Stem Seminar

Discrepant Events

Peter Shaughnessy

March 2007

petersh@k12s.phast.umass.edu

E-mail contact (if you have a question please ask it)

Note: click the bird to get back here.

Mt Holyoke College

• ChemKit Program– Contact Information– To borrow one of these kits please contact

Edward Fitzgerald at 413-538-2398.– Requirements for Borrowing Kits– Kit Descriptions

Discrepant Events

These are interest-arousing and often

surprising phenomena that cause one to wonder about the

science concepts being presented

Activities Discrepant Events

Discrepant Events Main MenuDemonstrations ListPatterns and Learni

ngPlastic Bottles

Flashy Solid

Methane Can

Jarring Surface Tension

Penny Eats Metal

Drinking BirdSupercool Liquid Releases Heat

Activities List

Activities1 Vanilla Balloon2 Alcohol and Water3 Hot and Cold Water4 Rates of Evaporation5 Feeling Your Alcohol6 Water Mosh Pit

7 Taping the Charge8 Polar Water

9 Non Polar - Polar10 Probing Water

11 Heavy Metal Tension 12 Reaction Rates

Discrepant Events

Adding Vanilla to Balloon

Vanilla liquid begins to evaporate and form a gas.

Vanilla molecules are sensed outside the balloon. What does it all mean?

1 Vanilla in Balloon

Talking Points - • Liquids change to gases• Gases move from place to place• Latex Balloons have unseen holes • Molecules of vanilla are small• Molecules have different sizes• To smell something your nose has to be

struck by a molecule.

Activity Menu

2 Mixing Alcohol and Water

Observations

• Mixing equal volumes of water and ethanol and you get a total volume that is less than the sum of the two equal volumes.

• Heat is released.

• A gas bubble appears.

Talking Points of Alcohol and Water Mixture

Water is more dense than alcohol

Molecules are different sizes

When water and alcohol mix heat is released

The heat generated vaporizes some of the liquid mixture called a solution.

Activity Menu

3 Temperature and Molecular Motion

Translational Movement

Rotational Movement

Vibrational Movement

Gases

Gases, Liquids

Gases, Liquids, Solids

5 sec

25 sec 35 sec

15 sec

Activity Menu

4.Evaporation Rates

• Observations– Alcohol evaporates faster in warmer rather

than colder environments

• Talking Points– Molecular attractions– Average kinetic energy– Comparative rates of evaporation (water)

4 + 5 Evaporation Rates

Intermolecular Attractions

Kinetic Energy

Relative Humidity

Dynamic Equilibrium

Activity Menu

6 Water Thermometer: The Mosh Pit

Alcohol filled bulb

Temperature Scales

oC = Celsius

oF = Fahrenheit

In a warmer environment the liquid alcohol expands due increased kinetic energy of the alcohol molecules taking up more space. The molecules do not get bigger

Space inside thermometer above the alcohol is a vacuum meaning there is nothing there!

For a thermometer to work it must be struck by particles which either impart more energy or take energy from the thermometer.

If the thermometer loses energy the liquid contracts and takes up less space and conversely if it gains energy the liquid inside takes up more space.

Water Thermometer

• Observations– Colored water rose in tube with warmer temperatures

and went down with colder temperatures.

• Discussion Points– Molecular motion at higher and lower temperatures.– Molecules created a larger space around themselves

be careening into others at higher temperatures.– Did the molecules get bigger? Or just create more

space.

Activity Menu

7 Taping the ChargeAtoms

Protons Electrons

Positive charge +

Negative charge -

Found in the nucleus

Found outside the nucleus

Summary of Taping the Charge

A Thing Called Charge Exists

There Are Two Kinds of Charge

Summary of taping the Charge

Electrons can be removed from atoms by rubbing or touching.

Like Charges Repel

Negative repels Negative

Positive repels Positive

Opposite Charges Attract

Positive attracts Negative

Negative attracts PositiveActivity Menu

8 Visual of Demonstration of the Dipole Properties of Water

Bending Water Movie Site

Activity Menu

9 Polar and Non-polar Liquids

• Demonstrates– Density differences- oil, water, – Likes dissolving in likes, miscible properties– Polar not dissolving in Non-Polar, immiscible

1.Oil

2.Oil, water

3.Oil, water, food color

3.Oil, water, food color

Activity Menu

10,11, Heavy Metal Causes Tension

What Shape Does a Water Molecule Have?

