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Girl Scout Scientific Achievement Pin

Explanations Packet

Our advice to troop leaders and supervisors: Inspire curiosity, confidence and enthusiasm in your

Girl Scouts! Be confident even if you do not feel comfortable with your answers/explanations because

the process of learning matters as much as the answer itself. Please feel free to ask us questions!

The Daisy, Brownie, Junior, and Cadette requirements have the same foundations but each packet is a little different. The packets for the older scouts require more in-depth investigations. The answers and hints in this adult/leader guide are full and lengthy explanations, which can be used in their entirety for the older scouts or reduced for the younger scouts in whatever way you feel is appropriate for your group. Please see the scout’s version of the packet to adjust your explanations accordingly. Thank you and please tell us what you think about the program when you have finished with your group!

Longer Explanations for Required Experiments

1. LEVERAGE LEARNING

Vocab Fulcrum—the attachment point of the lever– the spot that does not move when the rest of the lever

moves. It changes the direction of the motion applied by the person using the lever.

Pivot— a word to explain the change in motion because of the position of a fulcrum on the lever. The lever ‘pivots’ around its fulcrum

Effort Arm— the distance from your application of force to the fulcrum of the lever Resistance Arm— the distance from the load or weight you are trying to lift to the fulcrum of the

lever Mechanical Advantage—a factor by which a machine multiplies the force put into it to create a dif-

ferent output force, either greater than the input force or less than the input force. In other words, it is a number that tells you how the machine you

are using is changing the amount of force that you are putting into it. The higher the number, the less effort you have to apply to use the machine. For example, a lever with a Mechanical Advantage of 5 is five times easier to lift.

Effort— the strength and force that you apply to the lever Load— the force of gravity pulling down on the weight that you are trying to move up when you use

the lever

Background Information A lever is a simple machine that makes work easier by changing direction (pivoting) around a fixed point called a fulcrum. Often a lever is made up of a board or rods and might contain wheels. The levers at this exhibit are an example of a class one , which is commonly associated with the seesaw because the fulcrum is in the middle. A class two lever has the fulcrum on the end with the load in the middle (like a wheelbarrow). And a class three lever has the fulcrum on an end with the effort in the middle (like tweezers). The easiest lever will have an effort arm that is longer than the resistance arm or put another way, the fulcrum is closer to the load than the effort. Not all of the levers have mechanical advantage! The second to hardest one requires the same amount of effort as the rope-lifting weight (since the mechanical advantage is one) and the hardest to lift lever is actually harder than the rope-lifting weight (since the mechanical advantage is half, it is actually twice as hard)!

Helpful Hints Help the scout measure the lengths of the effort and resistance arms. Have them read the number on each set of weights to realize that they

are the same and the levers can make the same weight seem easier to lift.

If you do not have a phone or calculator with you, please ask the front desk staff to provide you with one. Make sure that when they are cal-culating mechanical advantage, that they have the measurements cor-rect (don’t read the total at the end of the ruler for the resistance arm– remember to subtract).

1st Class Lever– example: seesaw

2nd Class Lever– example: wheelbarrow

3rd Class Lever– example: tweezers


2. PERIOD PENDULUMS

Vocab Period— the time it takes for a pendulum to complete a full swing (forward and back again) Bob— the weight at the end of the pendulum Amplitude— the angle of the swing in other words, the starting point of the swing in comparison to

the initial resting position of the pendulum bob Equilibrium Position— the initial resting position of the pendulum bob

Background Information A pendulum is simply a rope or rod with a weight on the end of it but the science behind it can be quite complicated. As the scouts will find out from their experiments, the only things affecting the period of the pendulum swing are the length of the pendulum and the force of gravity pulling on the weight of the pendulum’s bob. Why is amplitude not a factor? The higher the amplitude of the pendulum (the greater the angle from the equilibrium position), the more energy the bob has. From it’s higher point, it will swing faster than the bob that starts at a lower energy point. Why is mass of the bob not a factor? All masses fall to earth at the same acceleration because the force of gravity is affecting them differ-ently, compensating for the difference.

