What Is Special About Dandelions?

You've probably seen dandelions before: yellow flowers which turn into white fluffy spheres. But, despite these interesting flowers, the part of the plant that the dandelion is named after is actually the leaf! The sides of dandelion leaves have a zig-zag shape because they have very deep dents in them. This zig-zag shape reminded early Europeans of lion's teeth, so they called the plant "dent-de-lion," which means "lion's tooth" in Old French! The name "dent-de-lion" then became modernized into "dandelion."

Although dandelions originated in Europe, they were brought to many other regions of the world and now can be found virtually anywhere! This is because dandelions can survive and thrive in many different environments, including some that are harsh enough to kill most plants. In other words, the dandelion is one tough plant!

In fact, the toughness of dandelions makes them very hard to get rid of. If you simply pull off the leaves and flowers, the plant will regenerate (re-grow), much like a starfish can regenerate if it loses its limbs.

As for the flowers, they are actually composed of many tiny flowers arranged in a circular bunch, which is typically 1 to 2 inches wide. This is called a composite flower. In fact, each composite flower of a dandelion is made up of hundreds of tiny individual flowers! This explains why each composite flower can produce hundred of seeds (one per flower).

Another example of a composite flower is the sunflower. The difference (other than size) between sunflowers and dandelions is that the small flowers in the middle of a sunflower look like little buds. They are greenish-brown instead of yellow and do not look like they have petals. These central flowers are called disk flowers.

The outer flowers (the ones that are bright yellow) are called ray flowers. Dandelions are unique in that they are completely made up of ray flowers. In other words, they don't have any disk flowers. This is why all of the flowers in a dandelion look the same.

Another unique characteristic of dandelions is that they don't rely on insects to carry pollen from one flower to another. This process is called fertilization, or cross-pollination. In contrast to most plants, dandelions can fertilize themselves. This makes it even easier for them to reproduce, making them even better weeds!

Furthermore, the seeds have a unique way of spreading themselves around. You have probably noticed that dandelions become white and fluffy after they have bloomed. In fact, this transformation from the yellow composite flower to the white "snowball" form can occur overnight!

Later on, some of the "fluff" blows away in the wind. These fluffy pieces are actually dandelion seeds being carried by tiny white "parachutes" which float well in the wind. This helps the plant to spread its seeds over a large area, which makes it more likely that some will land in a nice patch of soil and be able to grow into new dandelion plants.

Little Lion Experiment:

To see just how effective these "parachutes" are, find a dandelion in its white fluffy form, and pull off the fluff. Pull slowly so that the seeds stay attached to the fluff! Then collect some similar-sized seeds (basil seeds work well for this). Now that you have two sets of seeds that are similar in size, shape, and weight, you can be relatively certain that any differences in how far the seeds travel will be due to the dandelion's parachute (rather than its size, shape, or weight).

Go outside on a windy day and toss the basil seeds up into the air. Watch them fall and notice how far (horizontally) they travel form where you are standing. Do the same with the dandelion seeds. Notice how much further they travel.

Now, can you see why dandelions sprout up in odd places such as cracks in the sidewalk? You don't see basil plants growing there! Seeds that travel far and wide are able to end up in environments much different than those in which they started. So, if you had a basil plant and a dandelion in a garden, where would you expect to find the next generation of basil plants? Where would you expect to find the next generation of dandelions?

What is Fool's Gold?

You've probably heard of "fool's gold" before, but what exactly is it and how does it differ from real gold? The technical name for fool's gold is pyrite. Like real gold, it is brass-colored, hard, and shiny. However, it is not made out of gold, which is why it's not nearly as valuable.

Pieces of pyrite have jagged edges and can sometimes form cubes. Sometimes pyrite also has a grain (sets of lines, just like in wood). Pyrite can be found right here in Pennsylvania, but it is also located in other states, as well as in Mexico and Europe.

True gold is an element. Elements are the smallest building blocks of everything in the universe. They are made of positively-charged particles (protons), negatively-charged particles (electrons), and neutral (non-charged) particles called neutrons. The only difference between different elements is how many of each type of particle they contain.

Besides gold, some other elements that you may have heard of are: silver, iron, mercury, and oxygen. As you can see from that list, elements can be solids, liquids, or gases.

The smallest piece or unit of an element is called an atom. Atoms can combine with each other to form molecules. Some molecules (like oxygen) are just made up of one element. The oxygen that we breathe is written as O2, since there are 2 atoms of oxygen in each molecule, and the symbol for oxygen is O. In other words, oxygen atoms are floating around in the air in pairs.

In contrast to O2, most molecules are made up of two or more different elements. For example, you may have heard water referred to as "H2O." This means that each molecule of water contains 2 hydrogen (H) atoms and 1 oxygen (O) atom.