H H

O

HH

O

++

=

Between Molecules Only

Briefly Hydrogen Bonds in Water are Responsible for:

High Boiling Point of water

High Freezing Point of Water

High Surface Tension of water

High Cohesive forces of water

Ability to expand on freezing

Surface Tension

The forces of attraction between water molecules on the surface of the liquid are greater than those below the surface.

Water Strider

Photo by:George I. Bernard/Animals Animals

Water Strider, common name applied to slender water bug (see Bug) that is a predator on other insects. It lives on the surface of quiet waters-some species are adapted for life on faster-moving streams-and darts about with great rapidity, using the middle pair of legs as paddles and the hind pair for steering. The front pair of legs is adapted for grasping prey. Fine, dense hairs on the feet keep the insect from breaking the surface tension of the water

Scientific classification: Water striders belong to the family

Gerridae, of the order Hemiptera.

But most importantly it lets this animal do its thing!!

Jesus Lizard Runs on Water

Thanks to surface tension due to Hydrogen Bonds

Activity Menu

Alka-Seltzer Reaction Rates

• Observations– Heat accelerates rate of chemical reaction– Increasing surface area increases rate of

reaction.

• Talking Points– Increased kinetic energy increases frequency

of particles hits.– Increased number potential reactants

increases frequency of reactionAspirin, Sodium Bicarbonate, and Citric Acid

Activity Menu

Heated w/o cap on

Control

Heated w/cap on

Plastic “PET” Bottles

Uncapped Heated Plastic Bottle Observations

• Bottles are generally smaller– Height– Circumference– Volume– Exception area where cap is screwed on

• Gas Bubble appeared inside bottle.

Explanations

• Polymers are stretched when made into bottles – extruded using heat and pressure. When heated in the hot water those molecules of polyethylene-terephthalate or “PET” relax and so the bottle shrinks.

• The gas bubble is air that has come out of the water solution. Air is not as soluble in warmer water as colder water.

Discrepant events menu

Learning Patterns

• The class will be divided into two groups– Butterflies and Bluebirds

• Each group will be asked to do the exact same task after viewing some information for the same period of time.

• Prediction: One group will be significantly more successful than the other in completing the task.

154

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4 7

82

63 9=

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1 4

7

2 6

3 9

+

3

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4 7

82

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154

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9

Discrepant events menu

Mercury filled silver

Alcohol filled red

Generally there are two types of glass thermometers, alcohol and mercury filled.

Because of their hazardous affect on the human nervous system all Mercury thermometers have been removed from K-12 schools

Insoluble Solid/ Solvent Liquid

Soluble Solid/Solvent Liquid

Salt crystal - NaCl

Cl- Negative Chlorine ion

Na+ Positive Chlorine ion

Miscible

Immiscible

Liquid/Liquid

Liquid/Liquid

The calcium acetate, Ca(C2H3O2)2 is soluble in the water solvent

The calcium acetate, Ca(C2H3O2)2 is not soluble in the ethyl alcohol solvent.

When the alcohol is added it becomes the major solvent by volume.The calcium acetate precipitates out and forms a solid network.

The Sterno gel is formed.

Discrepant events menu

The Drinking Bird

Important Information

• Vapor Pressure– Is only affected by temperature changes

• Meaning if you reduce the volume occupied by a vapor of the liquid the vapor pressure will NOT increase. If you increase the volume occupied by a vapor of a liquid the pressure will NOT decrease. In both instances the vapor pressure will remain the same.

• You can not have a vapor pressure unless you have some of the liquid of the vapor present.

– The difference is that gas pressure is affect by both temperature changes, AND volume changes.

1. Water evaporates, cools head

2. Vapor pressure in head is lessened due to cooler (lower temperature) head. 3. Now the vapor pressure in butt is higher than vapor pressure in head.

4. Vapor pressure in butt pushes liquid up the tube. Center of gravity changes and bird dips

5. Bottom tube comes out of liquid, vapor pressure in head and butt is equalized, liquid returns to butt, bird rights itself again due center of gravity change.

The bird will not “drink” unless the head is dipped in water or some other liquid that readily evaporates. As long as the bird has access to the liquid it will continue to drink.

How could you make your bird into a dipsomaniac?

Dipsomaniac: An insatiable, often periodic craving for alcoholic beverages.

Discrepant events menu

Click for answer:

Hint: Use ethyl alcohol instead of water. It has a higher evaporation rate and cools the head more quickly as seen in the seminar. Try it and compare dip rate.

Methane Can

Getting the right mixture can be explosive.

 

                

The interaction of the three equal sides of the fire triangle: heat, fuel and oxygen, are required for the creation and maintenance of any fire. When there is not enough heat generated to sustain the process, when the fuel is exhausted, removed, or isolated, or when oxygen supply is limited, then a side of the triangle is broken and the fire is suppressed.

