Mini Monday: Lever Launcher

Hello girls!  I hope all of you in the USA had a great Thanksgiving!  For this week's Mini Monday, we're going to figure out how to launch a bean bag as high as possible with a lever launcher!

You'll need:
A board, at least 2 feet long
A rock, scrap wood, or log--almost any sturdy object roughly the size of a shoebox will work (it has to be a lot sturdier than a shoebox though, or you'll crush it flat!)
A sock
Pinto beans, rice or sand

Supervision:  It's important to have an adult or heads-up kid in Junior High or older check your lever before you use it.  They'll spot things like poor balance or nearly-broken materials that would be dangerous.

First, you make a beanbag to launch.  It's easy--just fill a bag with pinto beans, rice or even sand, then tie the top of the sock in a knot so nothing can spill back out.  I recommend drawing a face on it, although this is not strictly necessary.

The rock, scrap wood or log is the fulcrum--the lever (the board) pivots up and down around the fulcrum.  Mr. or Ms. Bean Bag is the load.  You are the applied force--when you jump on the lever and send the Honorable Judge Bean Bag flying! Set up your lever like this:

The fun part is figuring out how to send Archduke Bean Bag flying the highest! Try moving the fulcrum so it's not in the middle anymore.  You can move it closer to or farther away from Princess Bean Bag.  Is it better to jump at the very end of the lever, or closer to the fulcrum?  Have fun finding your favorite way to sent Baroness Bean Bag whizzing through the air!

Mini Monday: Cup Communicator

Hi girls!  This might be the simplest Mini Monday yet, and it's a lot of fun!  All you need are two cups or cans--tin ones work really well--and a piece of string.  Poke a hole in the bottom of the cups, pull the string through and tie it in a knot.  Now hold the string taut, so the cups are as far apart as possible, and talk into one while someone else put the other one up to their ear.  Ta-da--communicator!
Sound travels in waves that are really just bunched-up air--but it doesn't have to be air!  Here, the waves are travelling down the string instead.  The cup is an amplifier, so it makes the sound louder.  That's why even when another person is standing nearby, if you whisper into the cup your partner can hear you and the person can't!

Enjoy girls!  There will be no post this Thursday due to Thanksgiving, so check back in next Monday!

SPY WEEK: Periscope

Spies operate in secrecy.  If someone realized what they were up to, they'd be marked--and that's trouble.  So how do you see without being seen?

One way is with a periscope.  With one, you can spy from behind something and no one can see you--but you can see them.

What you need:
Cardboard
2 mirrors (Square or rectangular, but not circular--circles are hard to work with. You can get them at a craft store or by taking apart old makeup compacts--do ask first for that last one.)
Tape or hot glue gun

Supervision:  This project can be tricky; adults can help.  I think it's a good idea to ask an adult for help if you are still in elementary school.

The periscope works by reflecting (bending) light.  It basically works just like the diagram below:

The mirrors in the diagram are actually fit inside a long thin rectangular tube.  It can be as long as you want.  However, it should have the same (or larger) width as your mirrors, so they fit.

If you're older, it might be a good idea to just look at the diagram above and make the periscope from that.  However, I do have tips.

Okay, first you need your rectangular tube: you can just fold cardboard into one.

Next, you need two holes: one so the light can hit the top mirror, and one so it can bounce into your eye from the bottom mirror.  To get the top hole, I recommend tracing your mirror at the top of the tube, and cutting that out.  For the bottom hole, you also trace, but you trace on the opposite side of the tube (see how the light  in the diagram comes in from the left, but out on the right?  That is why the top hole needs to be on one side, and the bottom hole on the other).

Keep the piece of cardboard you cut out!  It can make it easier to glue or tape the mirror in the tube at the right angle.  Cut the piece in half diagonally to make triangles, and lean the mirrors against the triangles when you attach them to the cardboard tube.  See how I did it in these next pictures:

Do the same thing on the bottom of the tube, only this time the reflective side of the mirror faces up (toward the other mirror):

Looking up the bottom of the periscope

It's finished!  You can add handles, decorate, or camouflage your periscope however you like.  To use it, hold the periscope upright and look through the bottom hole at the bottom mirror.  Even if you're behind a fence, if the top of the periscope is above the fence, you can see over it!

Can you see my eye? Creepy!

Ack! We've been spotted!

Periscopes in the real world work by bending light, just like ours!  They're not just used by spies--they were very useful in submarines during World War II.  Nowadays, periscopes can be very fancy.  This is my friend Captain Toll.  He's a Bioengineering student at my school, too, but he's also a tank commander.  See the reflective rectangles above him?  Those are periscopes!  There are eight in his tank, and they let him look all around for danger, without ever leaving the tank.