You might be wondering why we don't write water as H2O1. It is just a scientific custom to not write 1 when there is only 1 atom of a given element in the molecule. By the same token, you can think of your hand as Finger5Palm since each hand is made up of 5 fingers and one palm.

Make sense? Now let's apply what we just learned and figure out the symbol for fool's gold! In contrast to real gold, pyrite is made of the two elements iron and sulfur. The symbol for iron is "Fe" and the symbol for sulfur is "S." Each molecule of pyrite is made up of 1 atom of iron (Fe) and 2 atoms of sulfur (S). So, pyrite is written as FeS2. In case you were wondering, the symbol for real gold is Au.

Little Lion Experiment:

When pyrite mixes with acid rain, it dissociates (comes apart) so now the iron and sulfur are separated from each other and are no longer grouped into molecules of pyrite. When molecules dissociate, you can't see them anymore since they are broken up into such tiny pieces. So, the solutions (mixture) is clear.

When this solution mixes with groundwater (which isn't acidic), the iron can't remain in the solution and so it sinks to the bottom. But since it is exposed to water and air, it rusts. So, you are left with a rust-colored gel from the wet rusted iron. You may have seen this on rocks at the bottom of streams.

Most people don't have pyrite at home, so we're going to use antacids, which will behave the same way as pyrite does in this experiment. Ask your parents for an antacid tablet (like TUMS or Maalox). This experiment will be easier to see if the tablet is colored instead of white. If you don't have antacids, then ask for a calcium vitamin.

Break off a pea-sized piece, place it between two paper towels, then use a spoon to grind the tablet into a very fine powder. Put the powder into a cup. Add a teaspoon of water (this is like groundwater). Mix, and notice how the dust doesn't dissolve (you can still see it). To mimic acid rain, add a teaspoon of lemon juice (this is an acid). Mix, and see if some of the dust dissolves. The solution should become more transparent (see-through) since there is less powder floating on top.

How Are Rabbits And Hares Different?

This month, you'll probably see a lot of Easter decorations around. So, let's have a look at what makes a rabbit a rabbit, and a hare a hare. Baby rabbits are born with their eyes closed and without a fur coat. Rabbits build nests in which to care for these very fragile newborns. In contrast, newborn hares are fully-developed (with open eyes and coats of fur). Hares do not build nests.

Sometimes common names can make the distinction between rabbits and hares a little fuzzy (or furry as the case may be!). For example, black-tailed hares and white-tailed hares are commonly called jack rabbits, even though they are actually hares (not rabbits). The snowshoe hare is commonly known as the snowshoe rabbit. Cottontailed rabbits, however, are actually rabbits.

So, how did the snowshoe hare get its name? The answer is that, in the winter, it grows very long fur over its feet, which makes them look like snowshoes. Just like snowshoes give people a wider base to walk on, the extra fur on the hare's feet gives them a wider base. This helps the hare run more easily through the snow by not getting bogged down as deeply in it. Rather, it glides over the surface of the snow as it runs.

As its name suggests, the snowshoe hare is completely white (except for the tips of its ears) in the winter, but the white-tailed hare can turn completely white too if it lives in a very cold environment. So, sometimes what seems like a snowshoe hare might actually be a white-tailed hare.

In the warmer months, the hares shed their white coats and replace them with grayish brown coats. This makes sense when you think about the forest when it is not covered in snow. If a hare is running through the forest, it is likely to be seen against tree trunks, dead leaves, and rocks. Since these items are brown and gray, the hare can blend in if it too is brown or gray.

Why does environment make a difference in fur color? The answer is that animals survive better if they can hide from their predators (animals that eat them). One common way to not be noticed is to blend into the background by matching it. In nature, this is called camouflage.

Let's think through why different fur colors correspond to different seasons. In very cold regions, the ground is often covered in snow. So, to blend in with its snowy environment, the snowshoe hare and the white-tailed hare grow white coats of fur. In contrast, warmer environments for the hares have darker backgrounds (like mountains and deserts). So, a brown or gray coat of fur is the best camouflage in these warmer areas.

Little Lion Experiment:

Animals don't decide what color to be; rather they have evolved (adapted over time) to have this camouflage. Basically, the animals that blended into their environments were able to hide from predators, so they survived much more often than those that didn't blend in well. As a result, the hares that survived were those who happened to make coats that matched their environments, while the animals that got caught by predators were usually the ones that "stuck out" and were therefore easier for predators to find. Over time, the only families of hares left were those who blended in with their environments.

You don't generally see many wild animals in the winter, but as the seasons change, you will see many more animals (like birds that had flown south for the winter) returning to this area for the warmer months. You will also see animals that stayed here, but did not leave their shelters very often during the winter. As you look around, try to spot other examples of camouflage in the animals that you see. Think about where those animals usually live (as opposed to where they are when you happen to see them) in order to see how their bodies blend into their environments.

