lesson 28: antigravity water

342LESSON 1: Goofy Putty 342LESSON 1: Goofy PuttyYou Be The Chemist Activity Guides | page 342You Be The Chemist Activity Guides | page 342You Be The Chemist Activity Guides | page 342You Be The Chemist® Activity Guide | page 342

LESSON 28: Antigravity WaterESTIMATED TIME Setup: 5 minutes | Procedure: 5–10 minutes

• DESCRIPTIONFlip a cup of water upside down to demonstrate theeffects of attractive forces and air pressure.

• OBJECTIVEThis experiment demonstrates the effects of pressureand attractive forces. Students observe as these forceswork together to keep water inside an inverted cup.The lesson can also be extended to discuss the polarityof water molecules.

• CONTENT TOPICSScientific inquiry; states of matter; properties of matter;force (pressure); attractive forces (surface tension,adhesion, cohesion)

• MATERIALSo Clear plastic cups (high strength) or glass cups

o Large bowl or dish (to catch falling water) o Index cards (large enough to cover the rim of

the cup) o Mason jar or similar jar with a screw-on top

(optional)

Always remember to use the appropriate safetyequipment when conducting your experiment.

Refer to the Safety First section in the Resource Guideon pages 421–423 for more detailed information aboutsafety in the classroom.

Jump ahead to page 345 to view theExperimental Procedure.

OBSERVATION & RESEARCH

BACKGROUNDScientists use the term “matter” to describe the thingsaround you. Matter is anything that has mass and takes upspace, such as paper, food, skin, and water. Matter primarilyexists in three states on the earth—solid, liquid, or gas.Solids have a definite volume and a definite shape.Examples of solids are chairs, books, and cups. Liquids havea definite volume but no definite shape. Examples of liquidsare water and orange juice. Gases have no definite shapeand no definite volume. An example of a gas is the airaround you! In addition to differences in shape and volume,solids, liquids, and gases have other unique properties.

Particles in a liquid move around freely, but stillexperience forces of attraction. Cohesion is the attractive

force that exists between like particles in a liquid. Watermolecules are strongly attracted to one another. Surfacetension is another property of liquids that results fromcohesion. The strong attraction of particles at the surface ofthe liquid creates a surface “film” that makes moving anobject through the surface of a liquid more difficult thanmoving the object when it is completely submerged in theliquid. Conversely, adhesion is the force of attractionbetween unlike molecules. It’s the force that causes watermolecules to stick to the inside of a glass or an index card.

In the experiment, the water molecules in the cup sticktogether because of cohesion. The water molecules alsostick to the sides of the cup and index card because ofadhesion. These attractive forces pull all the water

NATIONAL SCIENCE EDUCATION STANDARDS SUBJECT MATTERThis lesson applies both Dimension 1: Scientific and Engineering Practices and Dimension 2: Crosscutting Conceptsfrom “A Framework for K–12 Science Education,” established as a guide for the updated National Science EducationStandards. In addition, this lesson covers the following Disciplinary Core Ideas from that framework: • PS1.A: Structure and Properties of Matter • PS2.A: Forces and Motion • PS2.B: Types of Interactions • ETS2.A: Interdependence of Science, Engineering, and Technology (see Analysis & Conclusion)

FORMULAS & EQUATIONSTap water is a mixture of pure water and dissolvedminerals.

The chemical formula for pure water is H2O.

This formula illustrates that a molecule of water iscomprised of two hydrogen atoms and one oxygen atom.

Air is a mixture of gases. The air around us is made upmainly of nitrogen and oxygen gas.

The chemical formula for nitrogen gas is N2.

The chemical formula for oxygen gas is O2.

Approximately 78% of the air is N2, and about 21% is O2.The remaining 1% is made up of trace gases, such as argon(Ar), carbon dioxide (CO2), water vapor (H2O), and othergases.

Pressure is the amount of force exerted on an area. Thisrelationship is described by the following equation:

p = F/A

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LESSON 28: Antigravity Watermolecules in the cup tightly together. In addition, whenthe index card is held to the rim of the inverted cup, thetightly held water molecules along the rim of the cup andwalls of the cup form a “film” or seal around the rim ofthe cup. This seal prevents air from entering the cup anddisplacing the water. Displacement is the act of movingsomething out of its original position or of one substancetaking the place of another. The seal isn’t perfect, andthere is a slight gap between the cup and index card.However, this gap is too small for air to break the surfacetension of the water molecules.

