Electromagnet

Hello girls!  Today's project is pretty easy, and very cool!  We're going to make our own magnets, that switch on and off whenever we want.

You've probably gotten to play with magnets before, like ones on a refrigerator.  Isn't it cool that you can actually make one?

To make a magnet, you will need:
Thin wire, about 20 gauge (people working in a hardware store will know what 20 gauge means and how big it is--you can just ask for it).  You want about 8 feet of wire--the more the merrier.  You can make it work with less, too--I only had 4 feet.  Make sure you get insulated wire (plastic-covered wire).  Wire without insulation would make this project dangerous.
A big, long nail.
One D battery
Electrical tape

Adult supervision is required for this project.

Start wrapping wire around and around the nail, leaving a few inches unwrapped on the end (just like in the picture).  When you have wrapped a few inches of the nail, stop and start wrapping back the other way, over the top of wire you're already wrapped around the nail.  If your wire is short like mine was, you might not be able to do this, but it works better if you can.  Wrap the nail as tightly and neatly as you can.

When you're done wrapping, peel off a little bit of plastic from the two ends of the wire.  Tape one end of the wire to one end of the battery (it doesn't matter which end you choose).  Now, before you touch the other end of the wire to the other end of the battery, we need a safety lesson.  Only hold the wire where it is insulated, so you don't get burned.  For the same reason, don't hold it on the battery for too long.  You can't get shocked in this experiment, but the battery and wires can heat up--that's why you want an adult around.  Don't be afraid to just drop it if it heats up. 

Okay, now you're ready--touch the other end of the wire to the other end of the battery. You just made a magnet!  Drag the nail over some paper clips, and watch it pick them up!

How does this electromagnet work?  Well, electricity and magnetism aren't actually as different as we normally think.  Where there's electricity, a magnetic field is created.  When we wrap the wire around the nail, we add together all the magnetic fields from all the pieces of wire--and the iron in the nail helps too.  That makes it strong enough to actually pick up paperclips!

Mini Monday: Surface Tension Soap Boat

Hello there girls!  Today, we're going to use surface tension to propel forward a little tin-foil boat.

All you need is a sheet of tin foil, a little bit of dishwasher soap, and something full of water--whether it's a tray or a bathtub.  Bigger is better--but it doesn't matter how full it is, just so long as water covers the bottom of it.

You don't need any adults to do this project!

First, fold up your boat from the tin foil.  It can be whatever kind of boat you like, as long as it floats.

Set it in the water--does it zip along?  No, of course not! 

Take the boat out of the water and dab some liquid dish soap on the back end of the boat, where the surface of the water will touch it in when it's in the water.  This is going to be your boat's engine.  Now put the boat in the water again, quickly letting go.  What happens?  The boats slides away, sailing along the water!

What on earth is going on?  Well, surface tension is pulling all along the top of the water.  Imagine a rope attached the the back of the boat, pulling on it, and another rope pulling on the front of the boat--just like tug-o-war with a boat in the middle.  That's what surface tension is like.  Dishwashing soap breaks surface tension where it touches water in the back of the boat, cutting that rope.  With the rope in the back gone, the rope in the front (really the surface tension) can pull the boat away.  Try it for yourself!

If we try it again, it probably won't work--why?  The soap has travelled along and broken all the surface tension--so there are no more ropes to sever, and the boat just sits there.  Drain the water, wash it out, and put new water in to try it again!

Google is having a Science Fair!

Hello girls!  You might be surprised to see another post so soon after our rock candy project—this isn’t a typical project post.  I want to tell you about a Science Fair that Google is having, that you might want to enter!  It’s for ages 13 to 18, and you enter online.  It’s due on April 4^th (at 11:59:59 PM ET), which is in about a week and a half, so you’ll want to decide right away if you want to try it.  Or, you can start a project that will take a long time and be ready for next year.  It’s okay to use something you’ve already started (or finished) for another reason, like your school’s Science Fair, as long as it was during this most recent school year.  Since this is such short notice, that would probably be a great idea.

