## Thursday, June 30, 2011

Hello girls, and welcome to yet another ancient time-keeping technique!  We've learned how to use a candle to keep track of minutes--now, let's think a little bigger.

A sundial uses where the sun is in the sky to tell time.  At different times of day, the sun is in different places.  And when the sun is different spots, shadows go in different directions.  We're going to use the direction of the shadows to tell time.

To make a sundial, you will need:
3 pieces of cardboard
A pencil or straight stick
A protractor
A pen
Scissors
Tape or glue

We need something for the shadows to fall on.  Let's make the face of the clock first.
Put your protractor one inch from the bottom of the cardboard.  Every 15 degrees, draw a small line (at 0 degrees, 15 degrees, 30 degrees and so on, just like in the picture below).  Label the lines just like in the picture.

Now, we need something to make the shadow.  Stick your pencil straight up in the middle of your clock, like this:

Now, here's a tricky part.  The Earth is round, so unless your town is right on the equator (an imaginary line that goes around the middle of the Earth), your town isn't really directly facing the sun.  It's actually kind of tilted toward the sun.  Seriously, it is!  So to make our sundial super accurate, and to make it work all day and all seasons, we're going to tilt our sundial, too!  You will each tilt your sundial a little bit differently, depending on where you are in the world.  Believe it or not, it will make the pencil point straight through the center of the Earth, and the clock parallel to the ground at the North Pole! A tilted sundial is called a gnomon.  I think that's pretty fancy!

To find out how much you want to tilt your sundial, first you need to know the latitude (distance from the equator) of your town.  You can find it at this web site: http://www.travelmath.com/city/, or in an atlas.  Once you've found your latitude, subtract it from 90 to get the angle you want for your sundial.  For example, my latitude right now is about 37 degrees.  90-37 = 53.  Using your protractors, draw that angle on your cardboard, and cut two wedges from one cardboard that have that angle--for example, one of the corners of my wedges was 53 degrees.  Mark which corner of your wedge has the angle you want, or you might get confused!

Now, tape or glue your wedges to the last piece of cardboard on one side and your clock cardboard on another.  This can get a little tricky, so check the details.  Make sure the pencil is near the bottom, not the top, before you glue, and make sure the two pieces of cardboard form the angle you want, and not the angle of some other corner of the wedge.  It should look similar to the one here:

Now, all you have to do it set it up outside!  Find out what time it is, and set your sundial so that the shadow falls on that time.  (The best time to do this is noon, but any time works.)  As the sun moves, the shadow moves, and it falls on the time!

What time did I take this picture?
 7 o'clock!
Now you can tell what time of day ancient women would have thought it was!

## Monday, June 27, 2011

### Mini Monday: Pencil Helicopter

Hello girls, and welcome to a project inspired by seed pods from maple trees!  Maple seeds have wings.  When you drop half of one, it twirls through the air.  We're going to make a simple helicopter from a pencil, cardboard, and a thumb tack, and send it spinning through the air!

You need:
A pencil with a full eraser
Thin cardboard, like the kind cereal boxes are made of
A thumbtack

You don't need any adults for this project!

First, we make the propeller by cutting a strip of cardboard about an inch wide and as tall as the whole cereal box.  Fold it into a slight V shape, and pin the middle of the V into the top of the pencil's eraser with the tack.

You just made a mini-helicopter, simple as that!  Now, roll the pencil very quickly between your hands and let 'er fly!  It's really cool to spin it off a deck, balcony or stairs--anywhere high--so that it has more time to float and spin!

The pencil helicopter sure looks simple, and you would think the science would be, too.  But aerodynamics (which is the study of moving air) is extremely complex.  It's so complex, the things they teach you about in school--even when you're taking physics in college!--are so simplified (making something seem simpler) that they're not the whole story.  They might not even be true!  So as simple as the pencil helicopter is, it has a lot of very complicated science whirling around it.

