Exploring Thermal Phenomena During Phase Change

One demo was set up for the class to observe thermal phenomena during phase change. Emily put ice into a rice cooker, placed a digital thermometer in the ice, and connected the thermometer to the Logger Lite program in order to graph the changes that are occurring.

The graph recorded the phase changes occurring as ice turned into melted ice (water), and eventually turned into boiling water.

Once the graph was complete, we discussed the:

• Level Lines: Heat going into melting, or boiling process
  
• Slanted Lines: Heat going into increasing temperature
  
• Latent Heat: Heat required to melt ice, or evaporate liquid water
  

While we waited for the ice to melt with our demo, small groups worked on the following problem:
A student just learned about thermal phenomena in school. That night, as part of her homework, she teaches the phenomena to her parents. Using thermometers, and cups of hot and cold water, the student decides to create her own experiment. First, she takes the temperature of the cold water, which reads 15 degrees Celsius. Next, she determines that the hot water is 45 degrees Celsius. When both types of water are combined, the temperature is 25 degrees Celsius. She remembers that there were 80 milliliters of cold water but can’t remember how much hot water she used. Determine the amount of hot water the student used in her experiment: Represent this scenario with a graph. Then represent this scenario with an algebraic equation, justify your equation by stating the physics involved, solve algebraically for the amount of hot water, only then substitute numbers to calculate the answer.

The students solved for the mass of the hot water very quickly, and seemed to understand the equation (Mh x Ch x Change in Th = Mc x Cc x Change in Tc) very quickly once they were given numbers to plug into the variables. In fact, they finished so quickly that we asked them to come up with their own numbers to plug into the equation.