1.5.3 Heating and Cooling Curves

• What is the dependent variable shown on the y-axis of the graph?

  Temperature (°C)
• During a plateau, energy is used to increase the temperature of the substance.

  False
• What does a plateau on a heating curve indicate?

  A state change
• What are the key differences between the heating and cooling curves for water shown in the image?

  • The heating curve shows the temperature increasing over time, while the cooling curve shows the temperature decreasing over time
  • The plateaus occur at different points in the heating vs. cooling curves due to the phase changes happening in opposite directions
  • The slopes of the curves differ between heating and cooling due to the energy transfer mechanisms involved
• Match the state of matter with its description:

  Solid ↔️ Fixed shape and volume

  Liquid ↔️ Fixed volume but no fixed shape

  Gas ↔️ No fixed shape or volume
• How does the heating curve for water differ between the solid, liquid, and vapor phases?

  The slope changes at the freezing and boiling points, indicating phase changes
• Arrange the components of a heating/cooling curve in order of their appearance on the graph:

  1️⃣ Temperature

  2️⃣ Time

  3️⃣ Slopes

  4️⃣ Plateaus
• What are the key features of the heating curve for water shown in the image?

  • Gradual increase in temperature from A to B (solid to liquid)
  • Plateau at B to C (melting/fusion)
  • Rapid increase in temperature from C to D (liquid to gas)
  • Plateau at D to E (boiling/vaporization)
  • Rapid increase in temperature from E to F (superheated gas)
• Order the state changes of water as temperature increases on a heating curve.

  1️⃣ Solid (ice)

  2️⃣ Melting (plateau at 0°C)

  3️⃣ Liquid water

  4️⃣ Boiling (plateau at 100°C)

  5️⃣ Steam
• What is the 1.5-degree-limit shown in the graph?

  The 1.5-degree-limit is a horizontal line on the graph indicating the temperature anomaly limit of 1.5 degrees Celsius.
• Why is the 1.5-degree-limit shown in the graph?

  The 1.5-degree-limit represents a target temperature anomaly threshold that should not be exceeded
• If the temperature anomaly trend continues as shown, in what year will it reach 1.5 degrees Celsius?

  Around 2030
• What does the plateau region (CD) in the heating curve represent?

  The temperature remains constant during the phase change from liquid to gas
• What is the temperature anomaly value in the year 1970?

  0.1 degrees Celsius
• What is the title of the image?

  Explaining the Plateaus in Heating and Cooling Curves
• What is the independent variable shown on the x-axis of the graph?

  Time (min)
• Steps in analyzing a heating curve

  1️⃣ Identify plateaus (PE changes)

  2️⃣ Identify slopes (KE changes)

  3️⃣ Determine ΔH°fus

  4️⃣ Determine ΔH°vap
• What is the boiling point of water?

  100 °C
• What does a heating/cooling curve show?

  Temperature changes over time
• How does the graph show that the entropy (ΔS) increases during the phase transitions?

  The horizontal lines at the freezing and boiling points indicate that the entropy increases as the substance changes phase
• What is the temperature at which the liquid and vapor phases of water are in equilibrium?

  100 °C
• What is the expected boiling point of the substance shown in the diagram?

  The expected boiling point is marked on the diagram
• At what temperature does water freeze, as shown on a heating curve?

  0°C
• What is the process of a substance transitioning from a liquid to a gas called?

  Vaporization
• What does the trend line in the graph represent?

  The trend line represents the overall long-term trend in temperature anomaly over the years shown in the graph.
• What is the difference between the freezing point and boiling point of water?

  The freezing point is 0 °C and the boiling point is 100 °C, a difference of 100 °C.
• What are the key features of the heating curve for water?

  • Flat regions at freezing (0 °C) and boiling (100 °C) points indicate phase changes
  • Steep slope for solid and liquid phases
  • Vertical jump in temperature at boiling point, indicating vaporization
• Temperature changes during state transitions in a heating curve.

  False
• What does a plateau on a heating/cooling curve indicate?

  Phase transition
• Match the phase transition with its corresponding temperature change:

  Melting ↔️ Solid to liquid

  Freezing ↔️ Liquid to solid
• At what temperature does water freeze?

  0°C
• What is the freezing point of water?

  0 °C
• What is the freezing point of the substance shown in the image?

  -40°C
• What does the slope of a line on a heating/cooling curve indicate?

  Rate of temperature change
• What formula is used for temperature change in heating curve problems?

  $Q =$$mcΔT$
• What is the melting point of the substance in the example curve?

  0°C
• What is the temperature anomaly value in the year 2030 based on the trend line?

  According to the trend line, the temperature anomaly value in 2030 is approximately 1.4 degrees Celsius.
• How do the plateaus in the heating and cooling curves differ in terms of their physical significance?

  • The plateau in the heating curve represents the energy required for a phase change (e.g. melting, boiling)
  • The plateau in the cooling curve represents the energy released during a phase change (e.g. condensation, freezing)
• How does the temperature anomaly trend compare to the 1.5-degree-limit over the time period shown?

  The temperature anomaly trend line rises above the 1.5-degree-limit in the later years, indicating the trend is exceeding the 1.5 degree Celsius limit.
• What are the three phases of water and their temperature ranges?

  • Solid (ice): below 0 °C
  • Liquid: 0 °C to 100 °C
  • Vapor (gas): above 100 °C