Hello I am back with some more experiments on the idea that warm air rises, and this one is
going to be interactive fun. We are going to make a hot air balloon using birthday candles, tape, scissors,
bundle of straws, and a plastic bag, and that is our hot-air balloon. So, first we need to make
our structural supports out of straws, and all I am going to do is I am going to need to attach
straws together, and I am actually going to use straws to do that. So, I am going to snip off a little
section of straw. That is going to be my splice, and to make the straw fit I am just taking a scissors
and slitting the ends of that straw so that it can more easily go into the other straws. Take
another straw, roll it up, insert that, you are going to notice I have it fitted together. The next one I am
going to insert this. Now I am going to just measure it out, so I have forty centimeters on my meter
stick, here. Hold it up, mark where 40 is, snip the end, and now I have a 1. Let us make another one, I
have to join these together as an X, so I am going to find the halfway point using my meter ruler, that is
20. Great mathematicians go with science. Take a little bit of tape, and now I am going to form
my X and I am just going to wrap the center of my X with the tape. So far there, nothing tricky
here, in fact kids may be able to handle this, snipping straws, taping them together, you
want to make sure it is stable, now all I have to do is attach it to my bag. So I have
my bag opening, you are going to spread it. What I am going to do here is just wrap the little bit of
the bag around my straw... tape. You do not want to go crazy with the tape, the lighter this
bag balloon is, the better. Okay, go to my opposite opening here, more tape, a little bit,
slide it up to the end, all I am doing is catching the bag and the straw with my tape
and wrapping it around, and almost there, stretch my bag opening out... I just attach the last two.
Obviously, a real hot air balloon is tethered by ropes, this is just going to hold our bag open,
last piece of tape wrapped around the straw, a little bit of straw hanging over where I
wrap the tape around, and you will see I now have my hot air balloon structure. Thanks for
watching. Back with part two for our hot air balloon experiment using birthday candles.
What candles to use? We want to use the smallest candles possible, you can see I have two here. We
want to go with the smaller one, these are actually two and a half inches by a quarter
inch, and all I have is a four by four inch square of aluminum. It is just aluminum foil
cut out, and this is the tricky part - I have to attach my candles to my aluminum, and to do
that I am going to heat up the end of this candle until it is soft and pliable, and then attach it
to the tinfoil. Notice I have my safety glasses on for protection so I am going to heat the end
here using my burner just till it is soft, and I am going to hold it till it secures. That is one,
you do not want to burn your fingers, too, if they pop off, no big problem, we can simply
attach them again, and they probably will fall off at one point or another. There is three, yep,
there you go, see, it fell - if you do not hold it long enough, it will fall over. You can blow on
it a little bit, there holding nicely... and number four, and I am going to let that dry... I have it all
complete. The next part, and we want to make sure the wax is totally dry and set up.
We need to attach it to our balloon, we made our burner previously, we made our balloon. Now
it is time to put them together, so we are going to flip this over. You want to be careful, the
candle should still stay attached through the aluminum foil. It is the beauty of wax, and very
carefully I am going to attach this aluminum foil to my straw structure, just with some tape
again, do not go crazy with the tape, we want this to be as light as possible so that we have lift
to our balloon. A lot of safety features to think about here that we are going to highlight later, but
it is a really a neat experiment for kids to see that warm air rises, so I have it attached and
you can see the candles through the bag, and now we are going to fly this thing so I am just going to peek
up under here so I can see what I am doing. It is a little bit awkward trying to get this on camera,
I got them lit, and what is going to happen is that those candles are going to start to heat the air up
and that warm air is going to fill this bag and I am going to let it set on the table, and this is where
you have to have patience right now. That warm air is filling the bag just like a hot air balloon, a hot
air balloon uses giant burners that shoot that hot air up in. This is using birthday candles so
it is going to take some time but you are going to eventually see the bottom start to lift off of the
table. That warm air is rising, those air molecules are spreading out, they are becoming less dense, and
you can see we have some movement here. Houston we do not quite have liftoff, but we have movement and
it is pretty cool when you see this thing take off. It is going to rise to the ceiling, because warm
air rises. We have movement here, I do not want to lift it, and you see this thing is starting to take
off, now. The air currents in the room are going to push this thing all over, but that is a hot air
balloon if I have ever seen one. It is not going to lift me up, you can see as it bangs the ceiling
it pushes some of the hot air out, and you will see it drop a little bit, it is going to float over here
now, if I were doing this in an auditorium or a gym where the ceilings are 40 feet high you are
going to want to tether this, the cool thing about this is the wax is only going to fall on
the tinfoil. If the candle were to break loose and fall it would blow itself out. That is the beauty of
using birthday candles, now this is a cool birthday cake. Sing happy birthday, the magic is going to happen,
when I blow these candles out, and you will watch as the air cools down. It is going to sink, so here we go.
It is losing its lift, the cold air does not want to rise, it wants to sink it is
still filling the bag, you are going to see the bag start to collapse, as the air cools
down, because cold air sinks, warm air rises. How cool is this? It is science! Thanks for watching.