Helpful Hints Make sure the scouts have pulled back the pendulums properly– especially in the amplitude ex-

periment since it is based on the angle of the swing Make sure that the scouts are pulling the pendulums back equally far in the other two experi-

ments


3. WHISPER TUBES AND WHISPER DISHES

Vocab Sound waves—Sound is energy that needs to move through matter, think of wind making waves in

the ocean. Sound is caused by vibrations that cause molecules to move in waves. In the air, the molecules move in compression waves. Your vocal cords move air molecules that move in waves until they reach the eardrum of the listener.

Reflection— Like a ball bouncing off of a wall and then changing direction and light beams reflect-

ing off of a mirror, sound waves can be “reflected” at certain angles.

Background Information The Whisper Tube holds in these sound waves and keeps them focused all the way through the complicated system until they reach the end. The Whisper Dishes accomplish the task but a little differently. They are large, spherical reflectors that change the direction of the waves and focus them (like light shining through a magnifying glass and being concentrated into one spot). When you talk into the ring, the sound waves travel from your mouth to the spherical reflector, which acts as a mirror. The sound waves are then reflected to the other Whisper Dish. The sound is focused into the other ring. When sound travels through the air, the waves moves at about 1100 feet every second (that’s just over 750 miles per hour)! Since our Whisper Tube is 130 feet long, this takes close to .12 seconds to travel from your mouth to your ear.

Helpful Hints Make sure that the girls are actually whispering so they get the full effect. Otherwise they’re just

hearing themselves across the room. If they can’t see each other’s lips moving, you might want to come up with a signal to show the

girls at the other end so that they know the message is starting.


4. MINIMAL SURFACES

Vocab Elasticity— the force behind stretchiness. It measures how long it takes for a solid or liquid to stretch

out and then return to it’s original form. Thin Films— a layer of solid or liquid that is just a few nanometers or micrometers thick (much much

smaller than a millimeter). Surface Area— the total amount of area taken up by the surface of a solid (or in this case, liquid) ob-

ject. We’re focusing on the outer edges– like wrapping a present with wrapping paper.

Surface Tension— the tendency of water molecules to stick together, which leads to a resistance to weak outside forces. This means that it forms a very sensitive barrier. Very light objects can rest of the on surface of water (think of the water strider insect).

Cohesion—The tendency of certain molecules to be attracted to each other and “stick together”- for instance, our water molecules in this experiment.

Background Information A bubble is a round pocket of air with a thin elastic film of liquid around it. A bubble in any liquid can exist because the outer layer behaves like an elastic sheet. When soap is added to water it stabilizes the water making bigger bubbles possible. The geometric shape that has the smallest possible surface area is a sphere. Because the water molecules “pull” on each other, they assume the smallest possible surface area...a sphere. When soap is added to the water, the detergent molecules tend to line up with one end pointing in-ward (toward middle of bubble) and one end pointing out. Adding soap to water actually decreases the surface tension of the water but stabilizes the water allowing bigger bubbles. It does not “strengthen” the water. Water molecules electrically attract their neighbors. The stickiness of water is due to two hydrogen atoms being attracted to the neighbors’ oxygen atoms. A “tug of war” takes place between the atoms of water, and they “stick together”. Bubbles can be formed because of this tug of war and the atoms “hanging on” to each other. The metal geometric shapes can cause beautiful 3-dimensional bubbles to form because the soap in the water attaches itself to the edges of the frame for each shape. As it grabs onto multiple points of the frame, the film has to stretch between the walls. As the film pulls apart, minimal surfaces are formed because the film wants to occupy the least amount of space possible. Studying soap bubbles can help solve complex mathematical problems, help us understand the be-havior of liquid substances, and they can help industry eliminate weakening of plastics.

