Stem Seminar Discrepant Events Peter Shaughnessy March 2007 Note: click the bird to get back here. E-mail contact (if you have a question please ask it) email@example.com
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 Menu Demonstrations List Patterns and Learning Plastic Bottles Penny Eats Metal Flashy Solid Jarring Surface Tension Supercool Liquid Releases Heat Drinking Bird Methane Can Activities List
Activities 7 Taping the Charge 1 Vanilla Balloon 8 Polar Water 2 Alcohol and Water 3 Hot and Cold Water 9 Non Polar - Polar 10 Probing Water 4 Rates of Evaporation 5 Feeling Your Alcohol 11 Heavy Metal Tension 6 Water Mosh Pit 12 Reaction Rates Discrepant Events
Adding Vanilla to Balloon Vanilla liquid begins to evaporate and form a gas.
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 Gases Rotational Movement Gases, Liquids Vibrational Movement Gases, Liquids, Solids
5 sec 15 sec 35 sec 25 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 Kinetic Energy Intermolecular Attractions Relative Humidity Dynamic Equilibrium Activity Menu
Temperature Scales oC = Celsius oF = Fahrenheit Space inside thermometer above the alcohol is a vacuum meaning there is nothing there! 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 Alcohol filled bulb
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.
7 Taping the Charge Atoms 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 Like Charges Repel Negative repels Negative Positive repels Positive Electrons can be removed from atoms by rubbing or touching. Opposite Charges Attract Positive attracts Negative Negative attracts Positive Activity 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
+ + H H O =
Hydrogen Bond Between Molecules Only
Briefly Hydrogen Bonds in Water are Responsible for: High Surface Tension of water High Boiling Point of water High Freezing Point 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.
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 reaction Aspirin, Sodium Bicarbonate, and Citric Acid Activity Menu
Plastic “PET” Bottles Heated w/o cap on Control Heated w/cap on
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.
1 2 3 6 4 5 9 7 8
1 4 7 = = = 2 8 5 = = = 6 9 3 = = =
2 6 3 1 + 3 4 3 9 7
1 4 7 = = = 2 8 5 = = = 6 9 3 = = =
1 2 3 6 4 5 9 7 8 Discrepant events menu
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 Alcohol filled red Mercury filled silver
Insoluble Solid/ Solvent Liquid Soluble Solid/Solvent Liquid
Salt crystal - NaCl Cl- Negative Chlorine ion Na+ Positive Chlorine ion
Liquid/Liquid Liquid/Liquid Immiscible Miscible