WaterWorks Demos-w Scripts

WaterWorks Science Demonstrations

1) Water Molecule & States of Matter Demo:

Goal:

To demonstrate and explain the states (phases) of water.

Materials:

1 ‘cup’ (7 oz) of magnetic water molecules

Magnetic white board (optional)

1 bag with 1 ml (0.034 oz) of water in it

1 bag with 1600 ml (54 oz) of air in it

Whistling kettle (optional)

Setup:

Ahead of time: o Fill 2 bags (1 ml (0.034 oz) of water in one; 1600 ml (54 oz) of air in other) o Make Ice ring crystal structure with 6 of the magnetic molecules

Just as demo begins (optional): o Fill & plug kettle in

References:

States of matter - http://www.chem4kids.com/files/matter_states.html

3 states of water Illustration (Icebergs) - http://wps.prenhall.com/wps/media/objects/165/169061/GIFS/AACQJA

L0.JPG

The water molecule - http://www.lsbu.ac.uk/water/molecule.html

Includes link to ‘Jmol’ interactive water molecules (if you have 3D red/blue glasses, try them out) - http://www.3dchem.com/molecules.asp?ID=234#

Molecular properties of water & illustrations (Lawrence Livermore

National Library, USA) - http://www-cmls.llnl.gov/?url=about_cmelsprint&content=data/pages/science_and_technology/chemistry/water_str

.xml

These activities can only be used by clients that have leased WaterWorks traveling exhibit from Science North. 1

Script:

Science demonstrator speaking = B:

Audience member(s) speaking = A:

Diagram Source: http://wps.prenhall.com/wps/media/objects/165/169061/blb9ch0102.html

B: How do we go from one phase of water to another, starting with ice?

A: Heat it?

B: That’s right! When we heat it, we add energy to the ice. This excites the molecules, or the little bits that make up water, so they spread out a little bit.

Ice melts at 0 °C (32 °F). [Ask for volunteer]

B: So these little red and white things are model water molecules. Now I’m giving them to you in a nicely organized crystal structure (rings of 6 molecules), which represents water in a solid state. Can you see the very organized rings?

This is water in its frozen state – ice. Where else have you seen frozen water today?

A:

A: in the Snowflake exhibit the Science Centre building

B: Can you show me what they would look like as liquid water? [Have volunteer complete task.]

B: Great! See how they are clumped closer together? They aren’t in a rigid structure anymore. That’s how liquid water is able to flow over things. So this is what happens when the snow melts in the spring, and turns into water.


B: Now I need someone else to help me out this time. We’re going to heat up the liquid water some more, adding more energy to the water. Thus, the water molecules are going to get more excited, jiggle around some more, and spread out even more! This will convert the liquid water-to-water vapor, which happens at 100 °C (212 ºF). Does anyone know what this process is called?

A: vaporization

B: That’s right, now [to volunteer #2] can you show me what the water molecules would look like in the vapor (gas) phase?

[Have volunteer complete task. Put away water molecules.]

B: Wow! Those molecules sure do spread out! Let’s take a look at these two bags here [pull out 2 bags] . Inside this one bag (the bag of water), there is 1 ml of liquid water. If we were to convert it all to water vapor, we have 1600 ml worth of water vapor. That is equal to the amount of air in this bag (the bag of air) over here. What a big difference! [Kettle should start to whistle around this point. Let the audience listen to the whistle sound and examine the kettle for a moment (make sure no one burns him or herself on the water vapor). Unplug kettle.]

B: Wow, did everyone hear that noise the kettle made? Can anyone tell me why it made this sound?

A: the water boiled and the steam made the whistle work

B: But how? We put liquid water into the kettle, and plugged it in. This heated the water, adding energy to the water molecules, causing them to spread out.

When the water got hot, what started happening to it?

A: it vaporized

B: That’s right! As the water molecules spread out, they took up more room, just like you saw in the 2 bags. This created a lot of pressure, forcing the vaporized water molecules out of the kettle quickly, and this produced the whistling sound! Can any of you whistle? [Encourage audience to whistle]

B: You’ve just applied the same principle that makes the teakettle whistle. You are forcing air through a small opening, your pursed lips, which produce the whistling sound.


2) Cloud in a Bottle Demo:

Goal:

To demonstrate and explain what clouds are made of.