In addition, the particles that make up a gas (the air) movearound freely in rapid random motion. They do not havestrong bonds or attractions between them. The air particlesbounce around and collide with one another, creatingpressure. Pressure is the amount of force exerted on anarea. Air pressure, or atmospheric pressure, is the forceexerted on a surface by the weight of the air above thatsurface.Yet because the particles move in all directions,air pressure is exerted from all angles, not just down. The average air pressure at sea level is about 14.7pounds per square inch (101.325 kPa). That’s almost 15 pounds of air pushing on every inch of our bodies!

Likewise, air pressure is pushing on the cup from alldirections. If the cup is full of water, there is essentially noair pressure in the cup. While the force of gravity is pullingdown on the water, the attractive forces of the water andthe air pressure are pushing up and holding the index cardin place. The greater exertion of these forces keeps theindex card sealed to the cup. If the cup is about half tothree-quarters full, air and water are inside the cup. Whenthe cup is inverted, a little water will drip out of the cup.With less water, the air pocket in the cup increases. The gasparticles will spread out to fill the extra space in the cup,causing the pressure inside the cup to decrease. Therefore,the air pressure outside of the cup is greater than thepressure inside, again exerting a greater upward force.

HYPOTHESIS

uWater will remain in an inverted cup

with only an index card covering the opening

because of air pressure and the forces of attraction

experienced by the water molecules.

CONNECT TO THE YOU BE THECHEMIST CHALLENGE

For additional background information, please

review CEF’s Challenge study materials online at

http://www.chemed.org/ybtc/challenge/study.aspx.

• Additional information on states and properties ofmatter can be found in the Classification of Mattersection of CEF’s Passport to Science Exploration:The Core of Chemistry.

• Additional information on pressure can be foundin the Measurement section of CEF’s Passport toScience Exploration: The Core of Chemistry.

http://www.chemed.org/ybtc/challenge/study.aspx


LESSON 28: Antigravity Water

LOWER GRADE LEVELS/BEGINNERSConduct the experiment as described on page 345, butspend more time on the states and properties of matter.Show images of matter in different states, and havestudents identify the state of matter.

Likewise, you can discuss the concept of pressure in moredetail. If the students move around the room like gasparticles, will they feel more pressure if more studentsenter the room? If there were less students in the room,will it be easier to move around without bumping intoanyone? Use this example to discuss why the pressure inthe cup decreases when some of the water escapes fromthe glass.

HIGHER GRADE LEVELS/ADVANCED STUDENTSDESCRIPTIONFlip a cup of water upside down to demonstrate theeffects of attractive forces and air pressure.

OBJECTIVEThis experiment demonstrates how air pressure andattractive forces, including the polarity of water molecules,work together to keep water inside an inverted cup.

OBSERVATION & RESEARCHMatter exists primarily in three states on the earth—solid,liquid, or gas. The difference between solids, liquids, andgases is in the motion of the particles within thesubstance. For example, the molecules of H2O movedifferently in the form of ice than they do in the form ofwater vapor.

The particles in a solid are generally locked into place by strong attractive forces giving the solid substance adefinite shape and volume. Particles in a liquid are not asclose as particles in a solid, and they move more freely.The particles roll over each other but still experienceweak forces of attraction. The particles in a gas arespaced far apart. They do not have strong bonds orattractions between them. Therefore, they move aboutfreely and rapidly in random directions.

Cohesion is the attractive force that exists between likeparticles in a liquid. (It’s the attraction that causes likemolecules to stick together.) Water molecules arestrongly attracted to one another. They are polarmolecules. Polar substances are made up of particles that have an uneven distribution of electrons, creating anegative and a positive side. The oxygen atom in a watermolecule has a partial negative charge, and the hydrogenatoms have partial positive charges. Because “oppositesattract,” the negatively charged oxygen atom attracts thepositively charged hydrogen atoms in other water

molecules. When the molecules interact, they form stronghydrogen bonds.

Surface tension is another property of liquids that resultsfrom cohesion. The strong attraction (cohesion) ofparticles at the surface of the liquid creates a surface“film” that makes moving an object through the surfaceof a liquid more difficult than moving the object when itis completely submerged in the liquid. Conversely,adhesion is the force of attraction between unlikemolecules. It’s the force that causes water molecules to stick to the inside of a glass or an index card.

