What do we know about air? What have we observed?

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4 Air and Flight---Properties of Air Air: - we know it exists, - it s all around us, - we see moving trees, - it fills our lungs, - it has substance but can t be seen Air: - colourless, odourless and tasteless, - a gas made mainly of nitrogen (78%), oxygen (21%) and small amounts of carbon dioxide, hydrogen and other gases - we can t taste it, but - we can feel it. What do we know about air? What have we observed? Air is matter so it must be made up of molecules and atoms. It interacts with objects because we can see the trees swaying in the breeze. We also know it moves things since we can see the clouds moving in the sky and storms approaching us in the distance. We know that the air must move because it brings us our weather. Air can change temperature - we can feel the temperature of the air against our skin. Sometimes air can smell. It is able to carry the smell of roses to our noses or for that matter an angry skunk, too. We know that hot air rises and that hot air can hold more moisture. We see birds using the air to travel from place to place and we also see seeds being blown around by the wind. We know that the air can become quite dirty from dust but also quite polluted. Sometimes we can see the pollution or smell the pollution. We know that air must take up space because we have all blown up a balloon or put air in our bicycle tires.

5 AIR TAKES UP SPACE PROPERTIES OF AIR straight MATERIALS: -2 glasses, -large container to hold water (aquarium, sink) STEPS 1-Take two glasses. 2-Place glass#1 straight down into the water tank. 3-Place the 2 nd glass tilted in the water tank and let it fill up with water. When full, bring it up and face down and as close to the surface without removing it from the water. 4- Tilt glass #1 so that you see bubbles escaping the glass. 5- Try to capture the air bubbles in the second glass and observe. glass1 WHAT HAPPENED? (OBSERVATIONS) Air bubbles glass2 Explain what happened to the water in the second glass?

6 AIR TAKES UP SPACE MATERIALS: glasses, large container to hold water (aquarium, sink), crumpled paper or washcloth, tape, flexible straws EXPERIMENT A: 1. Crumple a piece of paper or small washcloth into the bottom of a plastic cup (tape may have to be used to keep the paper at the bottom of the cup). 2. Turn the cup straight over and submerge it straight under the water. 3. Remove the cup straight out of the water. WHAT HAPPENED? (OBSERVATIONS) PROPERTIES OF AIR Why didn't the paper inside the glass get wet? EXPERIMENT B: 1. Turn a glass straight over and submerge it straight under the water 2. While under the water tilt the cup slightly to allow some air to escape and water to rush in. Then place the cup back in a straight upside-down position. 3. Slip one end of the flexible straw under and inside the glass, while the other protrudes above the surface of the water. 4. Blow through the straw while your partner holds the glass steady. WHAT HAPPENED? (OBSERVATIONS) straw glass Explain what happened to the water in the glass?

7 AIR RESISTS THINGS MOVING THROUGH IT- PROPERTIES OF AIR crumpled Steps: 1- Get 2 pieces of paper identical in weight an size. 2-Crumple one of them. 3-Now, at the same time and from the same height, drop them. 4-You can see that they don t hit the ground first. Results: (Circle the best answer) Which one hits the ground first? Why? A-The paper is heavier after it is crumbled, so it fails to the ground before the intact paper. B-The crumpled paper has less area for air to resist and falls the ground before the intact paper. C-The crumpled paper has less area for air to resist, and fall to the ground after the intact paper. Which events show that air resists things moving through it? (Circle the best answer) A- Leaves fall slowly to the ground B-A book is put on a blown-up balloon. C- A parachutist jumps from a plane with a parachute. D-A plastic bag filled with air is poked. intact

8 AIR PRESSES ON THINGS-PROPERTIES OF AIR Materials: -A glass with smooth rim -a glossy card(deck of cards) -water Procedures: 1-Fill the glass of the rim with water. 2-Place the glossy side of the card down on the rim of the glass. 3-Keep the palm of your hand on the card and turn the glass upside down. 4-Take your hand away from the card. Results: Explain:

9 AIR PRESSES ON THINGS-PROPERTIES OF AIR Materials: -A glass with smooth rim -a glossy card(deck of cards) -water Procedures: 1-Fill the glass of the rim with water. 2-Place the glossy side of the card down on the rim of the glass. 3-Keep the palm of your hand on the card and turn the glass upside down. 4-Take your hand away from the card. Results: Explain: The card remains attached to the rim of the glass. The water does not fall out. Why? The air pressure exerted on the card from underneath is greater than the weight of the water in the glass. This is why the card can hold the water in the glass.

10 AIR EXPANDS WHEN HEATED PROPERTIES OF AIR Material: -Ping pong ball -Glass -hot water Steps: 1-Have a glass of hot water ready. 2-Put a deformed table tennis ball in the glass. Why does this happen? Results: Explain: Experiment-Properties of Air AIR HAS WEIGHT Steps: 1- Inflate two balloons to about the same size and tie them each with a string. 2-Put a tape on one of the balloons. 3-Tie them each at the end of the rod to make a scale. 4-Poke a little hole on the tape with a pin. Results- One end of the scale weighs down. Explain- Why does this happen?

