Density and Air Pressure Teacher Kit

Alex BishopDensity and Air Pressure 1/8/14

Density and Air PressureTEACHER’S INSTRUCTIONS

DESCRIPTION: The lesson uses both demos and activities to explain density and air pressure,

including the effect that they have on one another.

LEARNING GOALS:

Students will test-

A) Whether a small object (paper towel ball) can fit into a large object (soda bottle) “filled”

with air

B) Which objects rest where in a density column (ping pong ball, soda cap, bead, popcorn

kernel, nail, ice)

C) How density and carbonation affect whether lemon seeds float or sink (i.e. why lemon

seeds dance)

Students will observe-

A) How the presence or absence of an orange peel affects buoyancy of an orange

B) The formation of a density column (honey, corn syrup, dish soap, vegetable oil, rubbing

alcohol, lamp oil)

C) How air pressure can be used to force a peeled hard-boiled egg into an Erlenmeyer flask

D) How air pressure and surface tension allows a playing card to hold 500 mL of water in

an Erlenmeyer flask held upside down

Students will understand-

A) Air pressure: identity (what air pressure is), strength (compared to pressure at the bottom

of a body of water), and why we do not feel it (constantly exposed to air pressure)

B) Density: concept (comparing two similarly sized objects with different masses)

RECOMMENDED AGE LEVELS: K–8th grade

ESTIMATED TIME REQUIRED: 45 minutes – 1 hour, prep time 30 minutes

KEY CONCEPTS AND DEFINITIONS OF TERMS:

Air Pressure: Force caused by the pressure of air molecules. The force is similar to the force we feel

at the bottom of a body of water. The reason that we are unaware of the force of air pressure is that

air pressure is never released (like water pressure is).

Mass: Amount of matter a substance contains.

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Alex BishopDensity and Air Pressure 1/8/14Matter: Anything that has mass and takes up space, “stuff”.

Volume: Quantity of 3D space occupied by a solid, liquid, or gas.

Density: Mass per unit volume, Objects with density lower than the liquid float (those with a higher

density sink)

MATERIALS:

1. Hardboiled egg (1), large narrow necked glass bottle (ex: 1L Erlenmeyer flask, 1 needed),

birthday candles (2), matches or lighter (1)

2. 21-ounce soda bottles (1 per student), paper towels (~5 per class, small piece per student)

3. Graduated cylinder, honey, corn syrup, dish soap- preferably blue or another distinguishable

color, vegetable oil, rubbing alcohol, lamp oil, food coloring (if desired), ping pong ball,

soda cap, bead, popcorn kernel, nail

4. Orange (1), clear bucket (1), water, two objects of similar size and very different densities

(ex: golf ball and ping pong ball)

5. Clear carbonated drink (ex: seltzer water, 1 liter bottle), lemon seeds (a few per student),

small clear cups (1 per student), 1 large clear plastic cup for demonstration

NOTE: clear carbonated drink and lemon seeds should both be very fresh; I recommend that

you test this demonstration prior to class

6. Playing card (1), Erlenmeyer flask (1), water

SAFETY INFORMATION: Instructors and students should wear safety goggles at all times.

Handle matches or lighter with caution and perform Upside Down Egg in the Bottle at a distance

from students.

GENERAL OUTLINE OF PROCEDURES:

1. Demonstration: Upside Down Egg in the Bottle

A. Peel the hardboiled egg prior to the demonstration.

B. Demonstrate that the egg will not fit inside the Erlenmeyer flask by simply

pushing on it.

C. Show students the egg, the Erlenmeyer flask, birthday candles, and matches. Ask students

to raise their hand if they have seen the trick. If only one or two students have seen the trick,

ask them to assist. If there are more students, ask them to refrain from answering the next

question.

D. Ask how the students how they would suggest getting the egg inside the bottle using just

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Alex BishopDensity and Air Pressure 1/8/14 the two materials (lighter, candles) but without breaking it.

E. Try the suggestions if possible to show that they do not work.

F. Place two birthday candles close together at the skinny end of the egg. Ensure that the

candles will fit inside the neck of the Erlenmeyer flask.

G. Light the birthday candles and hold them in the mouth of the Erlenmeyer flask.

H. After about 10 seconds, move the egg up. The candles will go out and the egg

may start to vibrate.

I. Result: The egg is pushed into the bottle.

J. To remove the egg, tip the Erlenmeyer flask upside down so that the base faces

the ceiling. Take a deep breath and forcefully blow air into the mouth of

the Erlenmeyer flask. Move your face quickly so that the egg does not hit you.

K. How it works: Instead, the air pressure outside the Erlenmeyer flask pushes the egg in.

The egg is not “sucked” or “pulled” into the Erlenmeyer flask.

2. Class Activity: Bet You Can’t

A. Prior to class, roll paper towels into balls (1 per student) about half the size of the neck

of the soda bottle.

B. Have students lay their soda bottle horizontally on the table.

C. Have students place their paper towel ball in the neck of the bottle on the edge (see

below).

D. Ask students to take a deep breath and blow as hard as possible to try to move the paper

towel ball into the soda bottle.