To demonstrate the relation between pressure and temperature in gases

(i.e. the role of adiabatic heating and cooling in the formation of clouds)

Keywords: Water vapor, condensation, condensation nuclei, clouds

Duration:

4 minutes

Materials:

One 2-litre pop bottle (with a lid)

1 match

Warm water (to fill the bottle about 1/3 of the way)

Setup (about 5 minutes before demo begins):

Fill the pop bottle 1/3 of the way with warm water; put lid on

Allow bottle to sit for several minutes (to allow air in bottle to become saturated with water vapor)

References:

All about clouds: http://www.weatherwizkids.com/cloud.htm

, http://www.metoffice.gov.uk/education/secondary/students/clouds.html

What are clouds made of: http://weathersavvy.com/Q-clouds1.html

, http://www.news.wisc.edu/13675

Cloud formation (good illustration): http://www.srh.noaa.gov/jetstream/synoptic/clouds.htm

Basics & cloud formation in space settlements: http://www.nas.nasa.gov/About/Education/SpaceSettlement/teacher/les sons/tugrul/cloud/

Cloud formation and adiabatic processes: http://ocw.mit.edu/OcwWeb/Earth--Atmospheric--and-Planetary-

Sciences/12-003Fall-2007/Labs/detail/lab1-07.htm

, http://daphne.palomar.edu/jthorngren/adiabatic_processes.htm

, http://apollo.lsc.vsc.edu/classes/met130/notes/chapter6/adiab_warm.ht

ml

Cloud formation in depth: http://www.weatherexplained.com/Vol-

1/Weather-Fundamentals.html

(scroll about ½ way down), http://members.aol.com/pakulda/atpptnts.htm

How to (various methods): http://www.exploratorium.edu/snacks/fog_chamber.html

(in a jar), http://www.ecologycenter.org/tfs/lesson.php?id=13464 (focuses on fog), http://www.stevespanglerscience.com/content/experiment/00000030

(using a bicycle pump), http://bizarrelabs.com/cloudb.htm

(in a jar)


Relationship between pressure, temp. & volume of gases - http://www.chemistry.ohio-state.edu/betha/nealGasLaw/fr1.3.html

(animation), http://en.wikipedia.org/wiki/Gas_laws

Script:


Audience member(s) speaking/answer = A:

B: Does anyone know what the 3 states of water are? Can you give me examples?

A: Solid (ice), liquid (water) and gas (vapor).

B: The cool thing about water is that it’s pretty much the only chemical that we naturally encounter in these 3 states. During the winter, you can walk out and see snow and ice on the ground, maybe a puddle or a dripping icicle, and there is always invisible water vapor (gas) in the air around us.

B: Has anyone ever looked up and wondered what clouds were made of? What do you think they’re made of? A: Liquid and solid water.

B: Since water vapor (gas) is invisible, the clouds we see are made of liquid and solid water. So, what you’re seeing when you look up is innumerable number of water droplets, water crystals, or a mixture of the two.

B: What I have here is a bottle with warm water at the bottom [Pull out prepared water bottle] . What do you think is in the air in the bottle? A: Water vapor.

B: So, we have liquid, solid and gaseous water around us down near the ground; how do you think water crystals and droplets get all the way up to where you see clouds?

A: Water evaporates into the atmosphere.

A: Water vapor cools and condenses and/or freezes as it rises in the air.

B: Like we said earlier, water vapor is all around us. This is because water near the ground is constantly evaporating. The cycles of day and night allow water vapor to rise as the air heats up during the day. As the warm air rises in the atmosphere it cools, and the water vapor condenses onto particles (e.g. dust) in the atmosphere. Many of these together form a cloud.

B: I’m going to light a match, and drop it into the bottle [do it – let the match burn a bit, blow it out, drop it in & close the lid] . So, what do I have in the air in the bottle now?

A: Smoke…a cloud of smoke.

B: I’ve added smoke particles to the air in the bottle.


B: Now, I’m going to squeeze the bottle and apply pressure to the contents [do it – the air should go clear] . Notice that the air goes clear? When I release the pressure, watch what happens [do it – the cloud will get more apparent after you do it a few times] .

B: What did you see when I released the pressure on the bottle? A: A cloud.

B: Right, it was a cloud of condensation – liquid water droplets condensed on the smoke particles.

B: This condensation is the same thing that happens on the outside of a cold glass

- the water vapor in the air condenses to liquid water on the outside of the glass.

If the contents of the glass are really cold, the condensation freezes, and you get frost on the outside of the glass.

B: So, to make the cloud appear and disappear, I apply and release pressure in the bottle. [Keep performing the demo] What do you think is happening?

B: The cool thing about air is that when it is compressed it warms, and when it expands it cools. This is called ‘adiabatic’ heating and cooling. [Keep performing the demo] As air rises it expands, and as it expands it cools. As the air cools, the invisible water vapor condenses into liquid water that we can see as clouds.

If the air rises high enough, it becomes cold enough and it freezes into ice crystals.

B: So, as I compress the bottle [repeat demo] , I am warming the moist air. As I release the pressure, the air cools (cool air can't hold as much water vapor as warm air) and some of the vapor condenses onto the smoke particles (i.e. condensation nuclei) and form tiny droplets around each dust particle. When billions of these droplets come together they become a visible cloud.

B: FYI: The relationship between pressure and volume is expressed in the formula:

Where:

P is the pressure (SI unit: pascal)

V is the volume (SI unit: cubic meter)

T is the temperature (SI unit: kelvin)

NOTES: We have tried variations using external pumps, but we find that it makes the experiment more elegant and simplified to use only the capped pop bottle

(i.e. a closed system, with limited variables).


