Category: science projects

Invisible Ink Messages (“Messages” Unplugged Project)

By , January 23, 2011 4:00 pm

All spies love invisible ink.  In honor of this month’s Unplugged Project theme of messages here are two simple methods for making secret, invisible ink messages out of ordinary ingredients.

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LEMON JUICE:

Either squeeze a lemon or be lazy like me and use that store bought lemon juice that comes in the little plastic lemon!  Put the juice in a small dish and use a cotton swab to write your secret message.

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BAKING SODA & WATER:

Mix together equal parts baking soda and water in a small bowl.  Again, use a cotton swab to create your message.

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Once the messages are completely dry and can no longer be seen on the paper, hold the paper over a heat source and the message will magically be revealed to guaranteed “oohs and aahs!”  (Obviously an adult should complete this step, especially with young children, so as to avoid burns and flaming paper.)

By the way, we found that the baking soda produced a slightly darker result than the lemon juice.

NOTE:

For those whose children channel James Bond rather than Martha Stewart, a high-tech invisible ink spy pen complete with built-in ultraviolet decoding light might be just the ticket. My son found this one in his Christmas stocking:

LINKS – More about invisible ink:
The Naked Scientist – Secret Messages-What Makes an Invisible Ink?
Kidzworld-How Invisible Ink Works
Science Project Ideas – Invisible Ink (this site has some other interesting methods too)

Secret Codes: The Cardan Grille (“Messages” Unplugged Project)

By , January 10, 2011 2:39 pm


My two oldest children are really into secret codes at the moment and when I asked them for suggestions for this month’s Unplugged Project theme, my 8 year-old son immediately said “Messages! We could make codes!”

So here is our first code, a version of the famous code known as the Cardan Grille.  For this code, a special template is used to encode and decode a message. Here’s how we made ours:

You’ll need paper (graph paper makes it much easier), a sharp pencil, scissors, a ruler, and a box cutter or razor blade.

First mark out evenly spaced boxes on your graph paper.  You will be cutting some of these into square openings, so you’ll have to leave some blank space around each box.  (Our boxes were two graph squares wide and two squares tall with one blank square between rows.)

First we marked off rows of squares then we drew the grid using the ruler.

Next we laminated our paper.  If you don’t have a laminator, you might want to paste it to some stiff cardboard or posterboard just to make it tougher.  If the grid gets lost or destroyed, no one can crack the code and you will be fired as a secret agent!

I used a box cutter to cut random squares out of the grid.  I put an old wooden clipboard underneath in order to avoid damaging the desk.  You could use pointy scissors for this step, but a razor-type blade makes the job much easier. (Obviously, an adult should do this step.)

The finished template (with my “helpers” in the background):

Now you are ready to encode.  Place the template over a fresh sheet of paper.  Mark around the corners with a pen to make it easier for the decoding person to line it up.  Write your message (one letter goes in each square).

Remove the template and fill in all the open squares with random letters.  Can you figure out what this says?

Here is the solution:

(“The girls are hiding the treehouse.” – OK, so it was supposed to say “The girls are hiding in the treehouse but we forgot the “in.” But coded messages are supposed to be brief, right?)

NOTES:

  • You can make your template as big or as small as you like.
  • For ease of communication between spies, you really ought to make a duplicate template so both sender and recipient have their own.  Just place the first template over a new piece of paper, trace the locations of the squares, laminate, and cut out.
  • I numbered the corners of the template 1 – 8 because you could use both sides and all four orientations to create different messages, or even one long one.
  • Traditionally, the template was placed over an ordinary letter (see the example here) but it can be very challenging to come up with a natural sounding message built around the coded text.  I gave it a try though and it was a fun mental exercise:

(“Arrival at six PM.”)

Watch the Perseid Meteors Tonight

By , August 14, 2010 2:53 pm

perseid_meteor_2007

By Brocken Inaglory – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2632873

Last night I woke my two oldest children up at 2:30AM.  I led my confused and sleepy babies out onto the golf course behind our house armed with a flashlight and a blanket.  I spread out the blanket on the cool, damp grass of the fairway, we all laid on it facing northeast … and hoped that the sprinklers would not go off! Lol!

The children were astonished by what they saw – shooting stars, lots of them!  We also saw the Milky Way and several satellites marching in line across the night sky.

Our fabulous unplugged (and free!) show was the annual Perseid Meteor Shower.  The peak was the nights of August 12 and 13th, but you might still be able to see a pretty good display through the 22nd (especially if you are lucky enough to live in a low ambient light area like we do).  Just look to the northeast after midnight.

PS.  Most visible in the Northern Hemisphere, sorry!

LINKS:

EarthSky’s Meteor Shower Guide

Excellent Perseid Meteor Shower Expected

How-To: Photographing the Perseid Meteor Shower

Perseid Photo Gallery

For another of our astronomy adventures, you might like to read: The Moon Unplugged? Not For Me!! (Part 1) and Mom Unplugged vs. Evil Sleepy Poser Mom – Lunar Dilemma Part 2.

