E Chemistry Sciences: C. Atmospheric Properties Activity: Fluid Investigations

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1 Science as Inquiry: As a result of activities in grades 5-8, all students should develop Understanding about scientific inquiry. Abilities necessary to do scientific inquiry: identify questions, design an investigation, collect and interpret data, use evidence, think critically, analyze and predict, communicate, and use mathematics. Source: National Science Education Standards NSES Standards for Grades 5-8: Structure of the Earth System The atmosphere is a mixture of nitrogen, oxygen, and trace gases that include water vapor. The atmosphere has different properties at different elevations. NCTM Expectations: Represent, analyze, and generalize a variety of patterns with tables, graphs, words, and when possible, symbolic rules. Solve problems involving scale factors, using ratio and proportion. E Chemistry Sciences: C. Atmospheric Properties 1

2 Science Process Skills: Investigating Comparing Interpreting Recording data Inferring Hypothesizing Math Process Skills: Counting Comparing Graphing Objective: The learner will determine there are a number of characteristic properties of air including mass, weight, density, volume, and pressure. The learner will identify gases and their proportions that make up the Earth s atmosphere. The learner will categorize air as a fluid, similar to the ocean, based on observable properties. Time: 75 Minutes Materials: Globe Thin sheet of bubble wrap Bowling ball (or other 14.7 lb object) Balloon Measuring tape Aquarium with water 2 glass flasks Student Materials: Per Student Tornado Tube coupler 2 empty 2 L soda bottles Colored water Per Pair of Students Bag of 100 items of 3 colors, proportionate to atmospheric gases (nitrogen: blue, oxygen: red, hydrogen: white) Small tray or paper plate Mini-bell jar with tubing and syringe Large marshmallow Per Group of 4 Students Empty 2 L soda bottle Pressurizing valve bottle pumper Digital scale E Chemistry Sciences: C. Atmospheric Properties 2

3 Instructor Preparation : Fluid Investigations Activity Prepare bags of beads (or other items) with 78 blue beads to represent nitrogen gas molecules, 21 red beads to represent oxygen molecules, and 1 additional bead of white to represent the water vapor and trace gases in the atmosphere. Put together tornado tubes with colored water approximately 2/3 full in one bottle and an empty bottle on top. Have materials organized on trays or in tubs and ready to distribute during the lesson. E Chemistry Sciences: C. Atmospheric Properties 3

4 Instructor Background Information: Note: Students may assume that because humans need oxygen and we get oxygen from air, that oxygen gas must be the primary component of Earth s atmosphere. In fact, nitrogen gas (N 2 ) is the main component of the atmosphere. Oxygen gas (O 2 ) is the next largest component. Other gases such as carbon dioxide (CO 2 ) and argon (Ar) each makes up less than 1% of the atmosphere. An atmosphere is a layer of gases that surrounds a planet. Earth s atmosphere is usually referred to as air. What is Earth s atmosphere made of? Earth s atmosphere is currently composed of two main gases: nitrogen (N 2 ) and oxygen (O 2 ).Together, these componenets make up about 99% of the particles in the atmosphere. The remaining 1% of the atmosphere consists of trace gases such as argon, carbon dioxide, neon, ozone, and other minor components. You may wonder where water fits into the mix. The composition of the atmosphere is usually stated in terms of the composition of dry air. Dry air refers to air with little relative humidity, or a very small amount of water vapor. Water vapor (the gaseous state of water) is a component of Earth s atmosphere, but it varies significantly, from about 1% to 7%, depending on season and location. Even air that is considered dry will have trace amounts of water vapor. Water vapor is the only major atmospheric component in which the relative concentration changes with altitude (height above Earth s surface); in general, as altitude increases, water vapor concentration decreases. The atmosphere also includes dust particles, liquid water droplets, and ice crystals. Composition of Earth s Atmosphere Gas Nitrogen % Oxygen % Argon % Carbon Dioxide % Neon % Helium % Methane % Krypton % Hydrogen % Percent of Dry Atmosphere by Volume Water Vapor Highly variable; typically makes up about 1% Source: NASA: E Chemistry Sciences: C. Atmospheric Properties 4