In the experiment, the water molecules stick to the cupand each other because of adhesion and cohesion. Whenthe index card is held to the rim of the inverted cup, thetightly held water molecules along the rim of the cup andwalls of the cup form a “film” or seal around the rim. Theseal prevents air from entering the cup and displacing thewater. The seal isn’t perfect, and there is a slight gapbetween the cup and the index card. However, this gap istoo small for air to break the water’s surface tension.

In addition, air particles bounce around and collide withone another, creating pressure. Pressure is the amount offorce exerted on an area. Air pressure, or atmosphericpressure, is the force exerted on a surface by the weightof the air above that surface. However, because theparticles move in all directions, air pressure pushes on thecup from all directions. If the cup is full of water, there is

CONNECT TO THE YOU BE THECHEMIST CHALLENGE

For additional background information, pleasereview CEF’s Challenge study materials online athttp://www.chemed.org/ybtc/challenge/study.aspx.

• Additional information on states and properties ofmatter can be found in the Classification of Mattersection of CEF’s Passport to Science Exploration:The Core of Chemistry.

• Additional information on pressure can be found inthe Measurement section of CEF’s Passport toScience Exploration: The Core of Chemistry.

• Additional information on polarity can be found inthe Chemicals by Volume—Solutions section ofCEF’s Passport to Science Exploration: ChemistryConnections.

DIFFERENTIATION IN THE CLASSROOM

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LESSON 28: Antigravity Water

EXPERIMENTATION

As the students perform the experiment, challenge them to identify the independent, dependent, and controlled variables,

as well as whether there is a control setup for the experiment. (Hint: If the index card is moved, will water stay in the

cup?) Review the information in the Scientific Inquiry section on pages 14–16 to discuss variables.

EXPERIMENTAL PROCEDURE

1. Fill a cup with water at least halfway.

2. While the cup is still right-side up, place the index

card over the rim. (Wet the rim slightly, and be sure

the index card covers the entire opening of the cup.)

3. While holding the index card in place, carefully

invert the cup.

4. Let the water settle for a second, make sure the

card is touching all the way around the rim, and

cautiously let go of the card.

DIFFERENTIATION IN THE CLASSROOM

essentially no air pressure in the cup. While the force ofgravity is pulling down on the water, the attractive forcesof the water and the air pressure are pushing up andholding the index card in place. The greater exertion ofthese forces keeps the index card sealed to the cup.

If the cup is about half to three-quarters full, air and waterare inside the cup. When the cup is inverted, a little water

will drip out of the cup. With less water, the air pocket inthe cup increases. The gas particles will spread out to fillthe extra space in the cup, causing the pressure inside thecup to decrease. Therefore, the air pressure outside of thecup is greater than the pressure inside, again exerting agreater upward force.

Make sure the cup is turned completely

upside down so that the index card is

parallel to the ground.

It helps to wet the rim of the cup slightly

before placing the index card on it, so

there are water molecules on the rim to stick to

the index card.

It is best to perform the experiment over

a large bowl or sink.

DATA COLLECTION

Have students record data in their science notebooks or on the following activity sheet. What forces of attraction cause water

molecules to stick to each other and to other substances? What other forces are involved in this activity? Have students

answer the questions on the activity sheet (or similar ones of your own) to guide the process.


LESSON 28: Antigravity WaterANALYSIS & CONCLUSION

Use the questions from the activity sheet or your ownquestions to discuss the experimental data. Ask studentsto determine whether they should accept or reject theirhypotheses. Review the information in the ScientificInquiry section on pages 14–16 to discuss valid andinvalid hypotheses.

ASSESSMENT/GOALSUpon completion of this lesson, students should be ableto …

• Apply a scientific inquiry process and perform anexperiment.

• Differentiate between the different states of matter.

• Describe the attractive forces of adhesion andcohesion.

• Describe surface tension and its relation to cohesion.

• Define and provide examples of pressure and airpressure.

• Explain the polarity of water (see Differentiation inthe Classroom).

MODIFICATIONS/EXTENSIONS

Modifications and extensions provide alternative methodsfor performing the lesson or similar lessons. They alsointroduce ways to expand on the content topics presentedand think beyond those topics. Use the followingexamples, or have a discussion to generate other ideas as a class.