E. Result: No matter how hard you blow, the paper towel ball does not go into the soda

bottle. In fact, it travels back in the opposite direction (towards you).

F. How it works: The soda bottle is already filled with air; there is no room for the excess air

or the paper towel ball. The excess air will flow back, pushing the paper towel ball out.

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Suggested Activity (5 th -8 th grade): Discuss the factors that affect atmospheric pressure: altitude,

water vapor, wind patterns. See this link for how to make a barometer:

http://www.sercc.com/education_files/barometer.pdf

Materials: Small glass jar or can (1 per student), large balloon (1 per student), rubber band (1 per

student), scissors, tape, small stirring stick, index card (1 per student)

Suggested Activity: 5 th - 8 th grade: Briefly introduce Dalton’s Laws of Partial Pressure. See the

respiration example (In Respiration and In Therapy) for a possible connection and method of

explanation: http://www.sercc.com/education_files/barometer.pdf

3. Demonstration: Density Column

A. Mix rubbing alcohol with one drop of food coloring (ex: green) so that it can be easily

distinguished from the other layers.

B. Set up the density column in the following order from bottom to top (allows for quick

separation): honey, corn syrup, dish soap, vegetable oil, rubbing alcohol/food coloring mix,

lamp oil. Different layers will form based on the relative densities of the liquids.

C. Pre-Lab Question: Ask students to explain (based on what they have learned so far about

density) what caused the liquids to separate in layers.

D. Explain that differences in densities of the liquids caused the formation of layers.

E. Pre-Lab Question: Ask students to predict where the following objects would fall: ping

pong ball, soda cap, bead, popcorn kernel, nail

F. Drop the items in one at a time. Explain that you can determine the relative densities of

the objects based on where they fall (Objects only float on a liquid if the liquid is less dense

than the object).

Variations to Try: If the students are older, have them complete a density calculation. Prior to class,

create a table with the densities of the liquids in the density column (see page 12). Ask students to

measure out a specific volume of each liquid and weigh it. Have students calculate the densities of

the liquids based on the measurements. Compare the calculated densities to actual densities.

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4. Demonstration: Does an Orange Float or Sink?

A. Fill a clear bucket with water to about ½ inch from the top of the bucket.

B. Pre-Lab Question: Show students the orange and ask them to vote on whether they think

it will float or sink. Tally the votes on the board.

C. Result: Orange floats with the peel on

D. Remove the peel and ask students to vote on whether they think the orange will

float or sink.

E. Result: Orange sinks with the peel on

F. Pre-Lab Question: Ask students how they might explain the observed results.

G. Demonstrate density by showing two similarly sized objects with very different densities.

Pass the items around as you are explaining the demonstration.

H. How it works:

i. The orange floated initially because the pores on the peel made it less

dense than water. Objects less dense than water float (on water).

ii. The orange sunk when the peel was removed because it has a higher

density than water. Objects more dense than water sink (on water).

5. Class Activity: Dancing Lemon Seeds

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A. Pass out small clear cups and fill them with seltzer water.

B. For best results, pass out a lemon seed to each student soon after filling the cups with

seltzer water.

C. Fill one larger clear cup for the demonstration. Remind students not to touch the

materials.

D. Pre-Lab Question: Ask students if they think the lemon seeds will float or sink.

E. Ask students to place the lemon seeds in the cup and wait.

F. Result: The lemon seeds appear to “dance”, bouncing up and down in the cup.

G. Pre-Lab Question: Ask students to explain the observed results.

H. How it works: The lemon seeds sink initially because they are denser than water. The

reason for the “dancing” is that the carbon dioxide bubbles (carbonation) attach to the ridges

of the lemon seeds, carrying them up to the surface. The lemon seeds sink when the carbon

dioxide bubbles “pop” at the surface and release the lemon seeds.

Variations to Try: Pasta, raisins, or anything with a ridge may be substituted for the lemon seeds.

6. Demonstration: Card Trick

NOTE: Directions D and E assume that the demonstrator is right-handed

A. Fill an Erlenmeyer flask about ½ full with water (you can add more water once

you are more familiar with the demonstration).

B. Pre-Lab Question: Ask students how to prevent the water from spilling by just using the

playing card.

C. Cover the mouth of the Erlenmeyer flask with a playing card.

D. Hold the Erlenmeyer flask in your left hand and press against the playing card using

your right index and middle fingers.

E. Hold the Erlenmeyer flask upside down for about 10 seconds.

F. Pre-Lab Question: During the 10-second interval, ask students what they think would

happen if you removed my fingers.

G. Remove fingers. Result: The force of air pressure prevents the water from spilling out.

H. Pre-Lab Question: Ask students to explain the observed results.

I. How it works: Air pressure pushes upwards against the playing card, keeping the

water inside the Erlenmeyer flask. The water does not spill out until the force of gravity is

greater than the air resistance.

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CLEANUP: The density column contains lamp oil, a flammable waster liquid.

1. Discard hard-boiled egg and shell and matches. Reuse birthday candles. Rinse Erlenmeyer

flask.