5 Key Vocabulary Solids The molecules in solids are bound tightly and do not move much. This is why solids maintain their shape and volume. Example: Rock Liquids The molecules in liquids are loosely bound and are in motion. Because its molecules are loosely bound, a liquid will take the shape of the container in which it is placed. Example: Water Gases The molecules in gases are not bound to one another. Because of this, a gas does not have a fixed shape or volume. It will expand to fill any container in which it is placed. Example: Air Plasmas Plasma is like a gas in that it spreads out to fill the space that contains it. But plasma is composed of ions (atoms with a negative or positive charge) and free-moving electrons. As a result, plasma conducts electricity. It is a high energy, high temperature state of matter that emits light. Examples: Neon signs, fluorescent lightbulbs, lightning Fluids Fluids are substances that flow freely and tend to assume the shape of the container in which they are held. Liquids, gases, and plasma are considered fluids. Elements Substances made of only one type of atom. Example: Oxygen (O 2 ) Compounds Substances made of two or more types of atoms. Example: Water (H 2 O) Atoms An atom is the smallest particle of an element that retains all the properties of that element. Molecules A particle made of two or more atoms that are chemically bonded. Mass The amount of matter in an object. Weight The pull of gravity on an object or substance. It is proportional to the mass. The greater the mass, the greater the weight. Density The amount of mass per unit volume. Something that is more tightly packed is more dense than something that has more space between the molecules. Volume The amount of space an object occupies. Density of air Mass per unit volume of Earth s atmosphere. Atmospheric pressure The force exerted by air on a unit area. Equilibrium A state of rest or balance due to the equal action of opposing forces. Experimental Design A study used to test causeand-effect relationships between variables. The classic experimental design specifies an experimental group and a control group. Control A procedure identical to the experimental procedure except for the one factor being studied. Independent variable A variable that is manipulated by the researcher and evaluated by its measurable effect on the dependent variable or variables. It is purposely changed so that the effect can be tested. Dependent variable A factor that is measured to learn the effect of one or more independent variables. It is what happens as a result of the independent variable. E Chemistry Sciences: C. Atmospheric Properties 5

6 Density, Volume, and Atmospheric Pressure The density of air is the mass per unit of volume of Earth s atmosphere, and it is a useful value in aeronautics and other sciences. Air density decreases with increasing altitude, and so does air pressure. Density also decreases with increasing temperature or humidity. As the density of air decreases, the volume of a given mass of air will increase. For example, New Orleans is at sea level and has an air density of approximately 1.2 kg/m 3. Denver is at a higher elevation (approximately 5,280 feet above sea level), and it has an air density of approximately 1.05 kg/m 3. Atmospheric pressure is the force exerted by air on a unit area. It can be thought of as the weight of the air against a surface. That is, the fewer molecules above you, the lower the pressure exterted on you and vice versa. (More molecules above you means that the air will exert more pressure on you.) Since there are fewer molecules above you as you move up in the atmosphere, pressure always decreases with increasing altitude. At sea level, the amount of air pressure pushing in all directions is approximately 14.7 pounds per square inch. In Denver, at 5,280 feet, the atmospheric pressure drops to lbs/in 2. ( altitude/index.cfm ) In the United States, pressure is commonly expressed in millibars (mb) or inches of mercury (in. Hg). Meteorologists use millibars (the unit shown on weather maps), and aviation and television weather reports often use inches of mercury. Atmospheric pressure is measured with a barometer, which is why it is sometimes called barometric pressure. The average sea level pressure is mb or in. Hg. 1 mb = in. Hg. How thick is Earth s atmosphere? The term thickness often refers to the density of an atmosphere. Earth s atmosphere is said to be thicker than the Moon s because it is denser. At the surface, Earth s atmosphere contains about particles per cubic centimeter, while the Moon s atmosphere contains on the order of 2 x 10 5 particles per cubic centimeter. The density of the atmosphere decreases exponentially with distance from Earth s surface. Where does Earth s atmosphere end? Because the atmosphere is made of gas, it is hard to say exactly where it ends. Its density decreases gradually with altitude. While some references state that the atmosphere ends at 160 km (100 miles) above sea level, others state that it reaches 560 km (348 miles) or higher. This discrepancy arises becauses most of the E Chemistry Sciences: C. Atmospheric Properties 6