Helpful Hints Think of elasticity as stretchy If they’re having trouble figuring out “soap,” remind them of taking a bubbly bath


5. THE TRUSS BRIDGE (not part of the Daisy program)

Vocab Chords—the horizontal and vertical rods Gusset Plates— the red pieces that the rods snap into Compression— the pushing force that causes stress in the top of a bridge structure Tension— the pulling force that causes stress in the bottom of a bridge structure

Background Information

Beam bridges can span a greater distance with a thicker beam. But there is a limit, because too thick a beam will sag into the river. An alternate solution is to build a beam of triangles, a "truss," which is much lighter than a beam of similar thickness. A truss is extremely strong and stable.

A truss bridge is a bridge composed of connected elements (typically straight), arranged in a tri-angular pattern for strength and stability.

Each element may be loaded in tension (pulling force), compression (pushing force), or some-times both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges. The basic types of truss bridges have

simple designs which could be easily analyzed by nineteenth and early twentieth century engi-neers.

A truss bridge is economical to construct owing to its efficient use of materials. In addition to facilitating the accomplishment of long spans with efficient use of materials, the nature of a truss allows for the analysis of the structure using a few assumptions and the application of Newton's laws of motion according to branch of physics known as statics. For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet. This assumption means that members of the truss (chords, verticals and diagonals) will act only in tension or compression.

This shows the members of a typical Pratt truss bridge. Members are the load-bearing components of a structure.

http://www.answers.com/topic/truss-bridge-1

http://www.answers.com/topic/truss-bridge-1

http://en.wikipedia.org/wiki/Physics

Longer Explanations for Elective Experiments

1. LIGHT IT UP

Types of Bulbs Incandescent— a light bulb with a filament wire made of tungsten. Tungsten (which you might recog-

nize as the element “W” from the periodic table), is chosen for an inter-esting property: it glows hot and bright when electricity runs through it.

Halogen— similar to incandescent except we’ve added halogen gas inside the bulb, which makes the tungsten last longer.

Compact Fluorescent— contains a gas that gives off ultraviolet light. The UV light reacts with a pow-der in the bulb that glows (so that the UV light is visible). Be careful, it contains mercury!

Light Emitting Diode (LED)— there are several LEDs are inside this bulb. LEDs are solid and glow when electricity passes through them.

Bonus word: watts—the unit of measurement for power. When it comes to electricity, power meas-ures how fast electricity is being converted into another type of energy.

Bonus word: lumens– how we measure brightness. One lumen is roughly as bright as the flame burning in one candle.

Background Information Here is a summary of the light bulb qualities for comparisons:

Helpful Hints First ask which bulbs they recognize or if they’ve already heard about certain types Even if your scouts are not required to calculate the cost of each bulb per year, it might be helpful

to run through it quickly just for comparison. Use the factors given to start a discussion about which bulb is better in terms of convenience, the

environment, and cost.

Bulb Cost per year Estimated Life Electricity Usage What it means

Incandescent $1 1 year A lot A lot of electricity is wasted,

gives off a lo t of heat, wears

out quickly

Halogen $3 2 years A lot Like the incandescent but more

expensive. Although it lasts

longer.

Compact Fluorescent $0.42 7 years Less Can be dangerous, costs a little

more up front, but uses less

electricity

LED $8 or less 10 + years A lot less A lot more expensive but lasts

a long time and uses a lot less

electricity


2. SCOPE ON A ROPE

Vocab Lens— a glass or plastic disc meant to refract (bend) light and transmit it as well. A lens can con-

verge light beams (concentrate them) or diverge them (spreading them apart).

Nanometer— a unit of measurement, much too small to be seen with the naked eye. It is one bil-lionth of a meter.

