Energy is conserved ("Skeletal chemistry" 6 of 9)
"Energy governs everything that we can achieve with matter and what matter can do when left to its own devices. It governs the existence of atoms, their electronic structures, their ability to form bonds, the consequences of shape, and the emergence of bulk properties. It also governs the changes that matter can undergo, which immediately turns our attention from structure and towards change, the other half of chemistry."
Build a Battery
Stacking up sandwiches of aluminum foil and pennies is similar to what Alessandro Volta did back when he created the first battery in 1800 -- the "Voltaic Pile." The chemical reaction produces a "voltage" which can drive a circuit (here a speaker), and energy is transferred from the battery to the speaker.
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Penny Battery
Here's a "Voltaic Pile" that uses copper and zinc -- the same metals Volta used. The core of post-1982 pennies is zinc, so sanding them down provides both metals to make a battery that can light an LED. Not only is this a different reaction (hinting at the electrochemical series), the energy-using output is too (light instead of sound).
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Burn a Peanut
Boiling water with a peanut is a fun way to introduce fire. It explains how we can calculate the amount of energy stored in something by measuring the temperature change it causes in water as the burning "combustion reaction" releases the energy.
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Jam Jar Jet
Here's another fuel-burning activity, this one with an almost explosive display of energy release. It demonstrates what happens in jet engines. Check out the video!
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Hot and Cold
This activity uses a nifty insulated wellplate to allow for multiple thermal experiments to be done quickly, and to compare which get warmer or cooler. From the activity: "When chemical reactions occur chemical bonds between atoms are broken and formed. Energy is needed to break old bonds and energy is released when new bonds are formed. If the energy released is greater than the energy needed the temperature of the solution rises. If the energy needed is greater than the energy released the temperature falls."
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"Skeletal chemistry" article
This is one of the nine central ideas that Peter Atkins lays out in his 2005 article, "Skeletal chemistry." Each of the other ideas has its own list in SMILE.