7 mass of the atmosphere is located within the region 75 km (50 miles) above Earth s surface, but some atmospheric gases extend much farther out. For example, the Hubble Space Telescope (HST) orbits Earth at an altitude of about 600 km (374 miles). There are still enough molecules at this altitude that they gradually slow HST down and cause it to lose altitude. There are four layers of the atmosphere: troposphere, stratosphere, mesosphere, and thermosphere. The troposphere is the lowest, densest layer. The troposphere extends to an altitude of about 15 km (9 miles). This height can vary by location and season. Nearly all weather occurs in the troposphere (some weather extends into the lower stratosphere). Most planes fly in the troposphere. The stratosphere is the second layer from the ground. This layer contains most of the ozone that absorbs harmful UV radiation. This absorption causes the stratosphere to be warmer than the top of the troposphere. Where do the gases in Earth s atmosphere come from? Earth s atmosphere has evolved over the 4.6 billion years of Earth s history. The gases that make up Earth s atmosphere come from three main sources: 1. Earth s interior (via volcanic eruptions and radioactive decay) 2. Living things (via biological processes such as photosynthessis and respiration) 3. Outer space (via comets) Why doesn t Earth s atmosphere float away? The atmosphere is made of gases, which means that the atoms and molecules can float freely and are not bonded to each other. Gravity keeps these particles from floating out into space. If Earth s gravity were weaker, there would be fewer particles in the atmosphere. If it were stronger, Earth s atmosphere would be thicker. By comparison, the mass of the moon is small, which means that its gravitational pull is too weak to keep gases from flying out into space. E Chemistry Sciences: C. Atmospheric Properties 7

8 Lesson Note: Refer back to previous lessons on atoms, molecules, elements, and compounds. Introduction: What is the Ocean of Air? Using a globe as a model of Earth, point out the geographic features of Earth, such as landforms and water, and relate them to the states of matter. (Landforms are solids, water is a liquid.) Ask: Are there any other critical features of Earth that are not displayed by the globe model? (The atmosphere) Explain: Atmosphere is the word used to refer to the blanket of gases that surrounds Earth. Even though we cannot see air we know that air particles are all around us because they have particular characteristics that we can observe and measure. Air is a mixture of many different gases. There are mainly two kinds of gas molecules that make up Earth s atmosphere: nitrogen and oxygen. Nitrogen molecules are the most abundant. One reason for this is that nitrogen does not easily react with most substances on Earth. Also, nitrogen is stable in the presence of solar radiation in the atmosphere. Second in abundance are oxygen molecules, most of which are generated through photosynthesis. The remaining part of the atmospheric particles are a mixture of water molecules (water in its gaseous form) and trace amounts of other gases. E Chemistry Sciences: C. Atmospheric Properties 8

9 Activity Give each pair of students a prepared Ziploc bag containing 100 small beads or marbles and a tray or paper plate on which to work. Explain that each bag represents a model of an air sample. Working in pairs, have students separate and count the number of items of each color and enter the numbers into a table to determine the percentage of each gas in the atmosphere. Note: This table is included in the Student Activity Log. Item Nitrogenblue Number of Particles per 100 Fractional Equivalent Decimal Equivalent Percentage of Gases in the Atmosphere 78 78/ % Oxygen - red 21 21/ % Water vapor and other gases - white 1 1/ % Using the information in the chart, have students label the pie-graph in their Activity Logs. The pie-graph represents the percentage of gases in Earth s atmosphere. Explain that closer to the surface of Earth there are more air molecules, but as you move higher in altitude, there are fewer and fewer molecules. The molecules above push down on the molecules below. Therefore, the air close to the surface of Earth is more tightly packed together. The higher in elevation you go, the more the molecules are spread out. E Chemistry Sciences: C. Atmospheric Properties 9