Nice Day + Old Fish Tank = Terrarium

By , May 20, 2010 3:41 pm

Are you without any ideas for organized unplugged things to to do on a nice Spring day but you aren’t feeling ambitious enough for a full blown Children’s Garden?  Do you have an old fish tank, or large glass bowl?  See if your kids want to make a terrarium!

Very few children can resist the idea of their own tiny little garden.  Even I remember making one and being totally fascinated by the magic of such a small scale.  To me it was like a little doll house garden.  If you have a fairy-lover, call it a Fairy Garden.  A dragon-lover, why not make a Baby Dragon Garden!  Be creative.

Last Sunday when we had our first gorgeous spring day, I finally told my 9 year-old that she could have the old fish tank in our garage that had been gathering dust in our garage for at least 6 months.  She has had her eye on it for some time – but for me, snow and cold are not conducive to warm, green creativity.

We finally pulled it out and I told her she was on her own.

This is what she came up with all by herself (as long as you don’t count my driving her to the nursery to get her plants while I bought mine).

I LOVE the reuse of the little fairy house from our fairy garden of 2 years ago and the path of rocks that lead to it.  There is even a pond made out of a food storage container that my daughter wants to put tadpoles in.  She put some sea shells in the pond and broken terracotta pots as homes for the future frog residents.  Some of the ferns look like trees and there is a small sprig of English Ivy for which she plans to make her own twig trellis.

Very fun and easy!

– Teaches kids not only to be creative about their landscaping ideas, but responsibility in caring for their creation.

– If you don’t have a suitable glass container, try searching yard sales and thrift stores.

Make a Salad Spinner Zoetrope

By , October 16, 2009 5:03 pm

zoetrope

The theme for this week’s Unplugged Project was wheel.  I searched around for ideas and came up with this one which sounded really interesting:  a zoetrope!

What is a zoetrope you ask?  (I didn’t know what it was either.)  A zoetrope works on the same principle as a flipbook, one of those little books where you flip the pages and it looks like an image is moving, but it uses a rotating cylinder to produce the illusion of movement.

I like this definition from Wikipedia:  “A zoetrope is a device that produces an illusion of action from a rapid succession of static pictures.”  The word zoetrope comes from the Greek zoe (life) and trope (turn), so it is really a “wheel of life,” perfect for our theme!

I found instructions for making a zoetrope many different ways:  using a round camembert cheese box, a PVC pipe, a straw and a printout, a paper plate, and ice cream containers.  We originally made up our own version out of black poster board, an old CD, a small lazy susan, and lots of tape.  It was OK, but a bit wobbly.

Then I found a totally ingenious person who made one out of a salad spinner!  Why didn’t I think of that?  We absolutely had to try it and the result was AWESOME!  It is an easy project that produces a maximum “wow factor.”  Try it, here’s how:

Use electrical tape to tape off the slits on the salad spinner basket leaving every third slit open. We used 3/4″ electrical tape and that just happened to be exactly the right size for the job.

For images, the salad spinner genius used cutouts of the phases of the moon from a calendar.  Very clever but I decided to draw my own pictures.

On a piece of white paper I marked off a series of 3/4″ x 3/4″ squares.

Then, using a black Sharpie, I drew a face with a changing mouth and waving hair, making each image slightly different than the previous one.

The tedious part was cutting out all 26 images and taping them in sequence to the blocked off areas of the inside of the salad spinner.

Finally, using a clump of rolled up tape, stick your zoetrope onto the overturned lid of the salad spinner, centering it as best you can. The zoetrope will be sitting on the rotating disk, and the salad spinner handle will be underneath.

Now for the fun: spin and look through the slots to see the “movie!” The view is best if you shine a bright light into the bowl of the zoetrope.

Hopefully you’ll see from this little 10 second video that we made, how cool this project really was!

Let’s not forget THE SCIENCE:

So how do flipbooks, zoetropes, thaumatropes (a rotating card with a different picture on each side, the pictures appear to combine when card is spun), cartoons, and old time film movies actually work?  Many people still believe in the “persistence of vision” theory, in which it is thought that an image remains in the eye for a certain time after the image source is actually gone (ie. the optic nerve is the cause).  Apparently that theory is no longer in favor these days.  A more popular theory at the moment involves something called Beta movement where the brain itself apparently combines rapidly flashing images thus forming a perception of movement (ie. the brain is the cause).  It seems that no one really understands any of this completely.

FIELD TRIP:

You can visit a real zoetrope at the following museums:

V&A Museum of Childhood, London, UK

The Ghibli Museum, Tokyo, Japan

Great Lakes Science Center, Cleveland, Ohio, USA

Headwaters Science Center, Bemidji, MN, USA

Have fun!

(Be sure to visit the links to other people’s wheel Unplugged Projects on last Monday’s Weekly Unplugged Project post.)

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