For this Science Fair, you will create your own project.  You can make it up completely, or find something someone has already done, and do the next step or make it better.  You can work in a team of one or two other people.  Your project will be more rigorous than the things we usually do here—if that sounds like an exciting challenge, I think you should do it!

It’s a global competition, so people around the world can enter!  If you want to enter, go here to check the rules first. That site is also a good place to see all the parts your project needs to have.

Like this site, you can do your project on almost anything. The categories they have are: Computer Science & Math; Earth & Environmental Sciences; Behavioral & Social Sciences; Flora & Fauna; Energy & Space; Inventions & Innovation; Physics; Biology; Chemistry; Food Science; and Electricity & Electronics.

The rules web page also has the different parts of the project you’ll write about.  It basically follows the scientific method, but of course no one teaches it exactly the same way, so if you’re interested be sure to review and see exactly what they want.  I think it’s a really good idea to look at the page they have for teachers, here.  That really gives you an idea of what they want!  The FAQ page is here.  As always, FSG has our page for general Science Fair advice.

This is a sponsored post, which means I get money for posting it—but I would never post it if I didn’t think you would want to know about it.  I knew you girls would be interested in hearing about this, and I thought the video was very fun.

Of course, as always, Fun Science for Girls is dedicated to fun, and I think you should definitely do this if it sounds like fun to you—otherwise, see you for the next Mini Monday!

Grow Rock Candy Crystals

Hello girls!  Have you ever looked at quartz or or geodes, and seen how the light shines off of the flat parts?  These things are crystals.  The molecules in crystals aren't all jumbled together--they are organized, each one exactly where it is supposed to be, like people in a marching band.  This gives them the perfect, flat edges that shine.  But that's not the coolest thing about crystals--the coolest thing is, you can grow them.

Things like quartz and geodes aren't the only crystals around--you can eat crystals too!  Salt and sugar are both crystalline.  Big crystallized sugar is also known as rock candy!  Today, we're going to learn how to grow our very own rock candy!

You'll need:
A tall smooth glass (fewer scratches on the inside of the glass is better)
Sugar
A wooden skewer or chopstick
Food coloring
A clothespin

You will definitely want an adult helper for this project--we will be using very hot water that can be dangerous.

First, we boil about twice as much water as it takes to fill the glass (just to be sure we have enough).  Once it's boiling, pour in some sugar--maybe a quarter cup--and stir until the sugar is dissolved, and you can't see it anymore.  Keep putting in sugar and stirring until no more sugar will dissolve.  As you add more sugar, it might take longer and longer for the sugar to dissolve, but keep at it!

Take the water off the stove and let it cool for at least 10 minutes.  This is important, because if you pour water in a glass when it's too hot, it could be very dangerous.  While it's cooling, dip half of your skewer or chopstick in water and roll it in granulated sugar.  This gives the crystals something to grab onto to start growing.  Set it aside (preferably on wax paper) to dry completely.

Once your sugar solution has cooled, add your food coloring and carefully pour the water into your glass--remember to have your adult helper with you!  Clip the clothespin onto the skewer, and put it in the glass, with the rolled-in-sugar side in the water and the dry, sugarless side up out of the glass.  The clothespin should rest on the rim of the glass, and keep the skewer itself from touching the glass at all.

Now the hard part--we have to wait.  Crystals grow, but they take a long time to do it--ours will probably take a week.  We can't touch or move the glass while the crystals are growing, or it won't work, so put it somewhere it won't get touched, like on a really tall shelf.  (It's probably a good idea to cover the top with some cling-wrap or a paper towel, so no dust gets in our candy.)  Our water is supersaturated with sugar--because it was so hot and we stirred so much, the water is holding way more sugar than it would ever want to normally!  As it cools, and since it's nice and still, the sugar will want to come back out of the water--the opposite of dissolving.  Since sugar can't exactly crawl out of the glass, it comes out by forming crystals on your skewer.  Once it's been forming for a week, take out your beautiful crystal candy, and enjoy yummy, yummy science!

Mini Monday: Whirling Swirling Technicolor Milk

Today, we're going to use science to turn a couple of dots in milk into swirling whirlpools of color!

