Solid phase} \\
\text{b) Kinetic energy increases} \\
\text{c) No phase change} \\
\\
\text{Segment (2):} \\
\text{a) Solid and liquid phases} \\
\text{b) Potential energy (latent heat of fusion)} \\
\text{c) Melting (solid → liquid)} \\
\\
\text{Segment (3):} \\
\text{a) Liquid phase} \\
\text{b) Kinetic energy increases} \\
\text{c) No phase change} \\
\end{array}
}
\]
Parent Tip: Review the logic above to help your child master the concept of heating curves worksheet.
