Weird Science: Investigate It

There’s a mystery afoot at the library! Every morning the library staff comes in to discover misplaced books, chairs that have been moved, and some cookie crumbs. They have some suspects, but haven’t been able to solve the mystery yet. Can you help?

You’ll Need:  Grape Juice  Cups  Paintbrush  Spoon  Paper  Warm Water  Pencil  Baking Soda  Tape

Fortunately for you, detective, our mysterious midnight-reading book culprit is a little messy. They always leave books and cookie crumbs around (they must like a midnight snack). They’ve also left behind two key pieces of evidence that we think will help you catch the culprit!

But first, let’s introduce you to the suspects. . . .

Suspect #1: Library Ghost  Reading Interests: History, Haunting 101, & Mysteries

Suspect #2: Wizard  Reading Interests: Magic, Wand DIYs, & Firework Science

Suspect #3: Page the Pelican  Reading Interests: Fiction, How to Fish, Visiting Lakes & Rivers

Suspect #4: Fairy  Reading Interests: Fairytales, Teeth & Dental Hygiene, Flight & Fashion

Suspect #5: Gnome  Reading Interests: Gardening, Tiny House DIYS, & Mushroom Identification

Clue 1: Invisible Ink One morning we discovered a piece of paper on the floor by a chair. It appears to be blank, but any good investigator knows there’s more to something than meets the eye! We’re pretty sure our scrap of paper might hold an invisible ink message. We need your help to reveal it! First, let’s mix up some invisible ink and a reagent of our own!

1. In a cup, mix together equal parts baking soda and warm water. Stir, stir, STIR until the baking soda is (mostly) dissolved. You’ll still have some grainy bits. This is your ink! 2. Using a Q-tip or paintbrush write your message using the baking soda solution on a blank piece of paper. It’s best to dip your writing tool all the way to the bottom of the cup. Your ink should appear nearly invisible! 3. Set aside your paper to dry completely. 4. Once dry take a look at the paper. Do you notice the invisible ink? Are you able to read it? Can you feel it or smell it? Invisible inks are revealed using something called a “reagent.” Our reagent is grape juice! Paint over your message (or a friend’s) using grape juice.

What happened? The grape juice should have revealed the hidden message!

Invisible inks harness the power of chemistry! When our two substances combine they create a chemical reaction. Invisible inks that rely on a reagent and chemical reaction to be revealed (instead of heat or a light source) are called sympathetic inks! In the case of our chemical reaction our baking soda is part of a chemical group called“ bases” when mixed with an item from the chemical group “acids” (like our grape juice) a chemical reaction occurs! You have probably seen the same power at work if you’ve ever mixed baking soda and vinegar!

Now let’s put our new skills to use solving the mystery! If you picked up a library kit, open Envelope #1. What’s inside? Can you reveal any invisible ink on the clue paper? Hmmm….let’s save this information and see if it will be useful later!

FUN FACT: Invisible ink has been used for over 2,000 years! Clue 2:

The second clue we discovered was a left behind on a book! That was very careless of our culprit, because fingerprints are keys—they are totally unique to you! No two people in the world have the same fingerprint (even identical twins)! Let’s practice examining and lifting fingerprints.

1. Take a look at your fingers. Are you able to see your fingerprints? What do you notice? 2. Take your pencil and on a blank sheet of paper scribble as HARD as you can in one small section of the paper. You want a really black square of pencil on that paper! 3. Press a finger down HARD in the pencil scribble area on your paper (it’s easiest to start with your thumb or pointer finger). Roll your finger to each side. If you pick your finger up you should have pencil all over it! Take a careful look. Is it easier to see your fingerprint now? 4. Carefully get a piece of tape. Try to touch as little of the tape as possible! Be careful and hold it on the corner. Put the sticky side of the tape on the pencil covered finger. Press it on HARD. 5. Now, we’ll lift the fingerprint! Carefully peel the tape off and stick it on a blank sheet of paper. Now you can examine your fingerprint! Although everyone has different patterns, there are some common fingerprint elements. Use the chart below to identify the elements you can find in your fingerprint. If you’d like compare the fingerprints from each of your fingers!

Here’s some cool facts about fingerprints:  They form before you’re born  They are more unique than your DNA (the building blocks of your cells and body!)  They stay the same your whole life!  You leave them behind on anything you touch! (The oil and dirt on your hands makes this possible. You can see this by putting a piece of tape on a clean finger and peeling it off or holding a clean glass and looking carefully once you take your fingers off).

Now let’s put our new skills to use solving the mystery! If you picked up a library kit, open Envelope #2. Seems like our culprit left a fingerprint behind! We should easily be able to identify them now!

Accusations You’ve had a chance to examine two clues left behind by the culprit. Take some time to examine what you’ve discovered.

Does your first clue, the invisible ink note, rule out any suspects? Does the fact that there’s a fingerprint rule out any suspects? Were you able to match the evidence fingerprint to any of the suspects?

Once you have an accusation open Envelope #3 to see if you are correct!

Well done today, detective! .