Hooray for periscopes!  Now, go conduct your covert missions!

SPY WEEK Mini Monday: Invisible Ink

You're walking down the sidewalk when you notice the reflection of someone behind you.  Good, she's here--but you pretend not to notice.  You reach the mailbox and without slowing down, without looking left or right, slyly drop a crumpled paper out of your pocket.  As you turn the corner up ahead, you catch a glimpse of the mailbox: there is a streak of chalk on the mailbox, and the paper is gone.  Message delivered.

Real spies send secret messages a lot like that--in fact, during the Cold War there was a spy who did actually mark mailboxes with chalk when a message was delivered!

But what if your friend didn't get the message?  What if someone intercepted it (that means when someone else gets something instead of the person who's supposed to)?

Well, they'll think they just got a piece of blank paper, because I'm going to show you how to make invisible ink!

What you'll need:
Real grape juice
Baking soda
A spray bottle
Paper
A small paintbrush, the corner of a sponge, or your finger

Supervision: No adults needed!

First, put a little bit of water in a cup--you only need about a teaspoon full.  Then mix in a pinch of baking soda.  Keep mixing in baking soda, a pinch at a time, until some settles on the bottom of the glass--that means the water is full, or saturated, and no more baking soda can dissolve in it.

Now, get a piece of paper and write on it with the paintbrush, sponge or your finger dipped in the baking-soda water.

Let it dry completely (about 20 minutes) before you deliver your message.  If there's any dust on it after it dries, just brush it off or crumple up the paper.

To read the message, you need a light mist of grape juice on the paper.  Grape juice is an indicator (just like litmus paper) that turns green when it touches a base like baking soda.  The writing turns green, and the rest just stays purple.  Put the grape juice in the spray bottle and spray just a little bit near, but not directly on, the secret message.  If it gets really wet it won't work: you just want a little bit of grape-juice mist on the message.  Anyone who doesn't know to use grape juice on the letter will never be able to read it!  Only tell friends you trust.

Here are some tips for being particularly sneaky.  Real spies use false clues so the wrong people don't read their messages.
1.  Write the secret message using code words
2.  After the message is dry, write a fake message over it in pencil that anybody could read.  Make it either really boring, or fake secrets.
3.  Write the secret message on something you could carry without looking suspicious, like an old homework assignment or a school handout.  Put a small mark in the corner (like a star) so that someone in on the secret knows what it really is.

All right girls, have fun with your clandestine operations!

Volcano!

Welcome, welcome, welcome to what is possibly the most classic fun science project ever!  Yes, today we are doing the ever-popular, much-loved baking soda and vinegar volcano!  Acetic acid in vinegar reacts with sodium bicarbonate in baking soda, so it really erupts!  It's completely safe too, from beginning to end.

And you can build the whole thing from scratch!

What you will need:
Newspaper.  One or two whole newspapers should be perfectly splendid.
Flour, 1 cup or so
Cardboard
1 or 2 liter plastic bottle
Baking soda
Vinegar
Food coloring (if you want)

Supervision:  Nah, you don't really need adults for this project.  They can still help though!  Grown-ups like to have fun too.

First, you want to create the frame, or basic shape, of your volcano.  Tape the bottle to the middle of a sheet of cardboard (or in the middle of a wide, tall pan baking pan if you plan to set the volcano off indoors).  Tear or cut about 8 strips of cardboard, and tape one end to the soda bottle and one end to the base, just like in the picture below.  Just be careful not to cover up the top of the bottle--you need to pour baking soda and vinegar into it later!

Once you have your frame, you are ready to paper mache!  This is a bit messy, so doing it outside or on a couple layers of newspaper is a good idea.  Mix equal amounts of flour and water together--you can start off with 1 cup water and 1 cup flour.  Scoosh it up with your hands until it's well mixed. Tear your newspaper into long strips about 2 or 3 inches wide.  Dip a strip in the flour goop and slide the extra off with your fingers, making sure the whole strip got some goop on it. 

Next, lay the strip across (not up-and-down) the cardboard strips.  Keep doing this until there aren't any empty spaces or cardboard strips showing.  You can put newspaper strips on top of each other, but not more than four in a stack or it won't dry quickly enough.  Now it might look something like this!  Everybody's is different.