The Essentials Elements of Fire

Movie of Exploding Methane Can movie button upper left of page.

CH4(g) + 2 O2(g) --> CO2(g) + 2 H2O(g) methane oxygen carbon dioxide

water

gas gas gas gas

Reaction for Burning Methane Gas

From the balanced Equation

CH4(g) + 2 O2(g) --> CO2(g) + 2 H2O(g)

1 volume methane reacts with 2 volumes of oxygen

only 1/5 of air is oxygenTherefore

So the explosion occurs when the can is filled with 1 volume of methane to 10 volumes of air.

1 vol CH4 X 2 vol O2/1 vol CH4 X 5 vol air/1 vol O2 = 10 vol air

But

Discrepant events menu

Submerge Penny in water on a piece of aluminum foil for a minimum of 3 hours

Observe the aluminum foil after 3 hours to note changes if any.

Discrepant events menu

Note the holes, aluminum metal has been dissolved!

Wire screen top allows water to pour through. But when the jar is inverted the water’s surface tension and adhesive forces prevent water from pouring out.

Discrepant events menu

Supercool Sodium Acetate

• Potential Energy to Kinetic Energy

• Heat of Crystallization

• Energy in Energy out idea

• Physical Chain Reaction

Sodium Acetate Web Page

Discrepant events menu

Once your supersatured solution is made you simply store in it and use it year after year. All you have to do is heat it and let it cool slowly.

Making the original solution: The solubility of sodium acetate rises rapidly with temperature and, at 100°C, about 650g of CH3COONa will dissolve in 250ml of water. When the solution is slowly cooled without disturbance, the salt does not, however, re-precipitate and what is known as a supersaturated solution forms. Crystallization can, however, be induced by a the presence of a crystallization nucleus (crystal, glass rod, dust).

Movie of another demo

Mount Holyoke College ChemKit Program

• 1. Polymers: Children combine various concentrations of Polyvinyl Alcohol or “Elmer’s Glue All” and Sodium Borate to produce “ slime or silly putty type material”. They get to use laboratory equipment and scientific methods to explore the characteristics of polymers

Continued Mt Holyoke Kits

• 2. Acid/Bases: Included in the kit are different ways of testing for acidity. The students use pH meters, a natural indicator (red cabbage juice), and various indicator papers, including one they produce for themselves. A section on acid rain is included, as a natural link between the topic and the student’s own environment

Continued Mt Holyoke Kits

• 3. Percent sugar in chewing gum: Students are given a piece of gum to chew. Weights are taken initially and at different intervals. Students learn weighing techniques, data collection, and presentation, while exploring solubility and weight percents.

• 4. Crystals: Students from crystals from a supersaturated solution of sodium acetate. They observe a heat transfer as the crystals form. This kit contains a microscope and objective lenses, allowing the students to look at crystal structures.

Continued Mt Holyoke Kits

5. Rocks and Minerals: This kit was developed with the assistance of the

Mount Holyoke Geology department. It explores the hardness scale and the

crystal structures of rocks.

Continued Mt Holyoke Kits

6. Chromatography: Experiments using paper chromatography to extract and

separate dyes from black in pens, M&M’s and Skittles were developed. Students

learn about solvents, solutes, concentrations, dyes verses lakes, and

color separation.

Continued Mt Holyoke Kits

7. Dyes and Dying: This kit is an adaptation taken from our second semester organic

chemistry labs. Students use food coloring to dye a sample of test fabric.

They make predications, observe reactions to the dye on thirteen types of fabric, and draw conclusions when they

get unexpected results.

Continued Mt Holyoke Kits

Advanced Slime Lab: This lab requires the development of the correct combination of

polyvinyl alcohol with sodium borate to determine the best slime. This is for upper grades that want to discuss variables and

how to come to a conclusion as to which is the best slime. Introduces percentages and variables in science experiments.

Continued Mt Holyoke Kits

9. Projection of a marble: This lab has been developed by the physics department of Mount Holyoke College, for high school

physics lab. This lab involves velocity and ramps. Good lab for math and physics,

but it is high school level.

Requirements• The only requirement for borrowing any of these

kits is that the interested teacher must pick up and return the kits to the Chemistry department. The maximum time allowed to borrow them is two weeks. Since there is no charges with borrowing the kits, we do request that you return them within that two week period so that we can restock them for others. To borrow one of these kits please contact Edward Fitzgerald at 413-538-2398.

• ECF/2006