10 Note: If this concept needs further clarification, you can use two objects of the same size and shape, such as a brick and a sponge, to demonstrate that objects with the same volume can have different masses. Note: For a standard globe, the atmospheric thickness is about 0.6 mm, so you will need to use very thin bubble wrap. Several sheets of plastic wrap layered together can also be used. If your globe is larger, you will need to determine what you will need. The amount of space a given amount of material takes up is its volume. The amount of mass per unit of volume is its density. For example, sand is denser than water. Therefore, if you filled one container with water and an identical container with the same volume of sand, the container filled with sand would have a larger mass than the container filled with water. The density of air decreases (the molecules are spread further apart) as you move higher in elevation. Have students observe the altitude density image on their Activity Logs. Then have students fill in the blank areas next to this image in their logs. Demonstration: Blow up and tie off a balloon. Measure and record its circumference in a place visible to the class. Tell the class that you have measured the balloon to see how much space the air molecules are taking up. Tell the class that air molecules will spread apart when the temperature of the air increases. Ask: How can we prove or disprove the idea that the air molecules spread further apart when the air is warmer? Possible answer: We can warm up or cool down the balloon to see if there is any change in the volume of the balloon. Lead students to suggest placing the balloon in the refrigerator for some time. Place the balloon in the refrigerator while you conduct other investigations and remove it later. Height of the Atmosphere: Explain that the atmosphere does not come to an abrupt end but the particles gradually get further and further apart, until there is no significant number left. In some places, the atmosphere extends higher than it does in other places. Because it is a gas and is always in motion and changing shape, you cannot take an exact measurement. However, the average height of the atmosphere is 100 miles. Using the globe model, lay a sheet of thin bubble wrap over the surface, and explain that at this scale, the atmosphere would be about as thick as the bubble wrap compared to the size of the globe. Have students complete this information in their Activity Log. E Chemistry Sciences: C. Atmospheric Properties 10

11 4 Check for Understanding: Before moving on to the investigation of the properties of air, ask students to briefly review the information they just covered concerning the atmosphere. Ask them to select a bit of information and explain it to a partner. On cue, have one partner share what they learned for seconds while the other student listens. At the signal, have students reverse roles, allowing the second partner to share. Circulate and listen to the discussion to determine understanding. Close the discussion by clarifying content as needed. Note: The following activities can be managed through guided, whole group hands-on investigations in pairs or teams of four, or they can be managed through small group rotations through investigation stations utilizing task cards, followed by whole-group debriefs. What are the Properties of Air? Explain to students that scientists have investigated air and have found it to respond in predictable ways. These observable and measureable aspects of air are referred to as its properties. The students will conduct a number of investigations in order to discover some of the properties of air. Property One: Air Takes up Space (Volume) Hold the tornado tube in front of students. Make sure the bottle with water is on the bottom. (Or, if students are investigating in small groups, make sure that the bottle is set up at a station with the water on the bottom.) Ask: What is inside these two bottles? (Air is inside one of the bottles. Water is inside the other bottle.) Ask: What will happen if I invert the bottle? (Relate this term to mathematics and fractions.) Allow students to discuss with their partner. Invert the bottles. Students should observe that the water remains on top. Ask: Why is the water staying in the top bottle? What do you think I need to do to make the water fall through? Ask the students to give suggestions on how to get the water and air to exchange places. Give them time to investigate and try out their ideas on one of the tornado tubes. E Chemistry Sciences: C. Atmospheric Properties 11

