AirAir

WALT: to know some of the WALT: to know some of the characteristics of aircharacteristics of air

WILF: to understand that air WILF: to understand that air exerts pressureexerts pressure

AirAir

Air is a mixture of different gasesAir is a mixture of different gases Including nitrogen, oxygen, carbon Including nitrogen, oxygen, carbon

dioxide, water vapourdioxide, water vapour There are other gases that are useful There are other gases that are useful

but come in very small quantitiesbut come in very small quantities

Air is important in allowing Air is important in allowing things to burnthings to burn

The oxygen in the air is needed to keep The oxygen in the air is needed to keep the fire going, but it is the fuel that is the fire going, but it is the fuel that is burning. burning.

Oxygen itself can’t burn. It has to combine Oxygen itself can’t burn. It has to combine with something elsewith something else

Why is oxygen only 21% of air?Why is oxygen only 21% of air? If it If it were any more, fires would break out were any more, fires would break out spontaneously all over, any dryness and spontaneously all over, any dryness and slight heating and, whoosh, up in flames. slight heating and, whoosh, up in flames.

Fish need air that is in water to Fish need air that is in water to livelive

Air can be Air can be squeezed into a squeezed into a balloon so that it balloon so that it pushes on the pushes on the rubber, stretching rubber, stretching it and making the it and making the balloon get biggerballoon get bigger

Oxygen could be described as our Oxygen could be described as our most important gasmost important gas

It supports the life of plants and It supports the life of plants and animalsanimals

Pure oxygen is also used to treat Pure oxygen is also used to treat patients with breathing difficulties, to patients with breathing difficulties, to support mountaineers and deep sea support mountaineers and deep sea diversdivers

Nitrogen is used in the food industryNitrogen is used in the food industry Many foods are packed in Many foods are packed in

atmosphere of nitrogen because this atmosphere of nitrogen because this stops the food “going off”stops the food “going off”

When you open a bag of crisps you When you open a bag of crisps you may be letting out nitrogen into the may be letting out nitrogen into the atmosphereatmosphere

Air PressureAir Pressure

Air pressure is all around us as we Air pressure is all around us as we live under a "sea of air" - a bit like a live under a "sea of air" - a bit like a fish surrounded by a sea of water. fish surrounded by a sea of water.

The air presses on us from all sides, The air presses on us from all sides, but we are so used to it we don't feel but we are so used to it we don't feel it. Every part of our body is pushing it. Every part of our body is pushing back (each cell is like a balloon) so back (each cell is like a balloon) so we don't get squashed flat. we don't get squashed flat.

ExperimentsExperiments

Target: what are we trying to find Target: what are we trying to find out?out?

To show that air exerts pressure or To show that air exerts pressure or forceforce

Experiment MaterialsExperiment Materials

What do you need?What do you need? A tank of waterA tank of water An empty drinking bottleAn empty drinking bottle A plastic bottle with a hole in itA plastic bottle with a hole in it Tumbler and a piece of paperTumbler and a piece of paper A strawA straw

Experiment 1Experiment 1

What is in this bottle?What is in this bottle? How can I prove that there is air in it?How can I prove that there is air in it? Lower it below the surface of the Lower it below the surface of the

water in the tankwater in the tank When the bottle is tilted bubbles are When the bottle is tilted bubbles are

forced out showing that air is presentforced out showing that air is present Pressure of the water forces the air Pressure of the water forces the air

outout

Experiment 2Experiment 2

Bottle with holeBottle with hole First of all we are going to fill it with First of all we are going to fill it with

water. What do you think will happen?water. What do you think will happen? Why?Why? The air pressure is pushing the water The air pressure is pushing the water

out of the holeout of the hole DemonstrationDemonstration

Now I cam going to put my hand over Now I cam going to put my hand over the top of the bottle. What do you the top of the bottle. What do you think will happen?think will happen?

Demonstrate- Why has this Demonstrate- Why has this happened?happened?

The air isn’t pushing down, the air The air isn’t pushing down, the air pressure is blocked so the water pressure is blocked so the water doesn’t come out the holedoesn’t come out the hole

You have a cup and piece of You have a cup and piece of paper. How can you put the paper. How can you put the paper in the water without paper in the water without

getting it wet?getting it wet? Screw a sheet of paper, putting it in Screw a sheet of paper, putting it in the tumbler so that it is a snug fit the tumbler so that it is a snug fit and won’t fall out of the tumblerand won’t fall out of the tumbler

Why does the paper stay dry?Why does the paper stay dry? The tumbler is full of air and the air The tumbler is full of air and the air

push is keeping the water from rising push is keeping the water from rising up inside the tumblerup inside the tumbler

Experiment 4Experiment 4

Take a straw and suck some water Take a straw and suck some water into itinto it

Hold it over a sink or container with Hold it over a sink or container with your finger firmly covering it upyour finger firmly covering it up

What do you think will happen?What do you think will happen? The water remains in the strawThe water remains in the straw Why?Why?

When your finger is not on the top of the When your finger is not on the top of the straw air pressure pushes down and up the straw air pressure pushes down and up the straw through both openings and so is straw through both openings and so is balancedbalanced

Gravity then makes the water fallGravity then makes the water fall If you block off the top of the straw, then air If you block off the top of the straw, then air

pressure can only push from the bottom.pressure can only push from the bottom. It is stronger than Earth’s gravity so it It is stronger than Earth’s gravity so it

keeps the water in the strawkeeps the water in the straw

Well done scientists!Well done scientists! Now for the write up!Now for the write up!