hey it's professor Dave, let's talk about calorimetry
different substances absorb heat at different rates due to various structural factors. the heat capacity of
a substance is the amount of energy required to raise the temperature of
that sample by one degree Celsius. a variation of this that is more useful
for calculations is the specific heat of a substance, which is the energy required
to raise one gram of a substance by one degree Celsius. heat, temperature, and heat
capacity are all related by the following equations. the amount of heat
exchanged in a reaction is equal to the heat capacity of the substance times the
change in temperature for that substance, or more practically the heat exchange is
equal to the specific heat of the substance times the grams of the
substance present time the change in temperature. we can use this information
to learn about heat transfer using a process called calorimetry. for those of
you in an introductory chemistry course you'll probably do some variation of a
coffee cup calorimeter experiment. let's look at how those work. a coffee cup is a
pretty good insulator, that's why we use it for coffee, so that the heat doesn't
escape so quickly and the coffee stays hot for longer. this makes it possible to
take pretty reasonable data about the temperature change in a cup of water
when we add a hot piece of metal. we can measure the temperature change in the
water and use that information to calculate the specific heat of the metal.
so let's say you heat up a metal by placing it in boiling water at a known
temperature until it is just as hot as the water. then with tongs you place it
in a coffee cup containing a known volume of room temperature water with a
thermometer. the water in the cup will heat up slightly as the heat from the
metal flows into the water and we can record the resulting temperature
change. from there we just do some math. we use the specific heat equation
and plug in the data for the water. the temperature change is what you recorded
the mass of water in grams is equal to the number of milliliters of water, and
the specific heat of water is a known value. this allows us to calculate the
heat absorbed by the water. well, the heat absorbed by the water was the heat
released by the metal. so we can take that same quantity of heat and plug it
into a new equation for the metal. that value goes there, we weighed the metal
beforehand, and this time the temperature change of the metal is from the boiling
water to the final temperature in the coffee cup. so you can solve for the
specific heat of the metal. this is useful for identifying unknown metals if
you are given a few different specific heats and asked to decipher which metal
you are given. let's check comprehension
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