Optical— anything relating to the science of studying light (including how it interacts with other ma-terials and tools we use to study it)

Background Information The smallest you can see with your eyes is about one hundred thousand nanometers (about the thickness of a human hair). With optical microscopes like the ones at our exhibit, you can see things that are as small as ten nanometers. Not all microscopes are optical. Some use “feel” or a scan-ning mechanism to detect small things. You can’t see atoms with an optical microscope because atoms are less than one nanometer in size. We have two scopes: one that magnifies 30 times and one that magnifies 200 times! You might find the latter a little harder to operate. Since the magnification is greater, you are more likely to see the fine trembling in what you thought was a steady hand. It takes a little practice also to find out the best distance to hold the scope to get the clearest image. It’s best to hold the scope right up against the object and then pull back as slowly as possible until the image gets clear. Microscopes are made possible through a series of lenses and even prisms. Our scopes are fairly simple (and different because our light source shines directly onto the object instead of underneath) but here is a diagram of the inside of a typical laboratory microscope:

Helpful Hints Explain to the scouts that microscopes contains lenses and take them to the Light and Lenses

room to see how lenses work by themselves. Can they guess which lens magnifies small things? This is a great introduction to chemistry and the idea that everything is made of smaller objects.

Make it clear to the scouts that this is the case for everything in existence. Nothing is what it seems.


3. AIRPLAY

Background Information Consider the two different types of air we start with at this exhibit: the air coming out of the tubes is moving fast, which is in contrast to the slow-moving air that is already in the room. The ping pong ball manages to stay within the very center of the stream of air because the normal resting air in the room has been pushed off to the side. However, just because air is moving fast, doesn’t mean that it has a lot of pressure, in fact, it has lower pressure than air moving more slowly. So the fast-moving air escapes a little out of the sides of the ball in the tube, slows down and so actually creates a high-pressure zone which helps trap the ball. The tube nearest to the blower, fails to support a ball for a very interesting reason. As the air cur-rents move through corners in the piping, they pile together then concentrate in the lower half of the pipe as it nears the tube opening. As a results, very little air escapes through the first hole (which leads out to the first tube). With no curves left in the tube system, the flow eventually becomes more uniform, and most of it leaves through the second two holes. The effect is that a ball falls down into the first hole. But it is not getting “sucked down.”

Helpful Hints For this experiment, it is best to let the scouts play it out for a little while and learn by doing be-

fore asking the deeper questions. Let them really feel the air currents in the tubes– can they tell where the air currents are flowing? Have them try to levitate the ping pong at different distances above the tube– where exactly does

the air current separate?


4. CONDUCTORS & INSULATORS

Vocab Conductor— a material that allows electricity to flow through it easily (like metals– especially cop-

per– and certain liquids– especially strong acids and bases) Insulator— a material that stops the flow of electricity (plastics, rubber, wood, paper, and cloth) Voltage— the push of an electrical current through a circuit, measured in units called volts. Think of

it as the strength of the current Electrical Current— more like a force than an energy, this is the collected flow of charge inside a

circuit. The charge is motivated to seek it’s opposite charge and rushes through the conductors. (Electricity itself is energy that exists in a ‘field’ outside of the wires of a circuit).

Electrical Circuit— the pathway for the electrical current. Must be an open circuit to allow electric-ity to flow through. If there is a gap in the circuit, it is closed and elec-tricity cannot flow.

Background Information Some of the bars are conductors and some are insulators. Since they are metal, the brass and alu-minum bars will light up the bulb while the ones made of plastic and wood will not. You can use your own body to light up the bulb if you moisten your fingers first (there should be baby wipes at the Magnetic Sculpture exhibit nearby or you can use the sinks in the restrooms/water fountains). There is electricity inside of our bodies (our brains send electrical signals back and forth to other parts of our bodies and we are full of liquids that are more than capable to conducting electricity). The circuit is open when no bar is present and adding the bar closes it. For electricity to flow, we must have direct contact between conductors.

