[ZOOMING WHOOSH] [BUBBLING]
For experiments 10 and 11, you're essentially using the same tools and techniques.
So, we're going to use one video to encompass the set up for both of those.
And we're doing calorimetry.
So we're doing two different calorimetry experiments.
In experiment 10, we are investigating how to calculate the specific heat of a solution
and metal-- an unknown metal.
The experiment 11 is determining the enthalpy of reactions, which I always think is really
fun and interesting-- to determine whether something is exothermic or endothermic, and
to actually calculate what that value is.
The first step in both of these experiments is calibrating your temperature probe.
So first, we want to have a lower point.
So I have an ice water bath, and I've let it sit for a little while to make sure that
the water and the ice are in thermal equilibrium-- so that water is cold.
If I just add it, the water's not quite cold yet.
So I want to make sure that some of that ice has melted.
And I'm going to enter on the computer 0, for this lower temperature limit.
For my higher temperature limit, I'm going to use my thermometer, and I'm going to have
a hot water bath.
I don't want it boiling, but pretty close to boiling.
And these bubbles are not indicative of boiling water.
These are just some dissolved gases that are effervescing.
You'll be able to tell if it's boiling.
So to set my upper temperature limit, what I'm going to do is put my thermometer and
my temperature probe both in the water.
I don't want to set it down on the bottom of the beaker, because that's really measuring
a much higher temperature, next to that really hot hot plate's surface.
And I don't want to touch the side of the beaker with either my thermometer or my temperature
probe.
I want to hold it somewhere in the solution far enough away that I'm not touching the
sides or the bottom of the beaker.
And I'm going to wait for a couple of minutes, just like with my lower temperature limit.
I'll wait probably 90 seconds to two minutes, and I'm going to make sure the temperature
stops changing before I record it.
Close to boiling is good, if you can get 70 or 80 degrees.
A wide temperature range is going to be really useful.
And once that stops changing, I'll enter in the value on my thermometer as my upper temperature
limit.
Once I've calibrated my instrument for experiment 10, you'll be measuring the heat capacity
of a solution.
And you're also measuring a temperature change, and then calculating the heat capacity of
a metal object.
So I have water in my cup, my very fancy calorimetry tool.
A Styrofoam cup works great, because it's an insulator.
It's really effective.
So any temperature changes are going to be mostly in the solution in the liquid, and
not due to outside interactions.
So I'm going to use my temperature probe.
I want to measure the water temperature before I add anything, because I'm measuring a change
in temperature.
So that's my initial temperature.
I need to leave this piece of metal in my hot water bath for a couple of minutes.
It's going to take a little while to reach thermal equilibrium, to transfer the heat
from the water to this metal object.
So after I've waited several minutes, I'm going to use my tongs.
I'm not going to put my hand in there because it's hot.
I'm going to use my tongs to pick it up, shake off the water, and immediately put it in my
cup.
And then my temperature probe, which is still in there, is going to be recording the change
in temperature.
So after a while, we'll record our final temperature and we'll use that in our heat capacity equation.
So that's experiment 10.
For experiment 11, we need to be careful.
Because not only, I should point out, with our hot plate-- this ceramic white surface
is very hot.
So not only do you not need to touch it, but be careful of all the cables.
Make sure there aren't any cables touching the hot plate surface.
If you're using your temperature probe over here, make sure that you aren't going to melt
the cord.
All right.
So another word of caution about experiment 11-- we are going to be using pretty concentrated
solutions of sodium hydroxide, hydrochloric acid, and sulfuric acid.
And you know that this is a hydroxide-- that's a strong base.
Hydrochloric and sulfuric acid are both strong acids.
So we need to be really careful here.
Make sure you're not wearing your nicest clothes, because the acid is corrosive.
And we used to joke in graduate school that you could point out a synthetic organic chemist
because they had a row of holes in the T-shirt they wore to lab, because of all the nasty
spills on the counter.
And we don't want that to happen to you.
So make sure you're wearing clothing that you don't mind if there is damage to them.
OK, so for this one I'm going to be really careful.
It's really important for this experiment to measure out carefully each of your solutions.
So we're going to be measuring the enthalpy of reaction for a couple of mixtures.
We're going to measure our amount of sodium hydroxide.
We're going to add that to our cup.
Measure the temperature.
I'm going to rinse this out, or use a different graduated cylinder for my acid.
I need to measure the same amount of acid, or I won't have accurate enthalpy of reaction.
So the same amount-- I'm going to make sure I get down on eye level and record that meniscus.
And then after I've clicked start experiment, or begin experiment, I will combine the two
equal volumes of strong base and strong acid.
And over time this will equilibrate, and we'll get a temperature reading.
And we'll use that to calculate the enthalpy of that reaction.
So again be really cautious with the hot plate, and the strong acids and strong bases.
So that's experiments 10 and 11, all about calorimetry.