Video Transcript
Amelia wraps three beakers in
different materials. She then fills the beakers with
water at 100 degrees Celsius. She measures the temperature of the
water in each beaker 30 minutes later. Her results are shown in the
table. What material was the best
insulator? What material was the worst
insulator?
Okay, so what we have here is an
experiment involving three beakers of water. So let’s say that here are our
beakers. Now we’re told that they’re wrapped
in different materials. One of the beakers is wrapped in
felt, another is wrapped in cardboard, and the third beaker in aluminum foil. Following this, all the beakers are
filled with water at 100 degrees Celsius, that’s boiling hot. Then, 30 minutes later, the
temperature of the water in each of the three beakers is measured. That measure temperature is
recorded in the bottom row of this table of data. Based on all this, we want to know
which of these three materials was the best insulator and which one was the
worst.
To figure this out, we want to know
what an insulator is in the first place. An insulator is a material that
resists the transfer of heat. We’re all familiar with
insulators. For example, each one of us has
probably used an oven mitt, which is an insulating material in order to handle hot
dishes on the stove. So of these three materials — felt,
cardboard, and aluminum foil — the best insulator will be the one that resists the
transfer of heat out of the water the most. The water in the beaker with the
best insulator will be the water that decreases in temperature the least; that is,
it will retain the most of its heat energy. That means that the highest water
temperature will indicate the best insulated beaker.
Looking at our table, we see that
in the bottom row 38 degrees is the highest temperature of the water after 30
minutes. That tells us that the beaker
wrapped in this material cardboard is best insulated. So we’ve write that down as our
answer for the best insulator. It’s cardboard. And then, we move on to consider
what material was the worst insulator. The worst insulator will do the
opposite of a good insulator. It will let lots of the heat of the
water disperse. The result of that heat dissipation
will be that the water temperature will be lowest.
Looking again at the bottom row of
our data table, we see that the lowest measured water temperature is 25 degrees
Celsius. That corresponds to the beaker
wrapped in aluminum foil. Because this water has cooled the
most over the half-hour interval, 75 degrees Celsius, that means it’s insulated the
least. Or in other words, it’s surrounded
by the worst insulator. And that worst insulator is
aluminum foil based on the fact that the water in the beaker wrapped in aluminum
foil cooled down the most.