To do this, you'll need:
A tray
Whole milk
Food coloring
Liquid dish soap

No supervision needed on this project!

Pour the milk into the tray, enough to cover the bottom of the whole tray.  Once it's settled down from all the excitement of being poured, put drops of food coloring all over the surface, like this:

Now, we are ready for some swirling action!  What does dish soap have to do with all of this?  Dish soap breaks the surface tension, letting the food coloring move through the milk instead of being stuck in the dot.  At the same time, the dish soap forms little balls around the fat in the milk.  These balls are called micelles.  The soap and milk have to move around to make the micelles, and that makes a lot of swirls.  That's why we had to use whole milk--there has to be fat for micelles to form around!  There's actually a lot going on in the milk to make these beautiful color swirls, but micelles and surface tension are two of the most important.

Prepare for action, and put a drop of dish soap in three spots in the pan.  Watch the swirling tie-dye pools appear!  There's a lot of fat in the milk--it can keep going for half an hour!

A pendulum shows the world go 'round

Hello girls!  Today we are going to make a pendulum, and use it to see the earth's rotation!
First, some business--Fun Science for Girls will not have any new posts next week because I'm having finals, important tests at the end of every quarter that are a big part of my grade--one of them is half my grade!  It's important to me to do well in school, because the better I do, the more jobs I'll be able to choose from when I graduate--so I have a better chance of getting to pick one I really like.  The bad part of this is I need to spend my time studying next week, not having fun with you girls.  Too bad!

On to fun!  To make this pendulum, you will need:
A thin strong wire, or fishing line
A tennis ball (or similar--you can adapt the experiment if you want!)
A long nail
A piece of paper
Tape
A marker or crayon or chalk

It's a good idea to have adult supervision on this project.  You might like the help, and it's safer for an adult to do one part.

The part the adult should do is the first one: put the nail in the tennis ball.  It's great if the nail goes all the way through!

Tie the wire or string to the head of the nail, and attach the other end of the string to the ceiling.  This is another good place to have an adult--they're allowed to put a hook in the ceiling, and that works best!  You don't need to use a hook, though--you can tape it too.  Attach the string so that the ball is hanging just above the floor, only a few inches up.  Put the paper under the ball and draw a straight line.  Now pull the ball back and get it to swing right over the line, in the same direction.  You've made your pendulum!

It's a good idea to turn off any fans in the room and close the windows if you can.  We don't want wind blowing the pendulum around during our experiment!

The ball should swing back and forth for a really long time without being touched.  After two hours, check the line under the pendulum.  Is the pendulum still swinging over the line?  No!  You might guess the pendulum just moved, that's all, but here's the crazy thing--it wasn't the pendulum that moved.  It was the room!  Isn't that insane?  The pendulum swings along its same-old path, but the earth has rotated in those two hours--and the room rotated with it!

Think I'm just kidding you?  The United Nations building has a pendulum just like yours (well, bigger and fancier, but still the same thing) in New York City.  All the countries can see the world's rotation with that pendulum!

Mini Monday: Soda Fizz Balloons

We know that soda fizzes, and we know it fizzes even more when you shake it up first.  But how much more?  We find out by using soda to blow up balloons!

You'll need:
At least two bottles of soda, the bigger the better
At least two balloons (empty)

You don't need supervision--but be careful to do this somewhere where you won't get in trouble if the soda spills!

Carbon dioxide gas is dissolved in the soda.  While the cap is on, there's no other place for it to go (it's under pressure) but once you open it, it can fizz right out of the water and into the air!  But we're going to put a balloon over the opening, so it has nowhere else to go but into the balloon. 

To make sure your balloon is nice and stretchy, blow it up once and let the air out (I recommend suddenly letting it go, so that it whizzes across the room--for science!).  Take your balloons and soda outside--soda can squirt in this experiment!

