THE AIR SHOW –

This show is all about the air around us and what we use it for. We need oxygen for burning or combustion and breathing or respiration.

Question - Which gas makes up the biggest percentage in the air?

Answer – nitrogen makes up ¾ of the air,

Carbon Dioxide (CO2) makes up only 0.04% of the air we breathe.

We saw solid carbon dioxide being put inside a rubber glove.  As it heated up to room temperature, the rubber glove expanded.  This is similar to what happens to your fingers in hot weather and why your rings may get tighter.

Oxygen (O2) makes up ¼ of the air we breathe.

A flame needs oxygen to continue to burn. We saw that if you fill a tube with neat oxygen and then put a recently extinguished match inside, it will re-light.  A lack of oxygen will put out a flame.

Show lit candle and put glass over it to put out flame.

Question - “What is inside a light bulb?”

Answer -  A gas called Argon

There are 6 inert gases (sometimes called noble gases):

Argon

Krypton

Xenon

Helium

Radon

Neon

A light bulb uses heat caused by an electrical current. When electrical current passes through the wire, it causes the wire to heat. The wire, or filament, gets so hot that it glows and gives off light. The light bulbs have a filament made of tungsten. Since the hot tungsten would quickly burn away if it were exposed to oxygen, it must be placed in a sealed glass bulb which is either empty or filled with a gas that won’t let it burn (see Inert gases below).

Pressure / Vacuum

The opposite of pressure is a vacuum.  Vacuum just means “nothingness”. We saw that it you stood in a plastic bag and used a vacuum cleaner to suck out the air, it stuck to our bodies.  This is because of the air pressure pushing on to the bag from the outside and not from the vacuum inside.

Fill glass with water and put card over the bottom and turn upside down.

This is because air pressure pushing upwards on the card is stronger is than the weight of the water pushing down.

 A scientist called Pascal showed that he could use a 10 metre length of glass tube full of water stretching the length of a ship’s mast, and the air pressure would still be strong enough to hold the card in place.

My Pet Vinnie

My pet Vinnie is very well trained and can swim to the top or bottom of a bottle on command.

Hold lid and squeeze and say “down vinnie, down”

Stop squeezing and say “ up vinnie, up”

Here’s how it’s done – the sachet floats because the sachet has air in it.  When you squeeze the bottle you put pressure on the water inside it that is stronger than the air pressure in the sachet which causes it to rise.

Magdeburgh Hemispheres

Air pressure was proven in 1651 by a man named Otto von Guericke in the town of Magdeburg. He invented a pump that was able to remove the air from an enclosed space. He then got a blacksmith to make two metal hemispheres about 1ft in diameter that fitted together (with a leather strap) to make an air-tight sphere.  Using his earlier invention he removed the air from the sphere. To everyone’s surprise, not only did the hemispheres remain stuck together after the air was removed, but it took over 2 teams of 8 horses pulling in opposite directions to separate them! Since air was removed from the inside of the hemispheres, the only thing that could have been holding the hemispheres together was the air on the outside pushing in on them. The pushing of the air is called air pressure.  There are 375 pounds of pressure on your hand at any one time.

A moving gas exerts less pressure than a stationery gas.

This is known as Bernoulli’s equation.  Bernoulli discovered that air that wasn’t moving pushed harder than air that was moving, after blowing over the top of a piece of paper and realising it went up instead of going down.

Blow on paper to show.

It is the principle by which an aeroplane works.  We recreated the “Bernoulli Blower” by placing an inflated balloon above the path of the heat from a hairdryer. The balloon is held in place by the air pressure surrounding itWhen the air balloon cools down it starts to drop in height.  The Bernoulli equation is how Montgolfier managed to invent the hot air balloon and how Christopher Cockerell managed to invent the Hovercraft in the 1950’s.  The Hovercraft is really hovering and does not touching the water below it.  The air beneath it acts as a lubricant.

Air is a conductor of sound

Blow hooter

Air is blown between the two wall of the hooter which makes the membrane (point to it) vibrate.

The vibration cause sound waves to travel through the air.