The Irony

Our focus was "heat" on the coldest day of the school year, so far.

C, E and F Blocks reviewed their homework on temperature before defining heat and detailing why it was a different phenomenon than internal energy. We discussed why heat always moves spontaneously down a temperature gradient and described devices that use work to push heat energy up the gradient (air conditioners and refrigerators). The connection between heat, temperature, internal energy and work ended our time, along with an overview of how James Joule pieced together that particular puzzle. Tomorrow, we jump into the concept of specific heat and how to calculate how much heat is gained or lost by an object.

B Block started their period by reviewing yesterday's lab investigations. Mixing warm and cold water produced curved heating/cooling plots that could be explained by Newton's Law of Cooling, which proposes an exponential pattern to heat loss by an object. When the temperature differences are large, the heat transfer is rapid but as the temperatures move closer together, the rate of energy transfer slows until there is zero net transfer of energy when the system reaches thermal equilibrium. We also looked at why our calculated value for the latent heat of fusion for water was higher than expected. The water in our experiment was not pure water (regular tap water) and a portion of the energy transferred by the warm water did not go into the ice. The system was not a closed one, so the surrounding environment accepted some of the warm water's energy and those factors contributed to the inflated values for L_{f, H2O}. Our attention then turned to the definition of temperature and how temperature relates to an object's internal energy. The three basic temperature scales were reviewed, as were the ideas of thermal equilibrium and thermal expansion. Tomorrow, we discuss the phenomenon of heat and how it integrates with out discussions of temperature and internal energy. At the same time, we'll connect it with work.