2. Collect and recycle paper towel balls and soda bottles.

3. Do not pour liquid down the drain (flammable waste). Store liquid in another container.

Rinse and recycle objects. Rinse Erlenmeyer flask.

4. Discard orange and water (may be discarded down the drain).

5. Discard lemon seeds in the trash. Seltzer water may be discarded down the drain. Recycle

plastic cups.

6. Discard water. Allow card to dry and recycle (do not reuse for this demonstration- damaged

by water). Rinse Erlenmeyer flask.

NOTES: See page 10 for student instructions for the class activities: Dancing Lemon Seeds and Bet

You Can’t. 5th-8th grade worksheet may be found on page 11.

REFERENCES:

"Collapsing Can Experiment." Collapsing Can Experiment. N.p., n.d. Web. 12 Jan. 2014.

http://scifun.chem.wisc.edu/homeexpts/COLLAPSE.html (Can Crusher)

"Density Column." Density Tower. Steve Spangler Science, n.d. Web. 06 Jan. 2014.

http://www.stevespanglerscience.com/lab/experiments/density-tower-magic-with-science

(Density Column)

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Alex BishopDensity and Air Pressure 1/8/14"Density." - The Physics Hypertextbook. N.p., n.d. Web. 28 Jan. 2014. http://physics.info/density/

(Densities Table)

"Does an Orange Float or Sink? Density Science Experiment for Kids." Does an Orange

Float or Sink? Density Science Experiment for Kids. N.p., n.d. Web. 07 Jan. 2014.

http://www.sciencekids.co.nz/experiments/orangefloatorsink.html (Does An Orange Float

or Sink?)

"Egg in the Bottle Upside Down Twist." Steve Spangler Science. Steve Spangler Science,

n.d. Web. 07 Jan. 2014. http://www.stevespanglerscience.com/lab/experiments/egg-in-

bottle (Upside Down Egg in the Bottle)

"Floating Water." Steve Spangler Science. Steve Spangler Science, n.d. Web. 07 Jan.

2014. http://www.stevespanglerscience.com/lab/experiments/floating-water-mystery (Card

Trick)

Kline, Michael. "The Weather Map." Infotoons. N.p., n.d. Web. 13 Jan. 2014.

http://dogfoose.com/infotoons/ (Air pressure cartoon)

Lipper, Aurora. "5 Ways to Demonstrate Air Pressure to Children." ASME: Engineering Standards

News and Resources for Engineers. Mechanical Engineering Magazine, n.d. Web.

https://www.asme.org/career-education/articles/k-12-grade/5-ways-to-demonstrate-air-

pressure-to-children 10 Jan. 2014. (Bet You Can’t)

“Mass." Merriam-Webster. Merriam-Webster, n.d. Web. 09 Jan. 2014. http://www.merriam-

webster.com/dictionary/mass (Definition)

“Matter." Merriam-Webster. Merriam-Webster, n.d. Web. 09 Jan. 2014. . http://www.merriam-

webster.com/dictionary/matter (Definition)

“Volume." Merriam-Webster. Merriam-Webster, n.d. Web. 09 Jan. 2014. . http://www.merriam-

webster.com/dictionary/volume (Definition)

"ZOOM . Activities . Sci . Dancing Raisins | PBS Kids." ZOOM: PBS Kids. PBS

Television, n.d. Web. 06 Jan. 2014.

http://pbskids.org/zoom/activities/sci/dancingraisins.html (Dancing Lemon Seeds)

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http://pbskids.org/zoom/activities/sci/dancingraisins.html

https://www.asme.org/career-education/articles/k-12-grade/5-ways-to-demonstrate-air-

http://www.stevespanglerscience.com/lab/experiments/egg-in-%20%20%20%20%0D%20%20%20%20%20%20%20%20%20%20%20%20%20bottle

http://www.stevespanglerscience.com/lab/experiments/egg-in-%20%20%20%20%0D%20%20%20%20%20%20%20%20%20%20%20%20%20bottle

http://physics.info/density/


Fun Sheet (K-4th grade)

1. Why don’t we feel air pressure?

2. Why does the atmosphere split into layers? (Hint: Think of the liquid layers demonstration)

3. Does hot air float or sink? What about cold air?

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Student Instructions

Dancing Lemon Seeds

A. Place the lemon seeds in the cup.

B. Wait to see what happens.

Bet You Can’t

A. Lay the soda bottle horizontally on a table.

B. Roll a piece of paper towel into a ball about half the size of the mouth of the soda bottle.

C. Set the paper towel ball in the neck of the soda bottle on the edge (see below).

C. Take a deep breath and blow as hard as possible to try to move the paper towel ball into

the soda bottle.

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Student Worksheet (5th-8th grade)

1. What are the factors that affect atmospheric pressure?

2. Explain Dalton’s Laws of Partial Pressure and how they relate to breathing.

3. Why do we not feel air pressure?

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Table of Densities (Variation to Try)

Liquid DensityLamp Oil 760 kg/m3

Rubbing Alcohol 786 kg/m3

Vegetable Oil 918 kg/m3

Dish Soap 932 kg/m3

Corn Syrup 1380 kg/m3

Honey 1420 kg/m3

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Density and Air Pressure Teacher Kit