powder mystery

Powder Mystery – Lesson

Many real life samples do not come carefully packaged and labelled.  So how do we find out what they are?  Who could possibly do that?

Science to the rescue!!!  Well, specifically, comparative analysis to the rescue.

In this mini-lesson we will

  • Explore different properties of our sample powders
  • Practice a little lab safety
  • Record observations
  • Identify mystery powders by comparing them to what we already know!

Time to Complete

5 minutes prep, 15+ minute lesson

Concepts

Comparative analysis

Vocabulary

Comparative analysis, wafting, control sample, acid, base

Supplies

  • Powder Analysis sheet –  1 per child
  • Cream of tartar – 1 teaspoon
  • Cornstarch –  1 teaspoon
  • Baking soda –  3/4 teaspoon
  • Vinegar  about – 1 Tablespoon
  • Iodine  about – 1 Tablespoon
  • Ice cube tray  – 1
  • Black or dark construction paper  – 1
  • Small bowls or containers  – 2
  • Pipette or syringe
  • Magnifying glass (optional)

Iodine is available in the first aid section of most stores. If you have iodine already for first aid use, do not dip a pipette or syringe directly into the bottle. You do not want to contaminate your first aid supply.

Preparation

Sample testing

powder sample prep
  • Prepare labels for your testing.  You will need 3 each of cream of tartar, cornstarch, and baking powder.
  • Place 1 label in each space in a ice cube tray.
  • Add  1/4 teaspoon of the powder to the ice cube tray according to your labels

Mystery samples

  • Place 1/4 teaspoon of cream of tartar into a separate small bowl or container as a Mystery Sample #1.
  • Place 1/4 teaspoon of cornstarch into a separate small bowl or container as a Mystery Sample #2.

Lesson

This is the general lesson format.  Please refer to “The Science” section for more information on what science to teach during the lesson.  That section is provided separately so you can pick and choose what is most interesting and appropriate for your learners.

What is that?

In real life, you just don’t know what will get handed to your for testing.  Especially in a crime scene.  A mysterious white powder, a smudgy-gooey something, a unraveled fiber from who knows what…

Where do you even start?  Well, luckily for us, experimentation will help us identify that unknown whatsit!  By comparing something we know and have tested with something unknown, we can identify that unknown.

This process is called comparative analysis.  Analysis is a thorough study of something to understand it better.  So comparative analysis means you study something then compare it to other samples that you have already analyzed to see if they are the same.

Take a look

Now lets have a look at our test powders!  We are testing salt, sugar, cornstarch, and baking soda.  Look closely at each powder.  Are some fine (small pieces) and other course (bigger pieces)?  Is one shinier than another?

This will be easier by putting some of each of the powders on black construction paper.  You can also use magnifying glasses if you have them.

Fill out the Powder Analysis Sheet about what you find.

Feel it

Take a bit of each sample and rub it between your fingers.  How does it feel?

Fill out the Powder Analysis Sheet about what you find.

LAB SAFETY TIP In a real forensic or police lab, you would NEVER handle samples with your fingers. Always using gloves. But this is just us testing some at home powders so bare hands are alright.

Smell it

Now for smelling our samples!  These powders don’t really have a potent smell but it will be a good chance for the kids to practice describing their senses.

Fill out the Powder Analysis Sheet about what you find.

LAB SAFETY TIP NEVER, NEVER, NEVER put your nose directly over a chemical to smell it! Many gases can harm your nose or even be deadly. Always use the technique of wafting. That means you scoop the air above your sample container toward your nose so you can get the scent, but not too strongly. It’s never too young to start teaching lab safety!

It’s reactive!

Our last tests are for chemical reactions.  When you add different liquids to the powders so of them are doing to do funny things!  Lets test it out.

Water

Plain ‘ol water.  Add 4-6 drops of water to the 1st sample of each powder.  What do they do?  This is the control for our analysis.  A control is a “normal” sample.  When we add other liquids to the powders, we know that the change is taking place because we added iodine or vinegar and it would not do that with just any liquid.

Vinegar

Add 4-6 drops of vinegar to the 2nd sample of each powder.  What do they do?  The only powder that should react is the baking soda.  It will bubble up when the vinegar is added.

Iodine

**Parents should help with the iodine because it will stain!

Add 4-6 drops of iodine to the 3rd sample of each powder.  What do they do?  All of them will be darker because of the red/brown color of the iodine.  But the cornstarch will turn a dark blue/black.  The iodine has reacted with the starch to form something completely new!

Fill out the Powder Analysis Sheet about what you find about each powder and liquid.

powder testing example

Solve the mystery!

Allow the kids time to test the 2 mystery powders in the same way as the previous samples:  look, touch, smell, and test with water, vinegar, and iodine.

Fill out the Powder Analysis Sheet about what you find.

How well did the analysis go?  Did you identify the mystery powders?

Take a look at real life

A crime lab can seem like a different world for a kid.  So lets think about this testing a little closer to home:

I have put my baking soda and my cornstarch in identical containers in the cupboard.  But I forgot to label them!!

How can I test to know which container is which?  What other ways could these tests be helpful?

There so much extra on the PDF!

Our lesson plan PDF is just chock full of good stuff that is too much to put here.  Grab the full lesson plan to get “The Science” section, vocabulary,  and the Powder Analysis sheet.


This activity is part of Who Stole the Cake? [Unit 2].  Jump over to the unit main page to see all lessons and activities.

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