wednesday, december 2, 2015

Given that this is the third day of our new unit, we did our first experiment.  This one involved the relationship between friction and heat.  I will explain it below the warm-up.

Today's experiment involved graphing and the relationship between heat and friction.  I first went over graphing and how graphs are used to visually display data in an easy to use format.  We discussed the three main types and their purposes (bar graph=comparing and contrasting the same type of data; circle/pie = comparing parts to a whole such as fractions and percentile; and, line = changes over time).  While this experiment would best use a line graph, we did a bar graph instead.

I used a non-contact IR thermometer and took a temperature reading of a random student's desk in Celsius.  Students recorded the data on a sheet of graph paper.  I then took the temperature of the desk.  The next step was to have the student place his/her hand palm down on the desk and hold it for 60 seconds.  Afterwards, the palm's temperature was taken again.

While we waited for the minute to elapse, I asked the rest of the class to make a prediction about the temperature of the student's hand.  Would the temperature be higher, lower, or will there be no change?  

After taking the temperature, we noticed that the temperature of the student's palm was lower.  Why?  Because, according to the Second Law of Thermodynamics, heat always flows from warmer to cooler objects.  Since the student's hand is warmer than the desk surface, the heat transferred from the hand to the desk.  The exact spot where the hand was would be warmer.

The last activity in the experiment was to have that same student rub the hands together vigorously from 1-2 minutes.  After measuring the temperature, in almost every case the student's palm temperature rose within a few tenths of a degree from the original temperature.  Students graphed the data and then wrote a one paragraph reflection on it.