But I can tell you some of what's going on.  Air is actually a fluid, just like water.  Have you ever jumped in a pool with your legs stick-straight and your arms to your sides?  Have you ever landed on your stomach and belly-flopped?  You go deepest in the pool when you're stick straight, and you stay right near the surface when you belly flop, because of surface area.  Only a small surface area--just the bottom of your feet--hits the water when you're stick straight, so you slide right through it.  When you belly flop, a whole bunch of you hits the water, and the extra surface area means there's a lot more of you that needs to push down on the water.  The pencil without the propeller slides through the air, and falls quickly.  When we add the propeller, we've added a lot of surface area, so it floats gently through the air.  It has more air resistance slowing it down.  Now that you know one of the helicopter's secrets, maybe you can figure out a way to make it go even more slowly.  Want to make another one and race?

## Thursday, June 23, 2011

### Baby Lemon Sprouts

Hello girls!  I hope you all kept a lemon from Monday, because today we're going to use--the seeds!  We're going to grow tiny baby lemon sprouts--and we'll be able to see them better than if they were growing in the ground.

You will need:
Lemon seeds
Water
A jar or glass
Paper towels

No adults needed for this project.

First, we need to soften up the seeds, so that the tiny sprouts don't need to push too hard to get out.  We do this by soaking the seeds in water for an entire day.

The next day, you can get their new home ready.  Line the inside of the jar with paper towel up against the edge, and fill the middle in with bits of paper towel.  Wet the towel so it sticks to the sides of the jar.  Put about an inch of water in the bottom of the jar (the paper towel will soak this up when its own water starts to dry, so it will always be wet).  Finally, slide the seeds in between the paper towel and the jar, up at the highest-reaching part of the paper towel.

 Day 1

These sprouts like a nice, dark place to grow, just like they normally get growing underground, so put them up on a high shelf in a closet (or anywhere else dark and undisturbed) and shut the door.  Now, it's the waiting game.  Don't despair if they don't grow right away--lemon seeds are shy, and take a week to 12 days to start sprouting.  Keep checking every day or couple of days, and add water to keep it at about an inch.  Soon, you will have baby lemon sprouts!

Here's what mine looked like after 11 days:

The picture at the top of this project is a close-up view of the seed on the top left.

Here are pictures of seeds on the other sides of the glass:

It looks like good lemon-growing conditions are also good mold-growing conditions.  Eeew, gross!

## Monday, June 20, 2011

Girls, this has gone on long enough--it's time for junk food.  Today we'll make our own junk food--specifically, sparkling lemonade.  The 'sparkling' means it is basically the same thing as lemon soda.

You will need:
Lemons or lemon juice
Sugar
Baking soda
Water

First, squeeze the juice from the lemons until you have about 1 cup.  Then add one cup of water.  Stir in sugar and take small tastes until you like the way it tastes.  Now, it is regular lemonade.

Now, for the messy, sciencey part, where we transform it from lemonade to sparkling lemonade.  In past projects, we've done a lot with acid-base reactions, so you already know about the reaction made by baking soda, a base, and citric acid in lemon juice.  You might remember that carbon dioxide bubbles are made in the reaction.  And from soda fizz balloons, you might know that the fizzy part of soda actually is carbon dioxide.  With all of these knowings, you might already have a good guess about how we're going to made our lemonade sparkling.  And you might guess we'll want a pretty big glass, and that this is gonna get messy!

If you wanted to try adding baking soda to the lemonade, I agree completely.  You only need half a teaspoon of baking soda--go ahead and stir it in!  It will fizz and bubble just like the reaction we know it is.  Once it's calmed down, have yourself a taste.  Sparkling lemonade, made with science!

I wouldn't want to spoil anything, but--you may want to keep one of your lemons--even if it's squeezed out--for Thursday.  ; )

## Thursday, June 16, 2011

### Salvation at Sea: Getting fresh water from the ocean

Imagine, girls, that you are lost at sea.  Perhaps you had taken up piracy, and your ship was scuttled (sunk on purpose by you) rather than have it fall into the hands of a sovereign.  (Remember, girls, that's the sort of thing that happens when you take up piracy--if you really must, become a lawyer.  Satisfy many of the same instincts, without the risks.)  Suppose that because of this, you are adrift in a lifeboat for days, perhaps even weeks.  You can survive without food that long--but not water.  Try to drink saltwater from the ocean, and you will succumb (give up) even sooner.  You need fresh water to drink.