Now, unscrew the cap on one of your bottles and put the balloon on it, as fast as you can.  You can't get that first bit of fizz right when the seal is broken, but a bit of gas still might fill the balloon a little.  Put another balloon on the next bottle.  Now, take one of the bottles--and shake it!  Shake it up!  If you want to avoid a mess, you can hold it down on the ground and shake like it's in an earthquake, but it won't fill as much that way.

The balloon fills up with carbon dioxide that escaped from the soda!  Carbon dioxide molecules have a hard time escaping from the water in soda on their own--but when you shake it up, you mix air bubbles into the soda, and carbon dioxide can easily escape by hitching a ride with the air bubbles! Voila!

Before shaking



After shaking the bottle on the right



Shaking both of them!  Which soda has lost more carbon dioxide?
It's the one with the bigger balloon!

Hot Air Balloons

Today, we take to the skies!

We're going to make hot air balloons from regular birthday balloons and paper cups, that rise and fall using heat--just like real hot air balloons.  We'll find out how the balloons change when they get really cold.

You will need:
Lots of dental floss (around 40 feet!)
Two balloons, filled with helium
Two small paper cups
A pencil and safety pin
2 pieces of of tape
A paper towel
A freezer

Supervision: You may want an adult to help you with this one.

First, we need to make a net out of dental floss that drapes over the balloon like a table cloth.  Some strings will hang down past the bottom of the balloon and hold the paper cup.

Cut four pieces of dental floss, four feet long each.  Tie them all together in a big knot in the middle.  (You can find the middle very easily by folding the strings in half.)  You've made what will become the top of your net, with 8 strings hanging down!

Now we make it a net.  First, chose a string.  Put your finger on the big knot and measure 9 inches down from your finger: mark it with a black marker.  Take a new, long piece of dental floss (just over 3 feet long) and tie one end of the new string right on the marker dot. 

Choose the next string from the big knot (any of them will work) and mark that one at 9 inches, too.  Now, take the new string that you just tied to the black mark (the 3-foot one), and measure 4.5 inches from where you tied it--mark the new string there.  Tie that mark to the one you made on the second string you chose from the big knot.  Choose another string from the big knot and repeat this whole paragraph until you run out of strings.  It should look kind of like a big dental-floss spider web:

Now, we must prepare the paper cup to become a balloon basket!  Use the safety pin to poke 8 evenly-spaced holes around the rim of the cup, or ask an adult to help if you're in elementary school.  Widen the holes by poking a pencil into them, until they are large enough to easily thread the floss through.  The cup is ready--now we just have to put it all together!

Drape your net over a balloon.  Tape the big knot to the very top of the balloon so it doesn't slide too much.  The 8 strings hang down the sides of the balloon: tie each one to the cup, using the 8 holes you made. You have your hot air balloon! 

To do our experiment, we need two hot air balloons, so make another one just like the first.

Aren't they fun?  Now we're ready to experiment!

Your hot air balloons probably rise up to the ceiling--for this experiment, we want them to neither rise nor sink, but just hang in midair.  Pull off small pieces of paper towel and stick them into the paper cups until the balloons almost float in midair, not going up or down when you let go.  It doesn't need to be perfect though!

Now--stick one of them in the freezer!  Leave the balloon there 10 minutes, so it's brrrrr cold!  Take it out and hold both balloons' cups in your hands--then let go.  What happened?

The cold-air balloon sinks! 

The balloons are full of gas molecules that are always bouncing all over the place, hitting the insides of the balloon and stretching it out to be really full and big!  They make the balloons lighter than air, so they float.  When we put our balloon in the freezer, the gas got cold and made the gas molecules sluggish and slow, so they didn't hit the balloon as much, and it wasn't as full and big.  The balloon actually shrank a little, even though you might not be able to tell.   Even though the balloon has the same amount of gas as before we put it in the freezer, it isn't as full because the gas shrinks in the cold.  Since there is the same mass of gas in a smaller space, the balloon is denser.  Now, it's heaver than air--and it sinks!

The colder green balloon sinks while the normal red one floats happily

Isn't that crazy?  Can you guess what would happen if you put one of the balloons somewhere really hot--like next to a heater, or blowing it with a blow-dryer?  Try it out and see!