11 AIR HAS PRESSURE PROPERTIES OF AIR STEPS 1- Lay a ruler on a table so that about one third of it lies over the edge. Material -ruler -table -newspaper 2- Spread and smooth a piece of paper over the ruler. 3-Now try to make the paper fly into the air by hitting the ruler downward with a fast and hard motion. WHAT HAPPENED? (OBSERVATIONS) Explain- Why does this happen? The student will not be able to lift the paper because air has weight and is pressing down on it. The surface of the paper is large, and therefore there is enough force due to the air pressure on it to prevent it from being moved by the force applied to the ruler. Interesting Science Facts The higher you are in the sky, the less air there is pressing down on you. That is why air pressure is higher at sea level than at the top of a mountain.

12 AIR HAS PRESSURE PROPERTIES OF AIR STEPS 1- Lay a ruler on a table so that about one third of it lies over the edge. Material -ruler -table -newspaper 2- Spread and smooth a piece of paper over the ruler. 3-Now try to make the paper fly into the air by hitting the ruler downward with a fast and hard motion. WHAT HAPPENED? (OBSERVATIONS) Explain- Why does this happen? Interesting Science Facts The higher you are in the sky, the less air there is pressing down on you. That is why air pressure is higher at sea level than at the top of a mountain.

13 AIR EXPANDS WHEN HEATED PROPERTIES OF AIR Material: -kettle -ice -bottle -balloon STEPS 1. Stretch out a balloon and place its open end over the mouth of a plastic pop bottle. 2. The bottle is then submerged in the hot water container and is observed. WHAT HAPPENED? (OBSERVATIONS) Explain- Why does this happen? AIR COMPRESSES WHEN COOLED PROPERTIES OF AIR 3. Next, the bottle is placed into the ice cold water and is observed. WHAT HAPPENED? (OBSERVATIONS) Explain- Why does this happen?

14 AIR EXPANDS WHEN HEATED PROPERTIES OF AIR Material: -kettle -ice -bottle -balloon STEPS 1. Stretch out a balloon and place its open end over the mouth of a plastic pop bottle. 2. The bottle is then submerged in the hot water container and is observed. WHAT HAPPENED? (OBSERVATIONS) Explain- Why does this happen? Air expands when heated because the molecules are further apart. This also has the effect of making warm air lighter. AIR COMPRESSES WHEN COOLED PROPERTIES OF AIR 3. Next, the bottle is placed into the ice cold water and is observed. WHAT HAPPENED? (OBSERVATIONS) Explain- Why does this happen? Air compresses when cooled because the molecules are closer together. This also has the effect of making cold air heavier.

15 PROPERTIES OF AIR Fill in the blanks with the given words. Two qualities of air enable us to use it as a useful tool. Air can be 1. and air can act as an 2. Conserve More Compressed Insulator Air is compressed when more than the regular amount of air has been pushed into a container. More air in the same space exerts 3- pressure. Air acts as an insulator when it helps 4- heat. The fur of my dog works in this way by trapping air to keep itself warm. A Write the letters in the correct boxes. B C Sleeping bag Fire extinguisher mittens D E F tire Spray can Double paned window Compressibility Insulating quality

16 Match each fact with the property of air. Write the letter. Properties of Air a) Air has weight (mass). b) Air takes up space. c) Air presses on things. d) Air can be compressed. e) Air resists things moving through it. f) Air expands when heated. g) Air has insulating quality. Air Facts 1. A flat car tire is lighter than when it was full of air. 2. A flat piece of paper falls slower to the ground than a crumpled piece of paper. 3. Air molecules move around and spread out when heated. 4. Air expands to fill a container, but we may still put more air in it. 5. A feather down coat traps air within it. It keeps the warmth in and the cold out. 6. An empty water bottle immersed in water upside down will not fill with water because it is already full of air. 7. A card placed over the rim of a cup of water will hold the water in place while the cup is upside down. The only thing holding the card in place is the air underneath the card.

17 FLIGHT Four Forces of Flight Before a person can understand flight, they must first learn about the forces that control flying. A force is a push or a pull in any direction. Gravity Force Gravity is an invisible force which pulls objects together. Objects with a large mass pull and attract objects with less mass. Because the earth has a very large mass, all objects near it are pulled towards the center of the earth. This downwards pull Is called the force of gravity and works against things that are trying to fly. Drag Force Drag is a force that slows you down and works in the opposite direction than you are travelling. For example, when a parachute on a dragster opens up after the race, it creates a drag force that helps to slow the car down. Lift Lift is a force upward. If the lift force is greater than the gravity force, the object will stay In the air. Thrust This is the force that moves an airplane forward and is usually produced by a plane s engines. forward

