CWU – Chemistry and Sci-Ed – Tim Sorey, PhD. A Mini-Inquiry – Milk, Dye, and Soap
A Mini-Inquiry (1) – Milk, Dye, and Soap INITIAL OBSERVATIONS – (Work in teams of 2 or 3 people.) (Wear Goggles, please.) Procedure Observations 1) Fill petri dish ½ full of 2% milk. 1) 2) Place a single drop of food 2) Coloring (red) in the middle of the 2% milk. 3) Within 15 seconds, place a drop of soap in the center of the food 3) ?????? coloring.
A Mini-Inquiry (2) – Milk, Dye, and Soap Question: Does milkfat play a role in the speed of the observed chemical reaction? Prediction: Increasing milkfat will cause the observed chemical reaction to speed up. Repeat the previous procedure with Skim Milk, Whole Milk, and Half-and-Half Milk. What did your team find out? What do your collective data suggest? Do you all agree with one another? Let’s do this together on the overhead projector! WHAT ABOUT A SCIENTIFIC HYPOTHESES?
The Hypothetico-Deductive Method The so-called hypothetico-deductive method of science is a term that some have misconceived as a scientific educated GUESS followed by confirming or denying its validity through quantitative data, only. NOT THE CASE! Probably the most important part of this ‘old school’ dogma is the EDUCATED guess. “EDUCATED” presumes that prior knowledge or experience has preceded the guess. Also, either qualitative and/or quantitative data are adequate for analysis of the “guess”. An acceptable “FORMULA” for an HYPOTHESIS: 1) Know what you are trying to study with no less than ONE previous experiment or activity with the provided materials. 2) Know what you are manipulating (x), what you believe is responding (y), and follow this with a reasonable scientific explanation of WHY this may be the case. Hypothesis = (If a manipulated variable is ‘tweaked’ then a responding variable (y) will react) + (because of a plausible scientific explanation) “If__(x)_____then__(y)____because__(scientific explanation)__.”
A Mini-Inquiry (3) – Milk, Dye, and Soap Identified Variables: Milkfat = Manipulated Variable (Independent Variable) (x) Speed of Reaction = Responding Variable (Dependent Variable) (y) Hypothesis: If milkfat increases then the speed of the initial reaction will increase because soap is used to “cut through” fats and greases.
A Mini-Inquiry (4) – Milk, Dye, and Soap Hypotheses are difficult to construct and they take quite a lot of practice. For K-8th Grade, students should be able to inquire by asking scientifically testable questions and formulating scientific questions. Scientific Question: A scientifically testable question. Scientific Prediction: Stating an educated inference and taking a stand on how you believe the idea or question will turn out after collecting data. (Staking a claim.)
A Mini-Inquiry (5) – Milk, Dye, and Soap What about YOUR OWN inquiries? • Change a single variable • Ask a different testable question • Create a Hypothesis • Make a prediction • Run a few experiments to test your question • Discuss your results • Did you answer your questions….(CONCLUSION!) • Did you have OTHER questions? RESEARCH = Search + Search + Search for the best possible answer to your question
A Mini-Inquiry (6) – Milk, Dye, and Soap Explanation of Soap interacting with WATER and OIL! Go to OVERHEAD and enjoy the DEMONSTRATION and HAND-OUTS! Bubbles….what’s up with that?
A 5 step Learning Cycle A model forTeaching– K-8th grades • 5 stage model: • Safety • Create a physically safe learning environment • Engage • Create interest/curiosity, raise questions • HOW? – INITIAL MILK EXPERIMENT • Explore • Student explore with intermittent teacher facilitation • HOW? – Teacher-Based Inquiry using %milkfat as a focus QUESTION • Explain • Students/Teacher discuss concepts and experiences • HOW ? – DEMO that displays miscibility and like dissolves like • Extend • Apply developed concepts/skills toward a new experiemnt • HOW? – Student-Based Inquiries using other materials. • Evaluate • Ongoing process, teacher- and student-based • HOW? – Journaling, Worksheets, Questioning, Discussing….etc.