• Take the experiment a step further. Cut out the centerof a jar’s lid, but be sure you can still screw on thelid. Cover the opening of the jar with a piece of thewindow screen just large enough to cover the rim.Then screw the lid on the jar. Perform thisexperiment as a demonstration for the students;however this time, pull the index card slowly awayfrom the inverted jar. The water will not fall out ofthe jar. The strong attraction of the water moleculesto each part of the screen and the high surfacetension of the water prevents the water from fallingthrough the tiny holes. However, this stability is verydelicate; even if you slightly touch the screen, thewater will fall out.

• To illustrate the important role of cohesion and surfacetension to the experiment, add soap or detergent to thewater. Soap and detergents are surfactants and reducethe surface tension of liquids. Watch what happenswhen you try the experiment with soap in the cup.(Make sure you perform this demonstration over asink or large bowl to catch the water!)

• Test other liquids. Water and oil can also be heldinside the cup. However, soda pop and othercarbonated drinks cannot. The carbon dioxide gasdissolved in these beverages exerts extra pressureinside the glass. Therefore, the attractive forces andair pressure outside the cup are not enough to holdthe index card in place.

REAL-WORLD APPLICATIONS

• Generally, when you pour a liquid from a container, airwill take the place of the removed liquid. Therefore,when you drink a bottle of soda pop or juice, the bottledoes not crush inward when some of the liquid isremoved. Air moves into that space to equalize thepressure inside the bottle and outside the bottle.Likewise, gas lawnmowers generally have an air vent.That way, when gasoline is poured into the lawnmower, the air that was filling the space has a place toescape. Otherwise, the gasoline will splash all over asair from inside tries to rush out of the same hole intowhich you are pouring the gasoline.

• If you drink water from a straw, you may notice thata small amount of the liquid remains in the bottom of the straw if you pull the straw out of the liquid.The water stays in the straw without an index card or small piece of paper because the diameter of thestraw is so small that the surface tension of the liquidalone keeps the liquid inside.

COMMUNICATION

Discuss the results as a class and review the activity sheet.Review the information in the Scientific Inquiry section onpages 14–16 to discuss the importance of communicationto scientific progress.

You Be The Chemist Activity Guides | page 347You Be The Chemist® Activity Guide | page 347

LESSON 28 ACTIVITY SHEET: Antigravity Water

OBSERVE & RESEARCH

1. Write down the materials you observe. ________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

2. Predict how these materials may be used. ______________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

3. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an

image of the example.

Term Definition Example (write or add image)

Solid

Liquid

Gas

Cohesion

Surface tension

Adhesion

Displacement

Pressure

Air pressure



4. Consider what will happen to an index card placed over the opening of a cup filled with water when the cup is inverted and why.

uWrite your hypothesis. ______________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________

PERFORM YOUR EXPERIMENT

1. Fill a cup at least halfway with water.

2. While the cup is still right-side up, place an index card over the rim. (Wet the rim slightly, and make sure the card

covers the entire rim of the cup.)

3. While holding the index card in place with your palm, carefully flip the cup upside down. Try to keep the water

from leaking out of the cup. Be careful not to squeeze the cup.

4. Let the water settle for a couple of seconds. Make sure the card is touching all the way around the rim, and then

cautiously let go of the card. Observe what happens.

1. What do you feel when you flip the cup upside down? __________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

2. What happens once you remove your hand from under the inverted cup? ____________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

3. Why do you think this occurs? What forces are present? ________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

ANALYZE & CONCLUDE

You Be The Chemist Activity Guides | page 349You Be The Chemist® Activity Guide | page 349


4. What might happen if you squeeze the sides of the cup? Why? ____________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

5. What do you think will happen if you remove the card while the cup is still upside down? Why? ________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

6. Is your hypothesis valid? Why or why not? If not, what would be your next steps? ____________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________



EXPAND YOUR KNOWLEDGE—ADVANCED

1. Define the following key term. Then, provide an example of it by writing the example or drawing/pasting an image

of the example.


Polar substance

2. Why are water molecules considered polar substances? ________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

3. Would the experiment work with other liquids? Why or why not? ________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________


LESSON 28 ACTIVITY SHEET: Antigravity WaterANSWER KEY: Below are suggested answers. Other answers may also be acceptable.

OBSERVE & RESEARCH

1. Write down the materials you observe. ________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

2. Predict how these materials may be used. ______________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

3. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an

image of the example.


Solid A state of matter characterized by a definite volumeand a definite shape.