12 Strategic Questions: What makes the water move to the bottom bottle? (Gravity pulls the water through the small opening.) Have students observe where the water is moving. (The water is moving along the sides of the bottle.) Why is the water moving down the sides and not down the middle of the opening? (Because the air molecules are moving up the center of the hole and both materials cannot occupy the same space at the same time.) Strategic Questions: On Earth, we have gravity pulling down on everything. If there were no gravity, would we still have mass? Yes, we would still have mass. Without gravity, would we still have weight? No, we would not have weight. After the students investigate, demonstrate by grasping the apparatus (the bottle filled with water on top) and move it in a circular motion until a vortex or funnel forms. The spinning action forces the water away from the center of the coupler, allowing a small funnel to form. Through the vortex, the air moves to the top bottle, making room for the water to come down into the bottom bottle. 4 Check for Understanding: Have students verbalize the generalization that air molecules take up space air has volume. Have students complete corresponding information in their Activity Logs. Property Two: Air Has Mass and Weight Ask: Pose the question, We know that air has mass because it is made of matter and all matter has mass. We have already discovered that air takes up space, or volume, but do you think air has weight? Why or why not? Have student share their thoughts and their rationale with their partner for 60 seconds. Experimental Design Explain that scientists must develop experiments that will test their hypotheses. Tell students that they can use a scale to measure the weight of objects. This is a measure of how much gravity is pulling down on an object. We also need to have something to hold the air molecules in place so we can weigh them. We will use a bottle to capture the air molecules. Show the materials they have available to use for this investigation - a bottle, pressurizing bottle top, and digital scale. Tell them they must develop an investigation using these materials to determine if air has weight. Make sure they understand that the scale is used to measure the weight as gravity pulls down on the mass. The pressuring bottle top pushes more air molecules into the bottle. Give groups 2-3 minutes to agree on a design for the experiment. Circulate to each group and ask leading questions to E Chemistry Sciences: C. Atmospheric Properties 12

13 Note: A spring scale (like a bathroom scale) measures the amount of force required to hold up an object against the force of gravity. When an object is at rest on a scale, the upward force that the scale exerts on the object equals the downward force of gravity on that object. This is how a scale measures the weight of the object. Leading Questions: What is your plan? When you put the bottle on the scale, what are you weighing? How will you know how much of the weight is from the bottle cap and how much, if any, is from the air? What is the minimum number of times you would have to weigh the bottle? Strategic Questions: How could we determine how much more the added air mass weighed? (In math, you subtract to determine the difference, so we could subtract the beginning weight measurement from the ending weight.) assist groups in designing their experiment. Make sure that students think of a hypothesis. For example: If I pump more air into the bottle, it will weigh more. Solicit ideas from various groups and lead them to realize that the bottle must be weighed twice, once without added air and once with added air pumped in. Have students open and close the bottle pumper to make sure that it has not been pressurized. Tell them, We want to make sure we all have approximately the same amount of air in the bottle when we begin our experiment. The students weigh the bottle without added air and record the data in their Activity Log in a table. (Be sure they record the beginning weight in the appropriate blank.) Explain to the students that they are going to put as many air particles in the bottle as they can by pumping the bottle top. The students will take turns pumping air into the bottle by rotating the bottle around the table to each student, changing every 15 seconds on cue. The students will weigh the bottle a second time and record the data. Weight of Bottle and Air Ending weight Beginning weight Difference. _ g. _ g. _ g Ask: What happened the second time? (The weight measurement increased as we pumped in more air.) 4 Check for Understanding: Confirm with each group that the bottle weighed more the second time because of the added air. Ask Does this prove that air has weight? E Chemistry Sciences: C. Atmospheric Properties 13