3) Hydraulic Syringes Demo:

Goal:

To demonstrate and explain the compressibility of air and the incompressibility of water.

Duration:

4 minutes

Materials:

6 - large clear plastic syringes

2 - lengths of clear plastic tubing (fit snugly over the syringe nozzles), each about 40-50cm (16-20 in) long

Photographs of a hydraulic machines (e.g. car jack, backhoe, lowrider)

Towel (for possible leaks)

Food coloring (optional)

Water

Setup:

Pull back the plunger of one syringe to half-fill it with air.

Attach this syringe to another syringe that has the plunger pushed all the way in using one length of surgical tubing (refer to the diagram below).

Connect two more syringes together in the same way, but filling both the tubing and the open syringe with colored water (using the food coloring), so that there is little to no air in the system once it is connected.

Fill a fifth syringe with air to 30mL (1.014 oz), and leave it separate.

Fill the sixth syringe with 30mL (1.014 oz) of colored water, and also leave it separate.

References:

For an explanation of hydraulic principles, check out: http://www.grc.nasa.gov/WWW/K-

12/WindTunnel/Activities/Pascals_principle.html

Script:



B: Has anyone here ever shot water out of a Supersoaker? [Count hands] Okay, how many of you have ever gone swimming and put your head underwater?


Oh, lots of you! So you guys already have some experience with water pressure then!

B: Okay, I need two volunteers. [ if possible, choose a small child and a stronglooking adult ]. I have two syringes here, one filled with 30ml of air, and one filled with 30ml (1.014 oz) of water. I’m going to give each of you a syringe, and I’d like you to cover the nozzle with your finger, and see how much you can squish the contents by pushing on the plunger. [ Give air-filled syringe to child, and water-filled syringe to adult ]. Okay, and go! [ The volume of air inside the syringe will decrease, but the volume of water in the other syringe will not, regardless of how much pressure is applied ]

B: [ To child ]: Wow, you’re really strong! (volunteer’s name) squished, or compressed, the air inside this syringe down to (x) ml (oz).

B: [ To adult ]: What about your syringe – were you able to compress the water?

A: No.

B: Would anybody else like to try compressing water? [ let another volunteer try

– no one will be able to ]. Why do you think we can compress air, but not water? [ help audience to provide the answer if they can ] Well, air molecules are quite far apart, and so by applying pressure, (first volunteer’s name) were able to push the air molecules closer together so that they took up less space.

There was still the same amount of air, but it was pushed into a smaller volume. So we say that air is compressible. Water molecules are already really close together, so even with a lot of pressure, we can only move them slightly closer together. So we call water an incompressible fluid.

B: Let’s see now how these differences in compressibility affect simple machines. I need two more volunteers. [ Hand one audience member the attached air-filled syringes, and a second audience member the attached water-filled syringes. Have your volunteers hold one syringe in each hand, and place their thumbs on the ends. Then instruct them to push down on the full syringe, causing the empty syringe to fill. They can continue pushing the contents (air or water) back and forth between their two attached syringes.

]

B: Do either of you feel a delay when you push down one syringe? [ Air syringes will be delayed.

]

B: (Volunteer’s name) can feel a delay between the syringes with air because that air is compressible, and its volume can be reduced before it is pushed along the tubing into the other syringe.


B: [ To volunteer with water-filled syringes.] Do you feel a delay?

A: No.

B: Why do you think (volunteer’s name) doesn’t feel a delay between her syringes?

A: Because water isn’t compressible.

B: Very good! Because water is incompressible, pushing in one syringe will instantly cause the attached syringe to rise.

B: You will notice that the water has to travel through a narrow tube to do this.

When the water is pushed through a narrow tube, its pressure increases, and we can use this pressure to help us move heavy objects. Does anyone know what we call machines that use incompressible fluids to do work for us?

A: Hydraulics.

B: Absolutely! And we use hydraulics a lot in our society, like in car jacks [ show picture ], backhoes [ show picture ], and even to make cars dance [ show lowrider car picture ]. If you haven’t had a chance yet, you can use a hydraulic lift to raise yourself up on a chair using water pressure in the exhibit hall.

[ Chair works by pumping water into narrow pipes to create high pressure, which pushes the chair up because it cannot push the water down since water is incompressible.

]


4) Eardrum Demo:

Goal:

To show why we feel pressure in our ears when we dive under water.

Duration:

4 minutes

Materials:

1 - tall, clear plastic cylinder (about 20cm (8 in) diameter & 2m (6.5 ft) tall) in stand. Filled with water.