LiquidA state of matter that has a definite volume but nodefinite shape; a liquid will take the shape of thecontainer that holds it, filling the bottom first.

GasA state of matter that has no definite volume orshape; a gas will take the shape of the containerthat holds it, filling the entire container.

CohesionAn attractive force that holds atoms or ions of asingle body together; an attraction betweenparticles of the same kind.

Surface tensionA property of liquids that describes the attraction ofliquid particles at the surface; the strong attractionof particles at the surface of a liquid creates asurface “film.”

Adhesion An attractive force that holds atoms or ions ofdifferent substances together.

DisplacementThe act of moving something out of its originalposition or of one substance taking the place ofanother.

Pressure The force exerted on an area; p = F/A

Air pressure The cumulative force exerted on a surface by theweight of the air particles above that surface.

Plastic cups, large bowl, index card …

A plastic cup may be filled with water. A large bowl may be used to hold a large amount

of a substance. An index card may be used to take notes. These materials may be used to demonstrate the effects of pressure and surface

tension.

4. Consider what will happen to an index card placed over the opening of a cup filled with water when the cup is inverted and why.

uWrite your hypothesis. ______________________________________________________________

______________________________________________________________________________________

______________________________________________________________________________________



Water will remain in an inverted cup with only an index card covering the opening

because of air pressure pushing on the card and the attractive forces of water molecules.

PERFORM YOUR EXPERIMENT

1. Fill a cup at least halfway with water.

2. While the cup is still right-side up, place an index card over the rim. (Wet the rim slightly, and make sure the card

covers the entire rim of the cup.)

3. While holding the index card in place with your palm, carefully flip the cup upside down. Try to keep the water

from leaking out of the cup. Be careful not to squeeze the cup.

4. Let the water settle for a couple of seconds. Make sure the card is touching all the way around the rim, and then

cautiously let go of the card. Observe what happens.

1. What do you feel when you flip the cup upside down? __________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

2. What happens once you remove your hand from under the inverted cup? ____________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

3. Why do you think this occurs? What forces are present? ________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

ANALYZE & CONCLUDE

You feel movement of the water inside the cup and the increased

pressure of the water on the index card.

The index card remains attached to the cup, and

the water stays in the cup.

If the cup is completely full of water, there is no air inside the cup.

With no air, and therefore no air pressure inside the cup, the air pressure outside of the cup is greater than the air pressure inside. Therefore,

the air pressure outside of the cup pushes up on the index card, forcing the card and water to stay in place. In addition, the adhesion of water

molecules to the index card and the surface tension of the water molecules hold the index card in place. If the cup is not completely full, some

of the water will leak out when the cup is inverted. As a result, the air pressure inside the cup will decrease, and the air pressure outside will

push up and hold the index card in place.



4. What might happen if you squeeze the sides of the cup? Why? ____________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

5. What do you think will happen if you remove the card while the cup is still upside down? Why? ________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

6. Is your hypothesis valid? Why or why not? If not, what would be your next steps? ____________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

Squeezing the sides of the cup breaks the surface tension of

the water and releases the seal between the card and the cup. As a result, the water pours out.

The water will

pour out of the cup because the card is no longer blocking the air from displacing the water in the cup.

Answer 1: Valid because the data support my hypothesis.

Answer 2: Invalid because the data do not support my hypothesis. I would reject my hypothesis and could form a new one, such as …



EXPAND YOUR KNOWLEDGE—ADVANCEDHave students complete this section if you used the advanced differentiation information, or challenge them to find the answers to these

questions at home and discuss how these terms relate to the experiment in class the next day.

1. Define the following key term. Then, provide an example of it by writing the example or drawing/pasting an image

of the example.


Polar substanceA substance made up of particles that have an unevendistribution of electrons, creating a negative and apositive side.

2. Why are water molecules considered polar substances? ________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

3. Would the experiment work with other liquids? Why or why not? ________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

______________________________________________________________________________________________________

The oxygen atom in a water molecule carries a partial negative

charge, and the hydrogen atoms carry partial negative charges.

Some liquids may behave like water because the

attractive forces in the liquid are similar to those in water. However, other liquids may not work. Carbonated beverages, such as soda pop,

will not stay inside the cup because the dissolved carbon dioxide gas in the liquid exerts extra pressure inside the glass. Therefore, the

attractive forces acting on the liquid and the air pressure outside of the cup are not enough to hold the index card in place.

lesson 28: antigravity water

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