14 Have students recall their initial hypotheses. Students should state if their findings supported or did not support their hypothesis. Make sure to discuss that disproving initial thoughts is just as important as finding out that you were correct! Property Three: Air Exerts Pressure in All Directions Note: You can use a drilled bowling ball that measures 14.7 lbs or an equivalent object that is 14.7 lbs (such as a sack of flour). Strategic Questions: What does it demonstrate if the measurement is the same after you pump the bottle with more air? (That air does not have weight.) What does it demonstrate if the measurement changes after you pump the bottle with more air? (That air has weight.) Why must we conduct this investigation more than once? (To confirm the results are valid.) Explain that air pushes with 14.7 lbs of pressure per square inch in all directions at sea level. Put a bowling ball on the table and let it bang down. Draw a square inch on the table top with a washable overhead marker and tell them that air is pushing with the weight of that bowling ball on just this one little square. Now imagine if we could place the weight of the bowling ball on each of the one inch squares. That would mean that every square inch would be covered on this table top with bowling balls, with all of their weight pushing down on the table top. That s what air is actually doing to the table; pushing down on the table top with the weight of a bowling ball on every square inch! Ask: Why doesn t the table collapse from all of the pounds of pressure pushing on it? Point out that although the table legs are very strong, they could not support that many bowling balls. Lead the students to realize that air is not only pushing down from above, but also up from below and side to side. There is equal pressure on all sides. Have the students hold out their hand, palm up. Have them place their other hand on top, palm down. Tell them to push down with one hand and up with the other with equal force. No matter how hard they push, if the force is equal, nothing moves. This balance of forces is referred to as equilibrium. Have the students think about how air is pushing on the outside of their bodies in the same way. Draw a square inch on your arm and have them imagine all the bowling balls pushing in on their bodies. Ask: Why are we not crushed by the force? Guide the discussion for the students to understand that air is exerting pressure on everything it touches. Not only is there air outside our bodies pushing in, but there is air and other fluids inside our bodies pushing out with equal force. If there were no pressure inside our body, the pressure of the outside would crush us. E Chemistry Sciences: C. Atmospheric Properties 14

15 Ask: There is little or no atmosphere in space. What do you think would happen if an astronaut went out into space without a pressurized space suit to protect his or her body? Note: Although not as dramatic as the bell jar, this activity can be conducted using mini-marshmallows and syringes without the bell jar. The students place the marshmallow inside the syringe, place their finger over the hole in the end and pull the plunger back slightly. This expands the volume inside the syringe, causing the air molecules the spread out. This decreases the air pressure inside the syringe, causing the marshmallow to expand. When the plunger is pushed back in, the marshmallow will shrink. Strategic Questions: Do you think that air pressure is the same everywhere? Why or Why not? What do you think may cause air pressure to change? (Elevation, vacuums, compressed air streams, heating and cooling of molecules) Explain that there would be air and fluids inside the astronaut s body pushing outward, but since there is little atmosphere in space, there would not be any air pushing inward on the body. This would cause the astronaut s body to explode. Provide each pair of students with a bell jar with tubing, a syringe, and a marshmallow. Show the students that they will place the marshmallow inside the bell jar. Insert the tube into the bell jar and attach the syringe to the tube. Explain that the marshmallow represents the astronaut and the bell jar represents space. Have the students pull back on the syringe. This will draw air out of the jar. When air is removed from the bell jar (simulating conditions in space), the fluid inside the marshmallow continues to press outward (simulating the fluid pressure inside our bodies). As air is removed from the jar, the marshmallow will expand. Demonstrate that the bell jar cannot be lifted. Ask the students why. (The air on the outside of the jar is pushing in on all sides but there is no air on the inside to press outward. This creates an unbalanced force acting inward on the bell jar.) Allow them to predict what will happen when they allow the air to flow back in. Have the students twist the connector on the top to return the air into the bell jar. The marshmallow will shrink, and they will once again be able to open the jar. Have the students observe results and discuss. Revisit the investigation of the balloon in the refrigerator. Have a volunteer measure and record the circumference of the balloon. The students should see that the circumference of the balloon has decreased because the colder air (after refrigeration) takes up less space than the warmer air did. Ask: Which do you think exerts more pressure, warm air or cold air? Why? (In warm air, the molecules are farther apart. Therefore, they will probably exert less pressure.) Ask: How do you think differences in air pressure relates to wind flow? (The wind will flow from areas of higher pressure to lower pressure.) Ask: What do you think would happen to you if you went to a planet that has a much denser atmosphere than Earth? (You might be crushed.) E Chemistry Sciences: C. Atmospheric Properties 15

