1.- Different types of light (infrared, microwaves,
photons, X-rays, etc... ) all interact with
molecules in different ways.
bonds between atoms in a molecule as little
springs. In a real molecule at room temperature,
the atoms are always bouncing back and forth on
those springs randomly. When an infrared photon
hits a molecule, the photon is absorbed by the
molecule, and all that energy goes causes the
atoms to vibrate more, like in this gif:
Those vibrations cause the substance to heat up.
Microwaves, on the other hand, heat up
molecules by making them spin around.
2.- In liquid water, all of the atoms are
vibrating around within individual water
molecules, and the water molecules are moving
around and spinning randomly. Each molecule also
has a weak attraction to the other
molecules around it. All of these weak attractions
between all of the different water molecules in a
cup of water keep the water together as a liquid.
Since the movement of all the molecules is random,
some molecules are moving faster than others. Some
are even moving so fast that they can break free
from their attractions to the other water
molecules and fly away from the cup of
water. These molecules have become part of the gas
in the room. As you heat up the cup of water,
the molecules of water in the cup all start
moving, vibrating, and spinning faster and
faster. More and more molecules have enough
speed to escape the liquid water and become gas.
Finally, at 100°C, all of the molecules in the cup
are moving fast enough to escape the liquid, and
the liquid all boils away into gas.
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