Fats, Oils, and Greeses Saturated Fats/Oils/Greases - HydroCarbons Unsaturated Fats/Oils/Greases - Hydrocarbons H H H H H H H H C C C C H H C C C H H H H H H H H H H H H H C C C C H H C C C H H H H H
Science Content in the Food Chemistry Kit (2) • Sugars – WHAT ARE THEY? • Sugar - a water soluble mixture of “sugars” C6H12 O6 • Fructose (monosaccharide) • Glucose (monosaccharide) • Sucrose (disaccharide) • Page 58 of manual – sugar sources • Cornstarch? – Alarge molecule with repeating structural units…
Corn Starch – Something Special! • Corn Starch is a large molecule of repeating structural units or POLYMER. • If you look closely, you can see a pattern…what is repeating? • HINT: C6H11O5 - (C6H11O5)x - C6H11O6 Where x is a VERY LARGE number! ***Corn Starch is a POLYsaccharide***
Iodine Indicator • What properties of starch (given its chemical structure) allow it to be used as an indicator? DavenderKhera, Yale University • When starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. Many of the details of the reaction are still unknown. But it seems that the iodine (in the form of I5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a soluble starch). The starch forces the iodine atoms into a linear arrangement in the central groove of the amylose coil. There is some transfer of charge between the starch and the iodine. That changes the way electrons are confined, and so, changes spacing of the energy levels. The iodine/starch complex has energy level spacings that are just so for absorbing visible light- giving the complex its intense blue color. The complex is very useful for indicating redox titrations that involve iodine because the color change is very sharp. It can also be used as a general redox indicator: when there is excess oxidizing agent, the complex is blue; when there is excess reducing agent, the I5- breaks up into iodine and iodide and the color disappears. Author: Fred Senesesenese@antoine.frostburg.edu • Reduction/oxidation Reaction or REDOX RXN – Electrons are exchanged and chemical bonds are rearranged (both broken and formed) • Oxidation is LOSS of electrons • Reduction is GAIN of electrons • OIL RIG
Coomassie Blue – Test for Proteins • Coomassie Blue is an organic molecule that is used to stain proteins. Remember that “LIKE DISSOLVES LIKE”. • The original Coomassie dye was developed as a wool dye and named to commemorate the 1896 British occupation of Coommassie (now Kumasi) in Ghana. • Proteins, also known as polypeptides, can bond to one another in acid-base pair combinations called “PEPTIDE BONDS”. These AMINO ACIDS are the basic building blocks of life. • Scientists have found many different amino acids in protein, but 22 of them are very important to human health. • Of those 22 amino acids, your body can make 13 • You can figure out how much protein you need if you know how much you weigh. Each day, kids need to eat about 0.5 grams of protein for every pound (0.5 kilograms) they weigh. That's a gram for every 2 pounds (1 kilogram) you weigh. Your protein needs will grow as you get bigger, but then they will level off when you reach adult size. Adults, for instance, need about 60 grams per day. http://kidshealth.org/kid/stay_healthy/food/protein.html Coomassie Blue Protein Pairs
Glucose Test Strips – How do they work and why sometimes they don’t? • Usually due to one or more REDOX reactions that change colors due to the presence of a particular compound. • These strips are specific to glucose. You will not get a reaction with soft drinks or regular sugar since these are mainly fructose or sucrose. However, one simple demonstration anyone can do is to chew a saltine (salty cracker) and spit out a bit after a few seconds & test it. Then try it again but chew longer so that the salty taste disappears and begins to taste slightly sweet. The strips are sensitive enough to detect this. • The glucose test strips are intended for demonstrating osmosis across a membrane similar to the way the small intestine works. One can show that starch does not cross the barrier but glucose does. The color test chart indicates concentration levels in mg/dL but you can convert this to mmol/L by multiplying by 0.055. eg. 100mg/dL is equal to 5.5mmol/L. OTHER TESTING REAGENTS for SUGARS! • Benedict's reagent is used as a test for the presence of all monosaccharides. These include glucose, galactose, mannose, lactose, and maltose. Even more generally, Benedict's test will detect the presence of aldehydes (except aromatic ones), and alpha-hydroxy-ketyones. Benedict's reagent contains blue copper(II) ions (Cu2+) which are reduced to red copper(I) (Cu+).
pH factoids and pH Indicators • pH is the measure of acidity or H+ and OH- ions in water (H2O) • At 25oC water has a pH scale from a range of 0.0 to 14.0 • pH>7 is basic • pH < 7 is acidic • pH = 7 is neutral http://www.erowid.org/archive/rhodium/chemistry/equipment/pictures/ph-cabbage.jpg
Baking Soda and Vinegar • Classic Reaction…what’s going on? • Baking soda (HCO3-) and acid(H+) decompose to create two new compounds, carbon dioxide gas(CO2) and water(H2O). HCO3- (aq)+ H+(aq) CO2(g) + H2O(l)
Contact Information • Timothy L. Sorey, PhD. • Central Washington University • Department of Chemistry • Department of Science Education • email@example.com • 1-509-963-814