CAN’T JUDGE A POWDER(B)

By Lin Wozniewskilwoz@iun.eduJamie Cucinottajamiecucinotta@me.com

SAFETY

Students must wear: Closed shoes Slacks or skirts that come to the ankles Lab coat or lab apron Indirect vent or unvented chemical splash

proof goggles. No impact glasses or visorgogs are permitted

Long-Sleeved Shirt (if wearing a lab apron) Long hair (shoulder length or longer) must

be tied back.

THIS IS NEW…

Long hair, shoulder length or longer, must be tied back.

GOGGLES: MUST BRING

Goggles: ANSIZ87

NOT THIS KIND

STUDENTS MUST WEAR AN APRON

WHAT STUDENTS MAY BRING

Their kit. Please check and make sure kids have packed everything they will need.

NO writing utensils. These will be given to them.

They are given one color pen/pencil for their data and another for recording their answers.

WHAT STUDENTS CAN BRING

test tubes & racks, spot plates, well plates, reaction plates, beakers or similar small containers for mixing

something for scooping & stirring pH or Hydrion paper hand lens(es) Beral pipettes 9-Volt or less Conductivity tester paper towels Test tube brush

WHAT STUDENTS CAN’T BRING

Reference Materials Calculators Writing instruments of any kind ANY materials other than on previous

slide

Ranking below those who have followed the rules

The Penalty?

CONDUCTIVITY METERS

Do not have to be fancy or expensive but can be

WHAT SUPERVISORS WILL PROVIDE 1 Substance 1 M HCl 1 M NaOH 2 Different writing instruments Waste Container Wash bottle of Distilled Water (ROI) Instructions about whether refills of the

powder are allowed Instructions on how to use probes or

extra reagents

WHAT NEW??

Any additional equipment or reagents given to the students

So, other equipment will have instructions unless the object is simple.

Ex: a magnifying glass would not have instructions.

Flame loop and Bunsen burner would come with instructions (not happening at States!)

WHAT SUPERVISORS MAY PROVIDE

Thermometer or temperature probes Balance Hot plate Anything else the supervisor decides

to distribute. If the supervisor feels instructions are needed in order to use something provided, the instructions will be available

SUBSTANCES THAT COULD BE GIVEN BY THE JUDGE

Phenolphthalein Hot plate Thermometer Benedict’s

solution Silver nitrate Magnet

Magnifying lens Iodine Beaker with

boiling water Universal

Indicator balance

MAIN FOCUS

Observations The distinction between an observation

and an inference How to prepare students Scoring the Exam Resources

OBSERVATIONS

Emphasize to students that the purpose of this lab is NOT to identify the powder. (That is the Science Crime Buster event-not this one)

The purpose is to characterize the powder!

This event hits all of the Middle School National Physical Science Standards.

Therefore it is an excellent event to actually use in the classroom to teach observation and the difference between observation and inference

OBSERVATIONS

Students need to learn to write down observations, not inferences.

Students need to be as specific as possible. While both flour & cornstarch might at first

glance be described as “white powders”, flour is generally more of an ivory white or creamy white, whereas cornstarch is more bright white

Students need to be encouraged to write observations as sentences including what was being observed as well as what was observed.

OBSERVATIONS

Students should do tests on the reagents they are given as well as the powder. If you do not know for sure if the liquid you

are attempting to dissolved the solid in does or does not conduct electricity, you can not say for sure what the solid did

If you do not know what the temperature of the liquid was before you start dissolving, you can not know by how much the temperature changed.

OBSERVATION & INFERENCE If the student attempts to dissolve the .1g

of the powder in 1 ml of water and the temperature goes down from 22.1C to 20.9C, that is an observation

If instead the student writes down that dissolving the powder is an endothermic process, that is an inference.

You would use the first observation to answer the question of whether or not the dissolving is exothermic or endothermic.

But you would get less points for answer 2

OBSERVATION VS. INFERENCE-WHAT’S THE DIFFERENCE

Observations are things that you use your five senses to discern. (No-you are not allowed to taste or touch anything in this lab!)

Inferences are anything that does not use your senses to discern. So you can see a thermometer and observe

a temperature or a temperature change. But you have to infer that the act of

dissolving then takes in or gives off heat based on your observation of the temperature going up or down.

TYPE OF STUDENTS TO TRAIN

Students who are careful. Observant Good penmanship Students who clean up after

themselves. Students who work well together, yet

can work independently.

Students should work quickly and get as much data as they can.

They may have 25-35 minutes for Part I and about 20 minutes for Part 2.

HOW TO PREPARE STUDENTS Have students start by observing powders

and reagents and doing sample tests Students need to make the observations on the

reagents first, and then the same observations on the solutions (if any)

Students need to make observations with any “extra” reagents or equipment the event supervisor gives

Students need to get out of the habit of trying to answer the question. They put the observation number as the answer

Coach or assistant scores test and goes over results with students

HOW TO PREPARE STUDENTS

Have students get out powders and make up tests for each other Students score tests themselves This event is very much like Write-It, Do-It.

Students will get unbelievably better if they have to make up questions and score results.

QUESTIONS

The questions the event supervisor is likely to ask can be divided into two main categories: “Standard Questions”

What color is the powder? Is it a powder or a crystal or a granule Etc

“Powder specific questions” You can not ask if dissolving the powder in

water is exothermic if the powder is insoluble in water.

Etc.

CLEAN UP

Have students pack some paper towels to clean up their mess.

If they use a plastic tub/kit they can just throw everything in there and clean up later.

Points are deducted for leaving a mess. This happened even at Nationals.

DIFFERENCE BETWEEN OBSERVATION AND INFERENCE

In the data they can say “the temperature went from 12oC to 15oC”.

They cannot say the solution was “exothermic”.

GRADING

Students get up to 5 points for having the correct data to answer the question.

They can get up to 2 points for no data, but knowing the correct answer.

SOME OBSERVATIONS STUDENTS COULD MAKE

Color of powder Crystal shape Hardness of crystals Solubility-make sure they don’t take too

much Density of solid Take pH of water before adding anything pH of powder in solution (kids often do this

after adding NaOH or HCl)

Conductivity of the solution Place a small amount to the side and

make an observation after 20min or so if the solid has absorbed water.

Color of the solution before adding any other chemicals.

Be sure to use all the reagents given. The color of the precipitate should be

noted.

Make sure students do not hold on to test tube when making temperature measurements.

Take temperature of water before adding the powder.

Test the gas given off: Wet pH paper and hold it over the gas Be sure to not touch the sides of the test

tube The ammonia gas will turn dark blue

Know if the substance is ionic or covalent based on data recorded.

Be sure students take the mass of the powder if a balance is available.

Note the odor Note the luster

Bonus Questions:-Could be to balance an equation-recognize an acid or a base-know the symbols for simple/common elements

RESOURCES

For Event Supervisors http://mypage.iu.edu/~lwoz/socrime/index.

htm For Lesson Plans for classroom use

http://mypage.iu.edu/~lwoz/socrime/index.htm