Answer 1:
An excellent question!
Producing steam is converting a liquid to a gas
and would involve a a large volume expansion.
When you talk about evaporation and boiling, you
are talking about two different processes. You can
read more about the different between the two
here
Evaporation occurs only at the surface and
happens at any temperature. For any
temperature below 100 degrees Celsius and at 1
atm, higher temperatures will lead to more
evaporation and some expansion of volume. However,
the volume expansion is not as large as converting
water to steam. Evaporation is also
counterbalanced by condensation and is dominant at
temperatures below the boiling point. As it
occurs mostly at lower temperatures, it would not
lead to as great a volume expansion.
We can understand this first part of volume
expansion upon boiling by thinking of steam (a
vapor at high temperature) as an ideal gas (not a
totally correct picture, but it will illustrate
how to think through the problem). The ideal gas
law can be derived using thermodynamics and has
the form PV = nRT, where P is the
pressure, V is the volume, n is the
number moles of the species you have, R is
gas constant, and T is temperature. What is
ideal gas law tells you pressure and volume are
inversely proportional, but pressure and volume
are proportional to temperature. For example, the
same amount of gas (in moles) n in a
smaller container will result in a larger
pressure. Another example is a higher temperature
will increase the kinetic energy of the gas
particles and cause them to collide with the sides
of the container more frequently and at a higher
velocity, which corresponds directly to a
pressure. Similarly, keeping the pressure constant
would require a larger volume container for
increasing temperature.
More generally, the state of water depends
on both temperature and pressure. The common
temperatures we know ice and vapor to form are
only true for atmospheric pressure, which is the
pressure most everyday things happen.
Phase diagram of water
People have figured out using thermodynamics the
dependence of phase (what you call the state of
water) on temperature and pressure, and put them
on graphs called phase diagrams. A phase diagram
for water can be found
here
By picking a particular temperature and pressure,
you can figure out what phase water is.
If you are interested in what the different
features of the phase diagram means, you can read
more about it
here
Basically, the lines that separate the regions of
ice, water, and vapor are lines of two-phase
coexistence. That means at temperatures and
pressures along the boundary between water and
ice, both water and ice can be found at the same
time with each other. The triple point is
where all the phase boundaries intersect and marks
a special temperature and pressure where all three
phases exist in equilibrium.
Answering the last question, the phase you get
really depends on which temperature and pressure
you are in. For example, we generally associate
the boiling temperature of water to be at 100
degrees C, but this is specific to a pressure of 1
atm (i.e., the pressure around sea level). If you
were at higher pressures, you would need higher
temperatures to boil the water. This is the idea
behind pressure cookers, for instance.
Hope this helps!
Best,
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