tuesday, october 6, 2015

Today was different on this eve of our first early release day.  As I had mentioned yesterday, our focus was on the heat conductivity of two different metals:  steel and aluminum.  What was different was that I demonstrated the experiment for the entire 4th grade.  I would do the demonstration for my class and then at the appointed time, Ms. Apoldo brought each class to my room so that everyone can observe and write down the data.  I will discuss it more below.

Yesterday, each parent of a 4th grade student received an email a form for their child to fill out which was simply their prediction of steel or aluminum conducting heat better, or both at the same rate.  My best estimation is that about 44% responded so that is the data I went with.  I know that more tried to submit but their responses did not go through and to that I am not certain. 

Below is a graph of the responses:

How I did the experiment is that I had a lab ring stand with one 3' steel rod attached to a clamp and one 3' aluminum rod attached the same way.  

The first step was to take temperature readings of each bar and record it.  This is the starting, or room temperature.  This will give us a baseline of something to compare to once the blowtorch is fired up and the rods are heated.  

The second step was to choose two student assistants. One to record the data on the board using the following form and the other to use my iPad to take the pictures that are posted below.  All students received a copy and were to glue it in their notebooks.  They recorded the baseline temperatures in their own form.

Step three:  fire up the blowtorch and hold it to one end of the bottom rod for 1-2 minutes or when the end glows a nice fiery orange color.  It need not be exactly 1 or 2 minutes as long as the times for both rods are consistent.  

Step four:  Use the clamping thermocouple to take temperature readings at 10 cm intervals while the student assistant records the numbers on the board.  I used Celsius for the temperature since that is what the rest of the world uses.  The rest of the class records the data in their own charts.  An alternative to the thermocouple is to use an IR non-contact thermometer to take temperature readings.  In fact, I did that for the second and third classes because while the thermocouple is likely more accurate, it takes a lot of time to arrive at the actual temperature.  Using the IR thermometer, all I have to do is aim the laser and within seconds I have the reading. 

Step five:  repeat the process with the other rod, in this case happens to be aluminum.

Step six:  this is the final step and the fifth part of the scientific method.  The question has already been asked.  The students did their research.  Hypotheses were formed and now the experiment was done to test their hypotheses.  Now we analyze the data to see which of the following statements are true:

A)  Steel conducts heat better than aluminum
B)  Aluminum conducts heat better than steel
C)  Both steel and aluminum conduct heat at the same rate

Based on the data, it is clear that the correct statement is aluminum.  Why?  I demonstrated by dropping a different steel rod onto the table from a height of about 2 feet and then a different aluminum rod.  I had the students listen carefully.  The aluminum rod had a higher pitch upon impact and I had another student lift both rods to compare weight.  The aluminum is less dense so energy can travel through it quicker.

An analogy:  imagine there are two rooms and each room has two doors on opposite ends.  Room A has 10 people in it while Room B has 100.  It is clear that it is easier and faster to get through Room A than Room B.

The data is interesting in showing that the temperature spikes in aluminum before dropping off while steel remains fairly constant.  While there is still an increase in temperature at the 10 cm mark in the steel rod, it isn't as drastic as it is with aluminum.

After that, we did the last large task for JA Biztown which is to write a radio ad.  

Tomorrow is the first early-release day so class periods will only be 45 minutes in duration. 
Therefore, tomorrow's focus will be strictly on getting everything finished and final copies written.  I know that Thursday is the deadline for everything to be faxed over to JA Biztown so while there will be a short quiz, the emphasis will not be on science.