1- wooden doweling rod, approximately 1m (3 ft) in length

1 - glass baby food jar, attached on its side to the doweling rod using silicone or crazy glue

1 - pink balloon

1 - permanent black marker

2 - elastics

Photograph of a human ear (showing where the eardrum is located), a swimmer and a diver

Towel (for possible leaks)

Extra balloons

Water

Setup:

Fill the large cylinder with water up to approximately 30cm (12 in) from the top.

Position this cylinder so that audience members will be able to see the bottom.

Cut a flat piece of latex from the balloon, and stretch this over the mouth of the baby food jar.

Secure the latex around the jar’s mouth using the elastics.

Draw an X across the mouth using permanent black marker.

Periodically check that the balloon latex is still stretched tightly over the mouth of the baby jar, and that it has no rips in it, and no water inside it.

If you notice any rips, replace the balloon, making sure you draw another X across the mouth, and that the inside of the jar is dry.

Safety Precautions:

Audience members can practice equalizing their ears, but it is important to stress that they should only blow very lightly, and should feel their ears pop easily. You should never force it, or attempt this when you have a cold.

References:

For an explanation of why water pressure changes with depth, and also how this affects divers, check out: http://van.physics.uiuc.edu/qa/listing.php?id=2232

These activities can only be used by clients that have leased WaterWorks traveling exhibit from Science North.

10

For an explanation of how compressibility and water pressure would affect a theoretical object lowered very deep into the ocean, check out: http://van.physics.uiuc.edu/qa/listing.php?id=2251

Script:



B: Has anyone here ever swum underwater? [ Hold up pictures of swimmer and diver ] A: Yes!

B: Really? And when you were underwater, did you ever feel pressure on your ears? A: Yes!

B: Let’s see if we can figure out why that happened. So just like in the syringes, we have air inside our bodies. And if we apply pressure to that air, what do you think will happen to it?

A: It will be compressed/squished.

B: That’s right! And can water be compressed? A: No!

B: Right! Water can’t be compressed, but it can create pressure. And the more water above you, the more pressure it creates, because the water pushes downwards. So if we have a column of water [ point to water cylinder ], where would there be the most pressure? A: At the bottom.

B: Good! And where would there be the least pressure? A: Near the top.

B: Awesome! So because there is more pressure deeper in a water column, when you dive down into the water, the air in your body becomes more compressed the deeper you go. But I mentioned your ears. [ Show picture of ear ] Does anyone know why we feel these pressure changes in our ears? A: Because of our eardrums?

B: Yes! If we look at our ear [ refer to picture ], we can see that the inside, where the air is, is separated from the outside, where the water would be, by a flexible membrane called the eardrum. Now I have a model ear on a stick right here [ show model ear, pointing out air-filled inside and ear drum ]. Who would like to see what happens to this eardrum when we put it underwater?

B: All of you? Okay, now keep your eyes on the eardrum as I lower our ear into the water. [ Slowly lower model ear down cylinder, with X surface of the


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balloon facing the audience .] What happened to the eardrum? A: It got pushed in.

B: That’s right! And what pushed the eardrum in? A: The water.

B: Right! The water created pressure on the ear, which compressed or squished the air inside it and pushed in the eardrum. And was the ear compressed more at the top or the bottom of the water column? A: At the bottom.

B: Yes! And why was it compressed more at the bottom?

A: Because there is more pressure in deeper water.

B: Man, you guys are smart! But I know it’s pretty uncomfortable to have so much pressure on your ears when you dive. One way to avoid this is to equalize the pressure inside your ears as you dive with the water pressure outside. You can do this by lightly blowing out your nose while holding it plugged. [ Note safety precaution here .] This pushes more air (from your lungs) into your (inner) ear, which equalizes the pressure from the water outside that’s pushing inwards on your eardrum.

B: So now you know how water pressure works, and how it affects our bodies when we dive underwater. And if any of you played the water pinball game in the exhibit hall, you probably saw some of these differences in water pressure being used. [ if anyone wants an explanation: water at the bottom of the column shoots farther horizontally than the water at the top of the column, because the water at the bottom is under more pressure.

]


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5) Pressure Diver (Cartesian Diver) Demo:

Goal:

To demonstrate buoyancy, and to a lesser degree density and the incompressibility of liquids (versus gasses).

Duration:

4 minutes

Materials:

3 - large clear pop bottles

4 - small glass test tubes

2 - test tube corks

1 - packet of ketchup (or mustard, relish, vinegar, etc)

1 - large glass container partially filled with water

3 - pieces of wire (see diagrams in Setup section)

2 - chunks of Plasticine

Food coloring (optional)

Water

Setup:

Part 1:

Start with two corked test tubes, one empty and one almost full of water

(food coloring is optional). Make sure the empty one floats and the full one sinks.

Have the large glass container with some water in it handy to show the tubes floating and sinking.

Part 2:

Using a test tube, piece of wire and chunk of plasticine, create the apparatus shown at right:

Fill a large clear pop bottle with water and carefully place the test tube apparatus open-end-down in the water so that the air in the test tube does not escape. The test tube should float vertically in the water.