Helpful Hints Have the scouts identify the material of each bar before trying it. If they aren’t sure what they

are, you can give them hints (ex. for the aluminum one, you can mention a soda can). Guessing if it will light up the bulb before-hand turns the activity into a fun game. Compare the concepts of electricity to more relatable motion-based elements in real life to make

them easier to understand (for example: a conductor is like a green light for electricity and the insulator is the red light or think of electrical current like cars moving through traffic that need a ‘road’ to travel).


5. CATENARY ARCH OR GIANT ARCH

Background Information These two arches represent the same concept, but since one is larger, it requires a bit more work and you’re battling gravity during the entire build (this is why the larger version is only included in the older scout packets). The arch you built is self-supporting because it has a special shape called a catenary, which is Latin for “chain” (since it resembles and is inspired by the sagging shape formed by a suspended rope or chain). Every block in the arch is held in place by its neighboring blocks. Forces of compression make this structure very strong. The blocks don’t slide off each other even at the top, because they are held together by compression.

Helpful Hints Make sure that you are placing the numbered pieces in their correct spots and that they are fac-

ing the correct way (for the smaller version, the groove should be facing inward for best results and for the larger version, the numbers should be facing inward).

Tell the scouts not to be deceived– can they tell that the blocks are not perfectly squared? Some have very subtle slants so that they can ‘fit into’ each other.

Either version of this exhibit is a wonderful opportunity to develop teamwork. This is very true for the Giant Arch since it is not possible for one person alone to build it.


6. IDENTICAL TRACKS Vocab Potential energy— energy resulting from position, it is stored and unmoving Kinetic energy— energy based on motion Acceleration— increase or decrease of velocity over time (velocity is like speed except it in-

cludes direction)

Background Information When a ball is placed on a track it is given potential energy. When it’s released, it rolls down the track picking up speed (accelerating) as the potential energy transforms into kinetic. When a ball is lifted to a higher position on one of the tracks, there are three changes that affect the movement of the ball: 1. It’s given more potential energy 2. The track becomes a steeper slope 3. The ball will have to travel a further distance to get to the bottom of the track If you examine the curved slope of a track, you will notice that the further back and higher up the ball is held, the steeper the track becomes. If you try releasing the ball at the steeper section, you can observe that a ball will accelerate much more quickly than when is it released on a sec-tion that is less steep. The ball accelerates the whole time it rolls down the track, however, it accelerates faster when the track is steep and accelerates more slowly as the track flat-tens out. The speed that a ball gains from the steeper section of the track continues and increases as it travels on the less steep section of the track. This allows a ball lifted to a higher position to make up for the lower acceleration.

Helpful Hints It might be best to demonstrate this concept as one demo for the group before letting the girls

experiment in order to make it clear. Acceleration is a little difficult to grasp because we are so used to dealing with speed, so it is

easy to confuse the two. Make it clear that the balls are changing speed.


7. ROCKIN’ RADIATION

Vocab Atoms— the basic building block of matter (anything that has mass/volume). They are too small to see but contain even smaller particles (subatomic particles): protons, neutrons, and electrons. Nucleus— at the center of the atom, contains two subatomic particles (protons and neutrons). It always contains at least one proton. Some are unstable can change (decay) resulting in the release of radioactive particles or energy. Alpha particle radiation— an energy released from an unstable nucleus in the form of two protons and two neutrons that are tightly bonded together. Beta particle radiation— an energy released from an unstable nucleus in the form of a negatively charged particle similar to an electron. Gamma radiation— an energy released from an unstable nucleus in the form of energy similar to x-

rays. The atom does not transform into anything else. Geiger Counter- A Geiger Counter is a particle detector and it measures all three types of radiation.

The sensor, or “wand” is called a Geiger-Muller tube. It’s a gas--filled tube that briefly conducts electricity when a particle or photon of radiation briefly makes the gas conductive. The in-strument amplifies this signal and displays it to the user. The Geiger-Muller tube is one form of a class of radiation de-tectors called ion chambers. Ion chambers instrumented to both detect radiation and determine particle energy levels are called proportional counters.

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