Let your volcano dry for at least an hour or two--you'll be able to feel when it's dry and hard.  It almost feels crunchy.  Next, you can decorate it however you want!  I used frosting, candy and sprinkles for mine, but paint works really well too, especially if you want to take it places or keep if for a couple days (chocolate frosting got all over my co-creator's sweatshirt while carrying it outside).  You can use little plastic toys too if you like--anything that strikes your fancy!

These gummi bears thought it would be a lovely day to go sledding on the mountain by the train tracks.  Oh, fateful decision!  

Once you've decorated, you're ready for the eruption!  Pour baking soda into the bottle inside your volcano.  Use a funnel--or if you don't have one, a rolled-up piece of paper (that's what I used).  The more baking soda, the better--I used one whole box, an entire pound!  If you want, you can also mix in some water, or detergent for an extra bubbly eruption.

Take your volcano somewhere outside where it's okay if things get messy.  If you can't go outside, that's okay, just put it in a deep pan to catch the vinegar-lava.  Speaking of vinegar--it's fun to put food coloring into the vinegar so the lava will be colorful.  I used classic red, but there's no reason you can't have blue lava if you want to!

Is your volcano in position?  Okay...get ready!  Pour as much vinegar in as you can, then step back and watch the destruction!  Wooo yeah!

Mini Monday: Squishy Egg

Hello ladies!  I first tried this project in 8th grade, but if you're old enough to read, you're old enough to do it too!  You will want to get permission from a parent, though.

Did you know the hard, white part of the shell isn't the only thing holding the egg together?  There's also a stretchy, clear thing around the egg called a membrane, but it's under the hard shell so you don't see it--normally!  I'm going to show you how to dissolve away the hard shell, leaving a squishy, clear egg to play with!  

All you need is an egg, vinegar and a glass.  I don't want to give too much away, but you might want to buy the bigger container of vinegar--you might want it for the project this Thursday! Put the egg in the glass, cover it completely with vinegar, stick it in the fridge and forget about it for two full days (it might only take one).  If you want, you can change the vinegar after one day.

When it's ready, the white shell will be completely gone.  It'll be squishy and clear!  You can play with it until it breaks (it's so funny and gross when it suddenly breaks all over your hands!).  It is sure to break because it's very fragile without its white shell--and you probably don't want it to last too long, or it'll get stinky.  I recommend you examine it outside--so it doesn't end up breaking all over your desk in school like mine did (sorry Mr. Wilson!).  (If you are going to take it to school, better keep it in sealed tupperware and show it off outside of class, but you didn't hear it from me.)

So what's going on here?  Well, the hard part of the shell is mostly made out of calcium carbonate, a base.  Vinegar has a lot of acetic acid.  Acids are the opposite of bases, and when they mix together, there's a reaction.  The calcium carbonate gets dissolved away by the acetic acid.  As the calcium carbonate dissolves, the "calcium" part gets mixed in the vinegar and you can't see it.  The carbonate, however, turns into carbon dioxide, which is a gas.  Watch your egg right after you put it in the vinegar--see all the little bubbles on the shell?  Those are the carbon dioxide--you're watching the reaction at work!

New addition to post on Jan 25, 2011: To do more with your squishy egg, check out Mini Monday: Eggy Osmosis!

LED Light Box

Hi girls!

When I was at UC Davis, everyone did Senior Design Projects in groups.  My group made stairs that lit up in bright colors and made a fun sound every time you stepped on them!  We did this so that children at the Easters Seals, who climb stairs for therapy to make them strong and balanced, can have fun on the stairs!

Well, that project took quite a lot of time, engineering and money.  But today I'm going to show you how to do a cheaper, mini version in a day!  This little box lights up when you close the lid.

What you will need:
A small box with a lid
Tin foil
9V battery
Tape
680 Ohm Resistor  (Be carefule not to get 680k--that's a thousand times as big!)
9V battery snap/connectors
LED (Not blue or white--those behave differently from the other colors and won't work with the same resistor.  Any other color should be fine.)
Wires (you might not need wires if your box is small)

(You only need one 680 Ohm resistor--when I went to Fry's, they were out of 680 so I bought a 120 and a 560 Ohm resistor and connected them, so it adds up to 680.)
Fry's and Radio Shack are good places to look for resistors, battery snaps, and LEDs.

Supervision:  You will want an adult handy for this project.  With an adult's help, this project is probably ideal for third grade on up.

This project is based on a circuit.  It is connected together according to the diagram below:

Batteries are power sources.  They give the circuit the voltage and current it needs to light up.

Resistors are like speed bumps to the current.  They make the current lower so it doesn't fry the LED.

