Question

cooling curve
a cooling curve shows how the temperature (y - axis) changes as a substance is cooled down a constant rate over time (x - axis). kinetic energy is (lost / gained) during a cooling curve therefore the temperature goes (up / down).

• the substance starts in the ____________ phase.
• at the first plateau where temperature is (changing / constant), the substance changes from a __________ to a ________. the temperature at this region is also called the __________ point ($t_c$) and is the same temperature as $t_c$ in the substances heating curve.
• when temperature continues to decrease after $t_c$, the substance is completely in the __________ state and continues to (lose / gain) __________.
• at the second plateau the __________ begins to ________. the temperature in this region is called the ________ point ($t_f$). both ________ and __________ states exist.
• when the temperature continues to drop after the plateau, the substance is completely in the ____________ state.

Explanation:

• Kinetic energy is lost during cooling, so temperature goes down.
• Substance starts in gas phase (highest energy state).
• At first plateau (constant temp), gas to liquid (condensation), temp is condensation point (same as vaporization point in heating curve).
• After first plateau (if cooling further), substance is liquid, losing kinetic energy.
• At second plateau (temp constant), liquid begins to freeze (solidify), temp is freezing point (same as melting point), both liquid and solid states exist.
• After second plateau, substance is completely solid.

Answer:

• Kinetic energy is (lost) during a cooling curve therefore the temperature goes (down).
• The substance starts in the (gas) phase.
• At the first plateau where temperature is (constant), the substance changes from a (gas) to a (liquid). The temperature at this region is also called the (condensation) point ($T_{c}$) and is the same temperature as $T_{v}$ in the substance’s heating curve.
• When temperature continues to decrease after $T_{c}$, the substance is completely in the (liquid) state and (continues to (lose) (kinetic energy).
• At the second plateau the (liquid) begins to (freeze (solidify)). The temperature in this region is called the (freezing) point ($T_{f}$). Both (liquid) and (solid) states exist.
• When the temperature continues to drop after the plateau, the substance is completely in the (solid) state.