Top-up the pop bottle so that it is completely full of water and screw on the cap tightly.

Ensure that the test tube sinks when the bottle is squeezed. If it does not, add more plasticine to increase the weight until it does.

Part 3:

Put a packet of ketchup in a large pop bottle.

Fill the bottle to the brim with water so that no air remains and screw on the cap tightly.

Ensure that the packet sinks when the bottle is being squeezed and floats when it is not. You might have to try several packets to find one that has


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enough air in it to sink when the bottle is squeezed. We had success with a relish packet from the Science North cafeteria.

Part 4:

Using a test tube, two pieces of wire and a chunk of plasticine, create the apparatuses shown at right:

Fill a large clear pop bottle with water and place the plasticine and wire loop apparatus into the bottle so that it sinks to the bottom.

Place the test tube apparatus open-end-down in the water so that the air in the test tube does not escape. The test tube should float vertically in the water.

Ensure that the test tube sinks when the bottle is squeezed, and that the plasticine ball is light enough that the test tube can lift it to the surface when the squeezing stops. If the ball is too heavy, remove some of the plasticine and try again.

References:

For an interesting discussion about the different theories that kids come up with for why pressure divers work, and the murky history behind the name “Cartesian Divers”, check out: http://www.ed.uiuc.edu/courses/CI241-science-

Sp95/resources/philoToy/philoToy.html

How to (pen cap & eyedropper) & animation - http://www.seed.slb.com/en/scictr/lab/diver/index.htm

How to (pen cap & balloon) - http://www.hinduonnet.com/thehindu/yw/2003/06/07/stories/200306

0700110200.htm

How to (clear piece of straw) - http://www.abc.net.au/science/experimentals/experiments/episode7_1.h

tm

How to (test tube – squid obstructs view of bubble) - http://www.phys.utk.edu/demoroom/FLUIDS/CARTDIVER.htm

Large Diver (scroll to bottom) - http://physics.ucsc.edu/lecturedemonstrations/fl_pr_ht/pressure.html

Animation - http://hyperphysics.phyastr.gsu.edu/hbase/pbuoy3m.html#c1

Solar diver - http://www.genuineideas.com/HallofInventions/SolarDiver/diverdescriptio n.htm


14

How to (ketchup packet) - http://www.wikihow.com/Make-a-Cartesian-

Diver-with-a-Ketchup-Packet , http://www.stevespanglerscience.com/content/experiment/00000090

Script:



Part 1:

B: Okay, so we know that water is incompressible and air is compressible, and we’ve seen what happens to our eardrums when we dive under the water.

Now let’s take a look at something else we can do with water pressure and compressed air!

B: So first of all, what do you think a glass test tube full of air will do if I drop it in then water? [hold the empty, corked test tube up for the audience to see]

A: Float!

B: That’s right! It’ll float! [Drop the test tube into the glass container of water to show that it floats] But what if we put some water into the test tube and make it heavier? [Hold up the test tube full of water.] Then what will happen?

A: It will sink!

B: That’s right! [Drop the test tube into the container to show that it sinks.] So, we know that a test tube full of air will float and a test tube with too much water in it will sink.

Part 2:

B: What I have here is a bottle full of water. [Hold up the apparatus] Can you see what else is in there? [Show the apparatus out to an audience member to see up close.]

A: A test tube!

B: And is it sinking or floating?

A: It’s floating.

B: Right! It’s floating because it’s full of air. Do you remember what happened to the syringe full of air when we pushed on it?

A: It compressed!


15

B: Right! So what do you think will happen to the air inside the test tube if I push on the sides of this pop bottle?

A: It will compress!

B: That’s right! It will compress and get smaller. And water will push into the test tube and make it heavier. And if the test tube gets heavier, what will happen?

A: It will sink!

B: Hmm…it sounds like you guys really know what you’re talking about. Okay, so you’re saying that if I squeeze on the bottle, the air in the test tube will be compressed, it will push water up into the test tube and the test tube will sink.

Let’s see if you’re right. Who’s good at squeezing? [Choose a volunteer to come up.]

Okay, when I say ‘go’, give the bottle a squeeze and let’s see what happens!

[Hand the bottle to the volunteer.] Drum roll please! [Drum fingers on the table.] Aaaaaaaaand….GO!

[Volunteer squeezes, test tube sinks.]

Yeah! You guys were right! [Take back the bottle, let the volunteer sit down.]

Part 3:

B: Now, if you want to try this at home. You don’t even need any test tubes or wire. You can make a pressure diver with just a pop bottle and a packet of ketchup, or in this case relish. [Squeeze the bottle to sink the packet.] You might have to do some testing to find one that has enough air in it to work properly.

If you want to get a little fancier, you can even try making a game like this one. [Show the bottle with the hook and ring apparatus.] The goal is to hook the diver onto the sunken

treasure and bring it back up to the surface. [Squeeze the bottle to sink the diver.]