LED stands for Light-Emitting Diode.  An LED is a type of diode that lights up when current flows through it.  A diode only allows current to flow one direction, which means that it is possible to put an LED in backwards.  To tell you which side is which, one side of the bulb has a flat part.  Also, that side has a shorter wire coming out of it than the other side. 

Wiring the Circuit

1.  Sometimes it's hard to get two electrical parts to always be touching.  Taping them both to a square of tin foil can help because tin foil conducts electricity, so for the circuit it's the same thing as touching.  (Even better is using tiny wire nuts, which you can get at home improvement stores.)  So the first thing to do is cut out four squares and one long rectangle of tin foil and tape them to your box, just like in the picture below. 

Nodes 1 and 2 fold over the top of your box.  Nodes 3 and 4 are on the bottom of the box, only a centimeter or two apart.  Node 5 should be long, so that when you close your box, it touches Node 1 and 2.  This will connect them so that current can flow and the LED can light up.  Together, Nodes 1, 2 and 5 are the Switch.  Because of them, closing the box will turn on the light.

2. Connect parts to the nodes by placing them on top of the shiny foil and taping them down.

Node 1 connects to one end of the resistor.

Node 2 connects to the black wire on the battery snap.  This leads to the negative side of the battery.  Don't hook the battery up yet!

Node 3 connects to the short-wire, flat-bulb side of the LED.  It also connects to the other end of the resistor.

Node 4 connects to the other side of the LED and the red wire of the battery connector. 

Node 5 doesn't connect to anything (yet! It's part of the switch, remember?).

If your box is big, parts like the resistor might not be long enough to stretch between nodes.  That's okay, just attach wire to that part and connect the other end of the wire to the node instead.

3. If the lid to your box isn't clear, cut a hole in it so you can see your circuit when the lid is closed.

4.  Have an adult check you connections.  Especially make sure the black and red wires on the battery connector don't touch each other.  Then snap the battery on and close your lid.  It should light right up! 

Troubleshooting:
Usually, circuits don't work the first time.  Figuring out what's wrong is called troubleshooting.  Troubleshooting is part of building circuits.  Here are some top things to check if your circuit doesn't work right away:

• Make sure all the connections are actually touching.  Try pushing down on each of them to see if that makes a difference.
• Make sure Node 5 really does connect nodes 1 and 2 together when the lid is closed.  Check that it's long enough, lined up, and that it touches both nodes when the lid is closed.
• Make sure the LED isn't in backwards.
• Make sure the battery isn't dead.
• Make sure the red and black battery snap wires weren't mixed up.

If more than one thing is wrong, troubleshooting can be especially tricky.  Don't worry!  That's how circuit design works.  In college, sometimes people just take the whole thing apart and try again if it's not working after troubleshooting.

If you want, you can build lots of light boxes with different colors!  Have fun building and showing off your light boxes and circuit know-how!

Mini Monday: Corn Starch Stop-and-Goop

Hello ladies, and welcome to the inaugural (that means first) Mini Monday!  Mini Monday projects are small enough to do anytime, even on a school night!

This Mini Monday project is Stop-and-Goop!  It’s a gooey goop when you play with it slowly, but when you hit it quickly, it’s hard!

You will need:
Corn starch
Water

Supervision level: Younger than about fourth grade might want a parent or older kid to help

Mix corn starch and water together slowly, mushing with your hands or swirling the bowl slowly.  You need about 3-4 times more corn starch than water.  I usually start with the amount of corn starch I want—a small handful is perfect—and then add water bit by bit, squishing very slowly with my hands as I go, until it’s good and goopy.  If you want, you can swirl in some food coloring—I put red and blue in mine to make it purple!

Then it’s ready for play!  Some things I like to do with my stop-and-goop are rolling it in a ball really fast and then holding the ball.  What happens when you poke it slowly?  How about really fast?  What if you put your finger in slowly, then pull it out as fast as you can?  Try bouncing it on a table—but be sure to keep it away from carpet, tablecloths and fabric!  (But don’t worry about hard surfaces or your hands—stop-and-goop washes away with plenty of water.)

If you’re curious about how this happens, I have a guess!  There’s a type of material called a “dilatant fluid.”  A dilatant fluid acts like a liquid when there’s not a lot of pressure on it, like when you press on it slowly.  When there is a lot of pressure, like when you hit it hard really fast, it acts more solid.  This is because of the way the molecules behave together.  When they are pressed on softly and slowly, the water can flow along in spaces between other molecules, and everything slides and flows (or goops!) together.  But when it’s pressed on hard and fast, the molecules all get shoved into each other and get stuck!  This sounds like our stop-and-goop to me! 

Have fun figuring out all the different ways to play with stop-and-goop!