Suppose you store a 15.5 g piece of aluminum (Cp of Al = 0.902 J/g⁰C) in the refrigerator at 2.3⁰C and then drop it into your coffee. The coffee temperature drops from 95.6⁰C to 45.6⁰C. How many Joules of energy did the aluminum block absorb?

605.4 J

Explanation:

When a certain substance absorbs a certain amount of energy, its temperature increases according to  the equation:

where

Q is the heat absorbed

m is the mass of the substance

C is the specific heat capacity of the substance

is the change in temperature

In this problem, we have:

m = 15.5 g is the mass of the piece of aluminium

C = 0.902 J/g⁰C is the specific heat of the aluminium

is the change in temperature of the aluminium (in fact, at thermal equilibrium, the block of aluminium reaches the same final temperature as the coffee)

Therefore, the energy absorbed is

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).