Expert: Dr. Henry Boyter, Jr. - 6/21/2005

Question
Would you be able to give me an example of how energy gets transferred during a chemical change?
Thank you very much for your time.
It is well-appreciated.
(my New York State chemistry regent is tommorrow.)
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Followup To
Question -
Hi Dr. Henry Boyter, Jr.,
I have one more question that I'm hoping you could help me with.
Which transfer of energy occurs when ice cubes
are placed in water that has a temperature of
45°C?
(1) Chemical energy is transferred from the ice
to the water.
(2) Chemical energy is transferred from the
water to the ice.
(3) Thermal energy is transferred from the ice
to the water.
(4) Thermal energy is transferred from the
water to the ice.
(answer is 4)
Why isn't the answer,chemical energy?Water doesn't have any thermal energy,it's all in the bonds(polar).so why isn't choice 2 the correct answer?
Answer -
Everything has thermal energy, even near absolute zero.  If water had no thermal energy, it wouldn't melt ice.  Chemical energy is only present when a chemical reaction occurs.  The melting of water is not a chemical reaction, but just a phase change.

Answer
base + acid = water + energy

This is true for almost any acid and base


cellulose/petroleum + O2  = water + carbon dioxide + energy

Any for of wood and petroleum falls into this category.  If not, it would get very cold in the winter.  Whether you transfer the energy to the air, water, or your toes it is the same process.