Conclusion:

B: So that’s it for now. Feel free to come up and ask us any questions you might have about water pressure or compressibility, or to try out one of the divers.

And enjoy the rest of your visit!


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6) Water Density and Temperature Demo:

Goal:

To discover how temperature affects the density of water.

Keywords: thermocline, density, lake turnover

Materials:

2 plexiglass divided containers

( http://boreal.com/product.asp_Q_pn_E_IG0029656

)

Red and blue food coloring

Water

Ice bath – shallow tray with ice (for cold water)

Small hot plate or kettle (for hot water)

Four 500 ml (17 oz) beakers

Bucket for wastewater after demonstrations

References:

Animations of lake turnover experiments with a divided tank - http://www.bellmuseum.org/distancelearning/greatlakes/seiche.html

Heidorn, K.C. 2005. Weather Phenomenon and Elements: Fall/Spring Lake

Turnover. www.islandnet.com/~see/weather/elements/turnlakes.htm

Article & Animations - http://faculty.gvsu.edu/videticp/stratification.htm

Short description & good illustration - http://www.britannica.com/eb/art-36/Annual-circulation-patterns-in-adimictic-lake

Article & Illustration (in Fahrenheit) - http://www.dnr.state.wi.us/org/water/fhp/lakes/under/mixing.htm

Scroll down for illustration (probably other good information for

WaterWorks resources) - http://www.epa.gov/glnpo/atlas/glat-ch2.html

Article & series of illustrations - http://www.rmbel.info/Reports/Static/Stratification.aspx

Favorite illustration - http://kentsimmons.uwinnipeg.ca/16cm05/1116/50-15-

LakeStratification-L4.gif

Water density calculator - http://www.csgnetwork.com/h2odenscalc.html

Setup (5 minutes prior to demo):

1. Fill a 500mL (17 oz) beaker to the 250mL (8.5 oz) line with water and add a few drops of red food coloring. Stir to mix and place on hot plate.

2. Fill another 500mL (17 oz) beaker to the 250mL (8.5 oz) line with water and add a few drops of blue food coloring. Stir to mix and place in ice bath.

3. Fill two remaining beakers to the 250mL (8.5 oz) line with room temperature water. Add a few drops of red food coloring to one and a few drops of blue food coloring to the other. Stir to mix.


17

Script:


B: Can anyone tell me what density is? Density is a measure of a substance’s mass relative to how much space it takes up (density = mass/volume)

B: We are going to start with a demonstration about the density of water.

B: I have two beakers full of room temperature water and I added a few drops of food coloring to each – one is red and one is blue. I’m going to pour the red water on one side of this divided container and the blue water on the other side of the container. Pour into one divided container.

B: What do you think will happen when the divider is removed? Why?

B: Could one of you remove the divider (quickly is best)?

B: What happens? (The red and blue colors should mix to create a purple solution throughout the container) Why? (Red and blue make purple, the water on each side had the same density so they mixed)

B: Now we’re going to do the same thing, but the red water has been heating on this hotplate and the blue water has been cooling in this ice bath. Pour the red water on one side and the blue water on the other side of the second divided container. Be careful not to burn anyone with the hot water.

B: What do you think will happen now when the divider is removed? Why?

B: Could I have another volunteer? Could you remove the divider?

B: What happens? (The red and blue colors should form layers with red on top and blue on the bottom and a little bit of a purple ‘thermocline’ in-between)

Why didn’t the colors mix ? (Cold water is denser than hot water, so it sinks to the bottom. Over time a purple layer will form in-between as the cool water warms and the hot water cools where they are in contact with each other.

The purple layer is the thermocline.)

B: Where does this happen in nature?

B: It happens in lakes. In the summer, the water in a lake is in three layers. The top layer is warm (epilimnion) and the bottom layer is cold (hypolimnion), with a moderate layer in the middle (thermocline). Show the diagram. So, what would happen in the fall as the surface layer of water cools? The cold surface water would become denser and sink into the lower layers of water. Wind action helps to circulate the water, so that the bottom water comes to the surface and the surface water goes to the bottom. This is called lake turnover.

It is an important feature of lakes to move nutrients around. It occurs in the spring and fall.


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B: Now I have an important question for you: If cold water is denser and sinks to the bottom of lakes, why don’t lakes freeze from the bottom up?

B: Water has a unique property because it reaches its maximum density at 4°C.

Ice is less dense than liquid water and therefore floats. So, in the winter, the lake stratifies again, this time with the densest water on the bottom at 4°C, with cooler water on top and ice at the surface. Then it turns over again in the spring as the surface water warms. Show diagram.

B: Extra Information (if questioned): Ice is less dense because of the way water molecules arrange themselves when they form ice crystals. The crystalline structure of ice holds molecules at greater distances from one another than when they are in a liquid form.

7) Density of Objects and Buoyancy Demo:

Goal:

To discover how the density of objects affects their buoyancy in water.