Fear not, brave ladies.  For in your childhood you did projects here on FSG.  You know what to do.

You grabbed:
A big bowl, like a mixing bowl
Saran wrap
A small cup
A small weight--like a stone or a small handful of pennies
(If you are doing this project somewhere safer than adrift in the ocean, you'll also need salt)

Of course you don't need adult supervision--you're not going to have it on a raft, are you?

First, we have to make saltwater, since that's all we'll have in the ocean and we want to practice.  Just mix about three teaspoons of salt with two cups of water in the big bowl.  This is what you would get just by scooping some water from the ocean into your bowl--take a tiny taste if you want to see what you're dealing with.  Gross!

Next, place your cup in the middle of the bowl.  Put it right side up, of course, so no salt water gets in.  Now, stretch saran wrap tightly over the big bowl.  You don't want it touching the top or your cup--if it does, get a shorter cup.  You might want to tape the saran wrap down, just to be sure it stays taut (tight).  Now, place the little weight on the saran wrap right over the cup.  This causes a dip in the saran wrap.  Finally, put the bowl in the sun and wait a few hours.  Trust me--you'll have plenty of sun in your rowboat!

 This is what it will look like
 Dip in the saran wrap

What happens?  Well, you get a lot of water droplets on the underside of the saran wrap, like in the picture at the bottom.  They got there because the heat from the sun caused water--but no salt!--to evaporate from your salty solution into gas.  It then hit the saran wrap and condensed back into liquid.  But salt doesn't evaporate--so the drops of condensation are pure water!  They roll down the dip in saran wrap, and drip into the cup.  Nice fresh water for a stranded scientific sailor!  Go ahead--take the saran wrap off and drink it!  Perfect fresh water!

## Monday, June 13, 2011

### Mini Monday: Candle Clock

Hello girls!  Today we are going to make a clock.  Not just a clock, but a clock that our ancestors of yore might have made, too, in days long passed.  It's a clock made from a simple candle!

A candle burns at about the same rate for as long as it is lit--that it, the same amount of wax melts during the first minute it's burning, as during the fifth minute, or the eightieth.  We can use this property of candles to turn them into a clock.

You will need:
A candle that does not taper (meaning it must be the same width from the top all the way to the bottom), and it cannot be in a jar.
Several small screws or mug hangers
A ruler or measuring tape
A ceramic plate
A candle holder
Matches
A stopwatch or clock

As always, any project with fire means adult supervision is absolutely required the whole time.

First, if your candle has a pointed tip, let it burn (or have an adult cut it) until it is flat.  Measure your candle.  Now, light it and set the stopwatch.  After half an hour, carefully blow out the candle.  Once it's cool, measure it again.  How much shorter is it?  This is how much of the candle burns in half an hour.  Measure that amount down from the top of the candle, and gently twist one of your screws into the side of the candle on that spot.  Now measure down again, this time from the first screw, and put in your second screw there.  Keep doing this until you run out of screws or candle.  Set the candle on the ceramic plate, and light it (remember that adult--keep her handy!).

Now, every half hour the candle will burn down to a new screw.  When the wax around the screw melts, it will fall onto the plate with a clang--and you'll know half an hour has passed!  Of course, candles aren't the most accurate clock ever, but you'll certainly get the idea--and if you want to be reminded of the time more frequently, you can always adjust the project to ten minutes, or 15, or anything you want--and there you have it!  A clock that doesn't need a battery, electricity, or any fancy electronics--just some screws, a candle and your wits!

## Thursday, June 9, 2011

Hello girls!  Today's experiment is super easy, and it seems obvious too.  But if we've learned anything from science, it's that things are not always what they seem.

You don't need any adults or supervision for this project.  All you need is two ice cube trays and a freezer.  That's it!  If you want to be very science-y about it, you should have a notebook and pen for recording your findings.  (If you don't have ice cube trays, you can just use two containers that are the same shape and size.)