16 This is one of the reasons why an astronaut must wear a spacesuit in space. The absence of air pressure on the outside would allow the fluid on the inside to expand, causing the astronaut s body to explode. 4 Check for Understanding: Have students complete the information about air pressure in their Activity Logs. Air Is a Fluid Refer back to the globe model of Earth. Have students identify the solid matter on the globe (landforms), the liquid matter on the globe (oceans, lake, rivers) and the invisible gases (the atmosphere). Remind them that solids, liquids, and gases are three of the states of matter previously studied. Ask students if they are familiar with the subcategory of matter, fluids. Tell them that we are going to conduct a test to determine whether solids, liquids, or gases also belong in the subcategory of fluids. Allow them to discuss with their partners whether or not they think each of these states of matter is a fluid. Explain that by definition, a fluid easily changes its shape. The molecules will separate so you should be able to put your hand (or another object) into a fluid. A fluid can also be poured. To demonstrate, carry out the following: Pick up a solid object such as a rock. Ask: Does this object have a definite shape? Is it keeping its shape? (Yes) Can I put my hand in it? (No) Can I pour it? (No) Using a table, have students determine with this test that a solid is not a fluid (See sample table). What is a FLUID? A fluid: does not have its own shape separates and flows can be poured Is a solid a fluid? YES NO Is a liquid a fluid? YES NO Is a gas a fluid? YES NO E Chemistry Sciences: C. Atmospheric Properties 16

17 With an aquarium of water and a flask, repeat the three tests with a liquid. Using the table, have students determine with this test that a liquid is a fluid. Using the same aquarium and two flasks, repeat the three tests with a gas (air). When determining if a gas can be poured, push one flask into the aquarium right side up, allowing it to fill with water, and turn the other flask upside down, keeping it full of air. Carefully pour the air under the water from one flask into the other. The students can observe the bubbles of air entering the flask. Using a table, have the students determine with this test that a gas is a fluid. Therefore, the gases in the atmosphere have fluid properties. Conclusion: Understanding about the air is important in many scientific investigations and will be important in helping us in understanding aeronautics. Air is made up of mainly three types of gas molecules: 78% nitrogen, 21% oxygen, and 1% of trace gases. Air that is closer to the surface of Earth is denser and exerts more pressure on objects. Air takes up space. The volume increases as air becomes warmer. Air has mass and weight. Air exerts pressure in all directions. Pressure decreases with altitude. Air is a fluid. E Chemistry Sciences: C. Atmospheric Properties 17

18 Fluid Investigations Activity Activity Log Ocean of Air The atmosphere is the blanket of that surrounds Earth. It is made up of particles so small you can t see them around you. They are held in place by. The Gases in the Atmosphere Type of Gas Number of Particles per 100 Equivalent Fraction Decimal Equivalent Percentage of Gases in the Atmosphere Nitrogen (Blue) % Oxygen (Red) % Water Vapor and Trace Gases (White) % Elevation and Air Density Farther from the surface of Earth, the air is dense. Increasing Altitude Closer to the surface of Earth, the air is dense. ATMOSPHERE About miles thick. E Chemistry Sciences: C. Atmospheric Properties 18

