Very good question; the answer explains how a
hot air balloon works!
First, we start by saying that hot air, or
air with a higher temperature, is less dense than
cold air. What this means is that for a
little space, a lot more cold air particles can
fit in the space than hot air particles will fit.
Why is this?
Let’s think about a box with a lot of hot air
particles in it. When the air is hot, the
air particles have more velocity, and this
means the air particles hit each other and get
knocked around. This knocking around makes the air
particles want to spread out from each other,
because when each particle gets hit, it wants to
fly to an area where it won’t get hit. If the box
has a lot of cold air particles, then the
articles don’t move around so much, and
don’t mind getting hit by each other. The result
is that you can fit much more cold air
particles into a box than you can fit hot air
particles. When you count the mass of each
particle, this will tell you thata box filled
with hot air will weigh much less than the same
box filled with cold air. This is how we can
think of density; it is how much mass you
can fit into an amount of space, where right now
our space is a box.
Now if we take this example of a box, and apply
it to a ballon, we can figure out why hot stuff
rises. Stuff that is really dense likes to sink
to the bottom, while a material that is not
so dense will want to float to the top. This
is why a ship will always float on the sea, since
the ship is much less dense than water. Even
though the ship may be really big, its mass is
still more spread out amongst the ship, since its
density is small. Water, on the other hand, is
pretty heavy for a given amount of space, and very
stuffed into a small space, meaning it will sink
to the bottom.
This is the same with hot and cold air. The
dense, cold air will sink to the bottom, while
a balloon filled with hot air will rise to the
top. Note that we don’t care about how big the
balloon is, and only care about how hot it
is. I hope this answers your question!
Click Here to return to the search form.