18 What is FORCE?

19 Floating and Sinking in Fluid Air By now, you can probably name many materials that are natural floaters in water. You also know that materials which are natural sinkers can be made to float. All it takes is a little reshaping so they hold lots of air. But a natural floater in one fluid may be a natural sinker in another. This is certainly true for air. The upward buoyant force that air exerts on objects is usually too small to balance the downward force of gravity on them. So even an air-filled balloon will sink in air. In fact, only a few materials are able to float in air. One material that floats in air is hotter air! If you measured equal volumes of hot and cold air on a balance, you would find that the hot air has less mass than the cold air. That means hot air can float up through cold air. And that means it s possible to help air sinkers become air floaters. This is what two brothers did in 1783, when they designed, built, and successfully launched the world s first hot-air balloon. The first hot-air balloon was launched near Paris, France in It had a mass of more than 600 kg. Even so, the balloon could hold enough hot air to lift off and float in the air for 10 minutes before returning to the ground about I km away. A huge straw fire was built under the open end of the balloon to supply hot air.

20 Experimenting With a Helium Balloon Attach paper clips to the string on your helium balloon to alter the balloon s mass and density. Predict and record the number of paper clips required to float the balloon at different heights above the ground. 1. Why do helium balloons float in air? 2. How did you control the height at which the balloon floated? 3. If the air in our classroom was much warmer, would it change the number of paper clips required to sink the helium balloons? Explain.

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22 LIFT vs GRAVITY Sir Isaac Newton, an English scientist, observed the force of gravity when he was sitting under a tree and an apple fell on his head! It is a strong force that pulls everything down toward the earth. The more mass, the more gravity pulls. The lighter the object the less lift required to make it buoyant (able to float on air). Jump up into the air and stay there! What happens? Do you know of any place that does not have gravity or much less gravity? Drop a pencil, rock and a ball. What happens? What does this mean for bigger and heavier airplanes? When you lift things up you have to pull against gravity. If you drop a pencil, gravity pulls it to Earth. If you rest its mid-point on your finger, gravity will pull down equally on both sides of the pencil and it will balance in the air. The attractive force of gravity acts between at the center of two objects. In the case of people standing on the earth s surface, the effect of gravity is to attract us towards the center of the earth. As a result, no matter where you stand on the earth, you don t fall off. Gravity is also the reason why the moon (and satellites) orbit the earth and why we orbit the sun. Lift is the upward force used to overcome gravity and to achieve flight. Lift occurs if the force on the bottom of an object is greater than the force of gravity from above. To sustain a particular height, lift must equal gravity).

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26 Laws of Flight 1-Bernoulli s Law of Pressure: The faster air flows, the less pressure it has. When air is moving, It creates areas of high pressure and areas of low pressure. Fast moving air creates an area of low pressure because the particles are spread further apart while high pressure air has particles packed closer together. 2-Law of Flight: Objects always go from high pressure to low pressure. A good example of this happens when a hole is made in the body a passenger plane. The air in the plane is under high pressure to keep passengers comfortable compared to the low pressure air outside. When a hole is made in the body of the plane, objects in the high pressure plane move violently towards the low pressure air outside often resulting disasters. 3-Newton s Third Law: This law says that if there Is a force in one direction, there is an equal force In the opposite director. For example, when a person on a skateboard pushes backwards on the ground, they move forward. This law helps to explain how rockets and jet engines work.

27 WHAT WILL HAPPEN? For each of the following: Predict what you think will happen Perform the experiment Draw and describe what you saw happen Try to explain why this happened 1. Blow over top of a piece of paper 2. Blow under a suspended piece of paper 3. Blow under a folded index card 4. Blow between 2 cups

28 5. Blow into the bottom of a funnel that has a ping pong ball in it 6. Blow through a straw that is over another straw that is in a cup of water 7. Hairdryer blowing straight up at a ping pong ball 8. Can you think of a real world example, and/or how this relates to flight?

29 The Wing The picture below shows a side view of a bird s wing which is similar to the wing of a glider, airplane or helicopter blade. 1) When air hits the front of the wing (leading edge) it splits up. 2) The air flowing over the curved top of the wing has further to go than the air going under the flat bottom of the wing. 3) For the two streams of air to reach the back of the wing (trailing edge) at the same time, the top stream must travel faster than the bottom. (It has further to go) 4) This fast moving air creates a low pressure area on the top of the wing and a high pressure area on the bottom of the wing. (Bernoulli s Law) 5) Since objects tend to go from high pressure to low pressure, lift is created, which is how birds and planes stay in the air. (Note that for the wing to have lift, it must be moving forward through the air)

30 2. Draw a diagram of how air moves over and under an airplane wing 3. Why do airplanes take off and land into the wind?

31 Bernoulli s Principle Draw a labeled diagram of one of the investigations showing Bernoulli s Principle. Describe what happened in this investigation. Include these words in your explanation: air low pressure exert force stationary moving high pressure