Keywords: density, buoyancy

Materials:

3 wood blocks of equal size (Balsa, Pine, Oak)

Small aquarium

Ball (or 2) of Plasticine

Water

Some coins (not necessary)

Additional materials: o Overflow container, balance/scale

References:

Buoyancy basics, Pascal’s principle & fluid pressure – http://hyperphysics.phy-astr.gsu.edu/hbase/pbuoy.html

, try the site about buoyancy-related concepts too http://hyperphysics.phyastr.gsu.edu/hbase/buocon.html

PBS NOVA On-Line. 2000. Buoyancy Basics (try the quiz to make sure you understand the principles!). http://www.pbs.org/wgbh/nova/lasalle/buoybasics.html

Archimedes’ Principle, how submarines work, buoyancy & density (with animations) - http://www.onr.navy.mil/focus/blowballast/sub/work2.htm

Archimedes’ Principle and an overflow cup to look at volumes of displaced water - http://physicslearning.colorado.edu/website_new/Common/ViewDemonst ration.asp?DemoCode=2B40.23

Buoyancy. Wikipedia. http://en.wikipedia.org/wiki/buoyancy


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Krystek, L. 1999. Plasticine Experiment with Buoyancy. http://unmuseum.mus.pa.us/exboyant.htm

How to & photos - http://www.earlytechnicaleducation.org/project_mechanic2.htm

Boat shapes - http://www.kangflatsc.vic.edu.au/home/solar/Boat_Shapes.htm



1. Fill the two 500 mL (17 oz) beakers to the 250 ml (8.5 oz) line with room temperature water. Add a few drops of red food coloring to one and a few drops of yellow food coloring to the other.

2. Fill two 1L beakers to the 750 ml (25 oz) line with room temperature water.

Script:


B: Can anyone tell me what buoyancy is? Answer: Buoyancy is the upward force on an object produced by the surrounding water.

B: Naming each type of wood, have a volunteer come up and describe which one is heaviest.

B: Have the volunteer place the wood block in one at a time, asking the audience what they think will happen in each case.

B: Discuss wood density.

B: Don’t need to talk about the raft: Ask the audience which material they would prefer to make a raft out of. If they pick the balsa, explain that the larger intercellular spaces mean that the wood becomes waterlogged faster, and that pine would be a better idea, because of its intermediate density and the waterproof resin in the wood.

B: Remove the wood blocks for the next demonstration.

B: Take out the plasticine ball.

B: Ask the audience what will happen when you drop the ball in the water. Drop the ball in when they answer, and it will sink.

B: Take the ball out and ask the audience if there is a way to make it float.

Follow a few suggestions by them, and if none work, then flatten it out and shape it into a cup.

B: Explain that rafts float because the materials used to make them are less dense than the water. But boats are often made of metal, which is denser than water. Explain that boats float because their shape encloses an airspace,


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which means that the boat is less dense than water, even if the material that it is made out of is denser (if you’re having trouble with the explanation, go back to

B: Additional – drop pennies (or something) into your boat until it sinks.

B: Ask what happened. The weight of the boat increased until the weight of the water it was displacing became less than the weight of the boat…it sunk.

B: Additional – Try using an overflow container (see ‘references’ above for setup ideas) to show the volume of water displaced by various objects. You can also use a balance to weigh the object that is displacing the water, and the amount of water that is displaced (to show that the weights are the same).


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8) Water Density and Salinity Demo:

Goal:

To discover how salinity affects water density and the buoyancy of objects.

Keywords: halocline, density

Materials:

1 plexiglass divided container

( http://boreal.com/product.asp_Q_pn_E_IG0029656

)

Two 1L beakers

Two 500 ml (17 oz) beakers

Water

Salt

Spoon (to mix salt)

Red and yellow food coloring

Block of oak

Straw, Plastine & Sharpie marker to make a hydrometer (optional)

References:

Buoyancy - http://en.wikipedia.org/wiki/buoyancy

Plasticine Buoyancy Experiment - http://unmuseum.mus.pa.us/exboyant.htm

PBS NOVA Buoyancy Basics (try the quiz to make sure you understand the principles!) - http://www.pbs.org/wgbh/nova/lasalle/buoybasics.html

How to (make a hydrometer out of a straw) - http://www.teachers.ash.org.au/jfuller/liquids/hydrometers.htm

, http://www.grandpapencil.net/science/hydrom.htm

, http://wow.osu.edu/experiments/statesofmatter/psm2/hydrometers.htm

l

The Arctic Halocline - http://www.whoi.edu/oceanus/viewImage.do?id=38468&aid=19787 , http://www.divediscover.whoi.edu/arctic/circulation.html# (#2 on the map)



1. Fill the two 500 ml (17 oz) beakers to the 250 ml (8.5 oz) line with room temperature water. Add a few drops of red food coloring to one and a few drops of yellow food coloring to the other.

