Accessing a video of a meteor exploding as it enters the atmosphere would be helpful, e.g. the Chelyabinsk Meteor which exploded over the Urals in Russia in February 2013. Download here or watch online at: https://goo.gl/xbFisl
Show the video of a meteorite exploding far up in the sky. Discuss why the meteorite travelled a long distance through outer space (a vacuum) without exploding, and why it did not wait to explode until it hit the Earth’s surface (it hit the atmosphere). Ask the students to offer some possible explanations.
Other discussions could be based around air being necessary for us to breathe and stay alive; astronauts carrying oxygen with them into space. Can they think of other objects in which air is stored? (tyres of bikes and cars, bubbles, footballs).
Suggested trigger questions:
- Can you see air? Smell it/ feel it /taste it? (Probably not. But you can hear and feel moving air, e.g. on a windy day or near a fan. And you can see air if there are impurities in it? (e.g. dust in sunlight or smoke).
- If you take everything (i.e. all the people and all the objects) out of this room, what is left? (Nothing? Are you sure?).
Note: Students test out the following activities individually or in small groups. Students should discuss in small groups or write down what they think is happening in each activity.
Activity 1: Fill a Balloon with Air
Take a balloon and blow it up (i.e. fill it with air but do not let it explode).
Can you describe what is happening? (As the air enters the balloon from your lungs, it takes up space in the balloon. The balloon expands because the air inside needs more space).
Activity 2: Fill a Syringe with Air and Feel the Air Pushing
Pull the plunger of the syringe out towards you, then push it in again. Was this easy? What was happening inside the syringe? (The syringe was filled with air, which was pushed out again).
Pull the plunger again, and this time cover the other end of the syringe with your finger. Press down on the plunger. Was this easy? What did you feel? Can you explain what was happening inside the syringe? Was there any difference this time, and if so why? (It is easy to push the plunger a little, but gets difficult because the air trapped inside the syringe resists the plunger. The more compressed the air becomes, the harder it is to push the plunger).
Let the plunger go. What happens? (The plunger pops back and then stops). Why do you think this happens? (The air which was compressed in the syringe expands to its original state and pushes the plunger back out).
Activity 3: Controlling Movement with a Syringe Attached to Each End of Plastic Tubing.
For the following, use 2 syringes of the same size.
Push the end of one syringe fully in, and attach the tubing to it.
Push the end of the other syringe only partially, and attach the tubing to it. (This is to make sure that the syringes are not pushed out of the tubing).
Predict what will happen to the other syringe when you push one syringe in and out? Now try and see! (The other syringe moves out).
Why does this happen? (The trapped air has the power to move things).
Can you compare how much both the syringes moved? (Approximately the same).
Repeat the above activity using two different sized syringes.
Do you think the syringes will move the same distance this time? Try and see! What do you notice? Is there any connection between the size of the syringes and the distances they move? (A small syringe pushes a bigger syringe by a small distance. A large syringe can push a small syringe by a much greater distance).
Activity 4: Fill a Straw with Water from the Top
Block up the bottom of a narrow straw with a piece of Blu tack. Then fill the straw with water from the top, using a pipette. Was this difficult? If so, why do you think it was not easy? (Air got in the way). Slowly release the Blu tack. What happens and why? (The water moves down, because the air escapes).
Activity 5: Dry Tissue under Water
Crumple up some tissues into a ball and push them tightly into the bottom of a cup, so that they do not fall out when the cup is turned upside down. (A few tissues tightly packed are less likely to fall out than one tissue). Predict what will happen to the water and tissue when you turn the cup upside down in the water.
Now turn the cup upside down and place it in water contained in a bowl. Take it out and feel the tissue. What do you notice? Why do you think the tissue did not get wet? (Air prevented the water from going up into the cup).
Discuss where air pockets can occur: in water pipes, capsized canoes, central heating radiators, etc.
Discuss what a vacuum is.
What do you call the layer of air surrounding the Earth? (The atmosphere).
What happens when things crash into the atmosphere? (Discussion could include the heat caused by friction. Students can rub or clap their hands – what do they feel? Planes catch fire when they crash because of the intense heat).
Think of spacecraft returning to the Earth at a high speed after a mission in Space, what do they encounter first? (Air, i.e. the atmosphere). What you think it has to do? (Slow down). Otherwise what would happen? (It would break and burn up).
How do you think a spacecraft can be prevented from burning up? (It is covered in insulating materials, and also it slows down).
Safety: In Activity 3, always use sterile syringes that have not been used for medical purposes. Be careful with the sizes of syringes – a big syringe could push out a small syringe with great force.
Maths: Display these questions for the students to answer.
1) Air is a mixture of gases that consists of carbon dioxide, argon and very small amounts of other gases.
- Approximately what percentage of the air consists of (i) nitrogen and (ii) oxygen?
- What is the approximate ratio of nitrogen to oxygen in the air?
- Can you convert the three percentages above to decimals?
2) In Activity 3, use two different-sized syringes connected by tubing, calculate the ratio of the sizes of syringes. Then measure the distances that the two syringes moved.
- Is there any connection between these two ratios?
- Investigate which combination of syringes gives the greatest movement.
Analysis/Conclusion: Air takes up space (even though you cannot see it).
Follow-up activity: Filling a Bottle Using a Funnel
Put the funnel into the mouth of the bottle and ask the students to predict what will happen when they pour water into the funnel.
Ask them to pour water into the funnel and observe what happens (The water fills the bottle).
Now, secure the funnel to the bottle such that there is no space between the two. THIS SPACE MUST BE TOTALLY AIRTIGHT. The students again predict what will happen when they pour water into the funnel. They then pour water into the funnel.
Note: It can be difficult to get an airtight seal. A rubber O-ring, available in DIY stores, placed around the neck of the funnel and then pressing down on the funnel by hand can produce a good seal. Tape, well-sealed, may work also).
Observe what happens. What do you see? What do you hear? Why was it hard for the water to enter? (Air inside the bottle got in the way). What else do you notice? (In case of a fully airtight seal, no water will enter the bottle because the air gets in the way and cannot escape. If there is a slight air leak, there is a glug- glug sound of some water getting in while bubbles of air escape).
- Find out more about central heating radiators not giving out much heat because of air getting trapped in them – ‘air locks’, and how this air is released.
- Explore the five different layers which make up the atmosphere – find out their names, and at what approximate level you will find clouds, aeroplanes, the ozone layer, satellites, the International Space Station, etc. See the additional information section for links.
Did You Know?
- In October 2014 Space X Dragon Spacecraft, returning to the Earth carrying a cargo of biological samples (including plants grown in space) from the International Space Station, produced intense heat as it entered the atmosphere. The temperature was nearly 3000º Fahrenheit (1649ºCelsius). It was protected from burning by a very strong heat shield.
Image credit: NASA/SpaceX
- On Monday, 19 January 2015 an amateur photographer captured a fireball over Dalkey Island, south Co. Dublin. (Photo in Irish Examiner on Tues 20 January 2015).
“It is definitely a fireball or bright meteor,” confirmed David Moore the editor of the Astronomy Ireland magazine. “These objects come through the atmosphere at 70,000mph, burning up as they enter and are extremely rare to photograph.”
- A fisherman survived 60 hours in an air pocket under an upturned boat which capsized off the coast of Nigeria in May 2013.