|How does water absorb heat?|
|Question Date: 2012-10-24|
Well, to understand the answer to this
question, we need to understand what "heat" is.
The general idea of "heat" is actually pretty
complicated, but for now, we can talk about it
this way: all the stuff in our everyday life is
made up of atoms. These atoms are constantly
vibrating and jostling around, and "heat" is the
energy contained in this vibrating. So, the
hotter something is, the more strongly the atoms
it's made of are moving around.
Now we can talk about heat transfer. One
method of heat transfer is conduction: let's say
we have something really hot (so its atoms are
vibrating really fast) and touch it to something
colder (whose atoms are vibrating more slowly).
Then as the atoms in the hotter object vibrate,
they'll hit the atoms in the colder object, and
make them start vibrating more. As this
happens, the hotter object cools down, and the
cooler object warms up. This is how, say, water
in a pot on a stove absorbs heat: the stove
heats up the bottom of the pan, and that heat is
conducted into the water in the pot.
Another form of heat transfer is radiation.
You may know that atoms are made of electrons
(and other stuff), and that electrons create
electric fields. Well, as the atoms in
something vibrate, the electrons vibrate too,
and this vibration creates waves of what's
called electromagnetic radiation. Depending on
how quickly the atoms are vibrating (so how how
something is), the electromagnetic radiation can
be what we know as radio waves, microwaves,
visible light, X-rays, and so on. Now, if this
radiation hits some other stuff, the reverse
process can happen: the electromagnetic
radiation hits the electrons in some material,
and that makes the electrons vibrate, which
makes the atoms vibrate, which makes the
material hotter. This is how the radiation that
the sun emits can heat up the Earth, even though
the Earth and the sun are really far apart!
This is also another way that water can absorb
I hope that helps!
First, we need a molecular picture of what
(similar to all substances) is composed of tiny
billiard balls on a pool table. When the
molecules have a lot of
energy, they bounce around at high speeds and
slower-moving objects around them, transferring
some of their energy.
At large lengths, this would be water vapor.
When the molecules are moving very slowly,
attractive forces between
them pull molecules together into a tight
crystal shape. This state is
ice. In between these two extremes (at room
temperature), liquid water
molecules move slow enough to feel attracted to
nearby molecules, but
fast enough to be able to easily move around.
To answer your question, you can think of
water absorbing heat like
the break in a game of pool. A fast moving
molecule (the cue ball)
strikes a lattice of slow moving ice or water
molecules. The cue ball
rapidly decelerates (is cooled) as the rest of
the balls jumble around
the board in a liquid or gas-like state.
Water absorbs heat by vibrating and rotating.
The vibrations can be the stretching or bending
of the chemical bonds between hydrogen and
This a good question, and it's related to
the concept of thermal equilibrium.
Thermal equilibrium means that when we have
two bodies in contact with one another, they
will exchange energy until their temperatures
are the same. in this example, we can think of
air and water as the two bodies that are in
contact and exchanging energy.
One important thing to keep in mind is that heat
is a transfer of energy. So when the system
tries to achieve thermal equilibrium between the
air and water, heat is the process that's making
it happen. If the water is cooler than the air,
then heat energy will "flow" from the air into
the water until the temperatures are equal.
Water can absorb a very large amount of heat
and only a small increase in its overall
temperature. This property of water, its high
heat capacity, is part of what allows life as we
know it to exist on this planet by regulating
global climate. Water has a high heat capacity
(an ability to absorb heat) because for water to
increase in temperature, water molecules must be
made to move faster within the water; doing this
requires breaking hydrogen bonds (the
H2 in H2O) and the
breaking of hydrogen bonds absorbs heat. With a
such a high heat capacity, a lot of heat energy
can enter a body of water before the water
actually increases in temperature. This is why
it takes water so long to boil!
Matter of any kind absorbs heat. Water is no
Water is particularly good at it because of
the way that hydrogen atoms in one molecule can
form temporary bonds with oxygen atoms of
another molecule. The process is
called "hydrogen bonding". Most of the bizarre
properties of water stem from this fact (e.g.
liquid at room conditions, solid form [ice] is
less dense than liquid form, and can absorb a
tremendous amount of energy without warming up
An object absorbs heat in a number of different
ways. One way is by
radiation... so, when you shine a light (Sun!
on a rock, the photons
making up the rays of light impinge on the atoms
in the rock. This
causes the atoms in the rock to VIBRATE faster
because they have
more energy (photon energy converted to
higher rate of vibration is what we sense as
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