2. Fill two 1L beakers to the 750 ml (25 oz) line with room temperature water.

Script:



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B: Can anyone tell me what density is? Density is a measure of a substance’s mass relative to how much space it takes up (density = mass/volume)

B: Does anyone know of another way to alter the density of water? Answer: salinity. Now we’re going to try this again, but we’re going to use room temperature water for both sides again, but we’re going to add a little salt to the yellow water. Ask a volunteer to add 1 teaspoon of salt to the yellow container and stir it until dissolved. Pour the red water on one side and the yellow water on the other side of the divided container.

B: What do you think will happen now when the divider is removed? Why?

B: Could I have another volunteer? Could you remove the divider?

B: What happens? (The red and yellow colors should form layers with red on top and yellow on the bottom and a little bit of orange in between. The orange part is the ‘halocline’.) Why didn’t the colors mix ? (Salt water is denser than freshwater, so it sinks to the bottom)

B: Now we’re going to look at a combination of buoyancy of objects and density of water.

B: I have 2 beakers of room temperature water, filled to exactly the same level.

Ask a volunteer to add 3 teaspoons of salt to one of the beakers and mix until dissolved.

B: I’m going to drop the block of oak into this beaker. Ask a volunteer to read the water level on the beaker.

B: Now, if I put the same block into the beaker of salt water, what do you think will happen? I’ll give you a hint: has anyone ever swum in the ocean? What did you notice? (Answers will probably indicate they floated better – more buoyant)

B: Ask a volunteer to read the water level on the beaker (it should be less because the block displaced less water).

Which block is more buoyant? Why?

(The block in salt water should be more buoyant because the salt water is more dense and therefore exerts a greater force upward on the object; in other words, the difference in density between salt water and the block is greater than the difference in density between freshwater and the block)

B: Additional Experiment: Make a hydrometer out of a piece of straw and some Plasticine (see references above), and try it out in the fresh and salty water samples.


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9) Groundwater Model Demo:

Goal:

To demonstrate and explain how groundwater flows, and groundwater contamination.

Keywords: Groundwater, aquifer, well, contamination

Duration:

Depends how long people want to interact

Materials:

Groundwater model

Pump and container assembly

Wrench

Water

Food-coloring (= contamination/pollution)

Setup:

Fill the model with water (all the way to the surface of the ‘ground’)

Resources:

About groundwater models: http://www.co.portage.wi.us/Groundwater/teach/gwmodel.htm

; http://groundwater.unl.edu/standard.html

; Groundwater Model Project http://www.uwsp.edu/stuorg/awra/h2omodel.html

Groundwater model activities for students: http://www.wvca.us/education/groundwater_model/ (very good site!); http://www.waterresearch.net/Waterlibrary/groundwater/groundwatermodel.pdf

About the model:

This is an average-looking cross-section of ground

There is no bedrock

This ground is typical of glacial deposits (sand and gravel)

An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using water well. The study of water flow in aquifers and the characterization of aquifers are called hydrogeology. Related terms include: an aquitard, which is an impermeable layer along an aquifer, and an aquiclude (or aquifuge), which is a solid, impermeable area beneath an aquifer. The surface of saturated material in an aquifer is known as the water table. (source = Wikipedia)

There is a deep clay layer that separates, or ‘confines’, an aquifer. The clay layer is called a ‘confining layer’ and it creates a ‘confined aquifer’ below it. o Confined aquifers are often under pressure because of thousands of years of water seeping in and being confined.


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o Artesian wells come from confined aquifers. If these are tapped, they may not replenish quickly. Since Walkerton, these have begun being mapped more.

There are 2 types of wells : o Shallow wells are less than about 25 feet, because pumps placed on the surface can only pump water from about 27 feet down.

These wells may be rather large in diameter, because a person may have to go down into them to clean them, etc. o Deep wells are narrower in diameter, and they contain a submerged pump. They go as deep as is necessary (150 – 200 feet) to reach water. Very expensive to drill.

Groundwater generally flows. This is the principle being displayed by this model. The underground water table

Since groundwater is not static, if the ground becomes polluted or contaminated with something like pesticides, these can sink into

(permeate) the ground, and contaminate the groundwater. Since the water is all connected underground (the water table), contaminants can travel from one area to another, and be drawn up in a distant well.

Around the place where water is drawn into a well, a ‘cone of influence’ is created as water is drawn from all directions towards the well.

Groundwater clean up is expensive (sometimes millions of dollars). It can also take many, many years. What we must do is to prevent contamination from occurring (source: http://www.gem.msu.edu/gw/lessons/gwmodel2.html

): o Conserve water. o Properly use, store and dispose of fertilizers and pesticides. o Clean and maintain septic systems. o Check underground storage tanks for leaks, o Properly dispose of used car oil and other household hazardous products. o Reduce, reuse and recycle. (The making, transporting, and disposing of products cause many water pollution problems as well as other environmental problems.)


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