If you want to be very meticulous (very careful about details), you can put a piece of tape on the side of each tray, and label one "Hot" and the other "Cold."  Fill the first tray with hot water, as hot as the faucet can get it without hurting you.  Fill the second one with cold water.  Now, before the hot one gets cool or the cold one gets warm, stick them in the freezer at the same time and shut the door.  Every half hour, take a very quick peek (we don't want the freezer to warm up!) and write down what you notice happening in each tray.

What do you expect to happen? What did happen?  Well, I won't tell you what happens, but I will tell you this: the experiment was first done by a 13-year-old in 1963, and the adults didn't believe him.  But he didn't give up.  Now we know he was right, and even today scientists can't tell for sure why it happens!  If you want to read more about his story, it's here (but it's more fun if you don't read it until after you've done your experiment!).

## Monday, June 6, 2011

### Mini Monday: Stop the Pop!

Hello girls, we're back up and running!  We know all kinds of devilishly fun ways to pop balloons--but this time, we're going to try something different.  We're going to poke a balloon with a pin, and hold one over a flame--without popping them!  We're going to use the power of science to stop the pop!

To work this bit of science fun, we'll need:
Balloons, of course! (Four is best, but you can get away with two)
Tape (most kinds will work--I'm using clear Scotch tape)
A very sharp needle or pin
A candle
Water

Because of the flame, you will definitely want an adult to help you or be there with you.  If you don't have an adult around, you can still do the pin part of the project, just don't try anything with fire.

First: pin-pokin' stop-pop!  Blow up two balloons.  Put a small piece of scotch tape on one balloon and smooth it flat.  You don't need to put any tape on the other balloon--it's your control.  (The control is a group in an experiment that you don't really do anything to, so that you can compare what happens to what happens in the group you do experiment on).  Okay, take your pin and poke it into the control balloon.  What happened?  BLAM happened!  Now, take the balloon with the tape, and stick the needle through the tape into the balloon.  What happened?  You stopped the pop!  A tiny stream of air is coming out of the tiny hole in the tape, but other than that the balloon is fine!  A balloon is made of lots of polymers all holding onto each other.  When you prick it with a needle, you break the polymers apart and the balloon rips with a bang--but when there's a piece of tape there, the polymers don't need to hold the balloon together completely--the tape will do it for them!  That's why the balloon doesn't pop.

Now, balloon in flames.  (Remember, have an adult with you for this part.)  Blow up one balloon normally and tie it off (this is another control).  Now, pour water into the other one.  You don't need to fill it up like a water balloon, just put in what fits in the un-blown-up floppy balloon.  Now blow the rest of the balloon up with air and tie it off.  Light a candle and ever-so-carefully dangle the control balloon just over the flame.  Pay attention to how long it just sits before--BOOM!  Now, try dangling the balloon with water in it over the candle.  It lasts way longer--mine didn't pop at all!  Just like the needle, the flame breaks apart polymers to pop the balloon--except it uses heat instead of a sharp tip.  But water doesn't hold polymers together like tape does!

Water has some special properties that make it different and special--after all, humans need water more than anything else but oxygen.  One of those properties is the ability to absorb heat.  Water draws up a lot of heat inside of it without feeling as hot as something else would.  It's weird to think about something taking heat into itself without getting hot, but it's true (science is just crazy!).  So when the candle is near the balloon, the heat goes from the flame to the outside of the balloon--but then the water inside the balloon draws up the heat, taking it away from the edge of the balloon and into itself instead.  The side of the balloon doesn't get as hot, and it takes much longer for it to get hot enough for the polymers to break apart and pop the balloon.

There you have it!  People would probably never think that it's even possible to stick a pin in a balloon, or put a balloon over fire, without popping it--but now you know how to do exactly that!  Enjoy your project--you can even call it magic and give a magic show to your family!  Science doesn't mind being called magic--it's been happening for centuries!  Some people say magic is science that won't give up its secrets.