19 Fluid Investigations Activity Activity Log The Properties of Air Experiment #1: Air molecules have. Air molecules take up. Experiment #2: Air molecules have. What is the force of gravity acting downward on an object? Weight of Bottle and Air Ending weight. g Beginning weight. g Difference. g Experiment #3: Air molecules exert in all directions. When air is taken OUT of the jar, the marshmallow. When air is put back IN the jar, the marshmallow. What is a FLUID? A fluid: does not have its own shape separates and flows can be poured Is a solid a fluid? YES NO Is a liquid a fluid? YES NO Is a gas a fluid? YES NO This shows us that. E Chemistry Sciences: C. Atmospheric Properties 19

20 Fluid Investigations Activity Key Activity Log The Properties of Air Experiment #1: Tornado Tube Air molecules have volume. Air molecules take up space. Experiment #2: Mass and Weight Air molecules have mass. What is the force of gravity acting downward on an object? weight Weight of Bottle and Air Ending weight. g Beginning weight. g Difference. g Experiment #3: Marshmallow in bell jar Air molecules exert pressure in all directions. When air is taken OUT of the jar, the marshmallow expands. When air is put back IN the jar, the marshmallow returns to its original size. What is a FLUID? A fluid: does not have its own shape separates and flows can be poured Is a solid a fluid? YES NO Is a liquid a fluid? YES NO Is a gas a fluid? YES NO This shows us that air is a fluid. E Chemistry Sciences: C. Atmospheric Properties 20

21 Fluid Investigations Activity Key Activity Log Ocean of Air The atmosphere is the blanket of gases that surrounds Earth. It is made up of particles so small you can t see them around you. They are held in place by gravity. The Gases in the Atmosphere Type of Gas Number of Particles per 100 Equivalent Fraction Decimal Equivalent Percentage of Gases in the Atmosphere Oxygen Traces of gases Nitrogen (Blue) % Oxygen (Red) % Water Vapor and Trace Gases (White) % Nitrogen Elevation and Air Density Farther from the surface of Earth, the air is less dense. Increasing Altitude Closer to the surface of Earth, the air is more dense. ATMOSPHERE About 100 miles thick. E Chemistry Sciences: C. Atmospheric Properties 21

22 Fluid Investigations Assessment Suggested Final Assessment Questions 1. What are the major components of the atmosphere? What percentage of each is found under ordinary conditions? 2. In which city would the air be more dense, New Orleans at sea level, or Denver, the Mile High City? (1 mile = 5,280 ft.) Which city would have higher atmospheric pressure? Explain your answer. 3. What is the difference between weight and mass? 4. How is the atmosphere similar to the ocean? E Chemistry Sciences: C. Atmospheric Properties 22

23 Fluid Investigations Assessment Key Suggested Final Assessment Questions Knowledge 1. What are the major components of the atmosphere? What percentage of each is found under ordinary conditions? Possible answer: nitrogen 78%, oxygen 21%, water vapor mixed with other gases and particulate matter 1%. Application Analysis Synthesis 2. In which city would the air be more dense, New Orleans at sea level, or Denver, the Mile High City? (1 mile = 5,280 ft.) Which city would have higher atmospheric pressure? Explain your answer. Possible answer: The air in New Orleans would be more dense and have more pressure because there would be many more air molecules above you, pushing molecules together. Denver is higher in elevation, and there would be less air on top pushing down, so the molecules would be able to spread further apart. Therefore, it would also have less pressure. 3. What is the difference between weight and mass? Possible answer: Mass is the amount of matter in an object. Weight is the force of gravity pulling on a object. If you have more mass, there are more molecules for gravity to pull on, so you have more weight. 4. How is the atmosphere similar to the ocean? Possible answer: The ocean and the air are both large bodies of fluids that wrap around everything they touch. They both have volume, mass, weight, and pressure. Neither the ocean nor the air has a definite shape (their shapes continually change). The molecules in the atmosphere and ocean separate and flow, and both can be poured. E Chemistry Sciences: C. Atmospheric Properties 23

24 Sources Kids Discover: Matter. Volume 18, Issue 10, Oct E Chemistry Sciences: C. Atmospheric Properties 24