How Do Animals Cope With The Winter?

When you come inside after a walk in the snow, aren't you glad that you have a heater in your house? What would life be like without a heater? This challenge is faced by wild animals every winter.

It is very difficult to survive in the winter for two main reasons: the cold temperatures make it harder to stay warm, and there isn't as much food available (since most plants don't grow in the winter, and many animals migrate to warmer areas). So, animals either need to avoid the cold weather, or find ways to survive in it.

The most common strategy to survive the winter months is called hibernation, in which the animal goes into a deep sleep-like state until the weather becomes warmer. This allows the animal to avoid the cold weather without having to move to a warmer climate (like birds do when they migrate south for the winter).

Hibernation is more than just sleep. It is a way to conserve energy by slowing down all of the body's processes. The animal's body produces less heat so its body temperature gets colder, and the animal also breathes much more slowly. These two bodily changes, along with the fact that the animal isn't moving, allow it to use up much less energy than it does when it is awake.

This is important since animals get their energy from food, and obviously the animal is not eating any food while it is asleep! But if the animal doesn't eat while it hibernates, then how does it get energy? Hibernating animals eat enormous amounts of food right before they hibernate. This extra food energy gets stored as fat (bears can gain 40 pounds per week when they are preparing to hibernate!). Then, once asleep, their bodies use the extra fat for energy. Since the animals' bodies are in "slow mode" during hibernation, they do not require very much energy, and so the fat contains enough energy to sustain the animal through the winter.

Humans cannot hibernate, and so we need to eat every day, but hibernating animals are able to survive weeks or even months just by getting energy from their stored fat. Humans aren't the only animals that don't hibernate though. Grey squirrels, red foxes, and wild turkeys are just a few examples of other non-hibernators.

After you categorize an animal as a hibernator or non-hibernator, it is important to ask what type of hibernation it uses. This is because there are two kinds of hibernation: deep hibernation, and a more mild version called torpor. Deep hibernation is also called true hibernation since it is what we normally think of (sleeping through the whole winter without waking up) when we hear the word "hibernation." Examples of deep hibernators are: box turtles, toads, woodchucks, and garter snakes.

In contrast, when an animal is in torpor, it can wake up occasionally to look for food, then go back to sleep. In fact, some animals perform their normal activities during the day and just use torpor at night. In addition to being able to wake up easily, an animal in torpor has a higher body temperature (about 60F) than it would if it were in deep hibernation (around 41F, which is very close to the temperature of your refrigerator!). Black bears, skunks, and raccoons are examples of animals that use torpor during the winter.

Little Lion Experiment:

Get out a small pot and a thermometer that goes down to 40F (5C) or lower. If you don't have a thermometer like that, then put some cold water in the fridge, which is almost exactly the same temperature (41F) as a deep hibernating animal. Put a cup of warm water on the kitchen table. Let both cups sit for 20 minutes. Make some ice cubes (ask an adult if you need help).

Next, put an ice cube into the pot. Put the pot on the stove over low heat (get an adult to help you with this step). The ice cube will begin to melt into water. Keep checking the temperature of the water with your thermometer (or compare it to the refrigerated water) to see how long it takes for the water to reach 41F. We'll call this the "deep hibernator time." Also note how much longer it takes to heat up to 60F (the body temperature of an animal in torpor). We'll call this the "torpor time." If you don't have a thermometer, then you can just wait until the water is almost as warm as the room temperature water. Also record how much more time it takes to warm up to 98.6F, our body temperature (any household thermometer should be able to detect that temperature). We'll call this the "human time."

The amount of time it takes to reach a given temperature is directly related to the amount of energy (heat) that is needed to warm up the water to that temperature. So, the "deep hibernator time" shows how much energy is needed to go from freezing (which is about how cold it is where the animal is hibernating) to the animal's body temperature. Similarly, the "torpor time" shows how much energy is needed to go from freezing to that animal's body temperature, and the "human time" shows how much energy is needed to go from freezing to our body temperature. More importantly, the difference between the "human time" and one of the other times shows how much energy those animals are saving by only warming their bodies up to 41F or 60F instead of normal body temperature.

How Do Snowflakes Form?

Snowflakes are a beautiful part of winter. You probably know that snow is a frozen version of rain, but why does snow fall in flakes rather than in drops? In other words, how do snowflakes form?

Like rain, snowflakes are formed in clouds (which are made of water vapor and tiny drops of liquid water). Since water freezes at 32 F, the water in clouds can freeze if the temperature is 32 F or below.

You may have noticed that snowflakes can have various shapes. Some look like typical intricate snowflakes (called dendrites), others look like long needles or tubes, while others look like hexagonal (six-sided) plates. If these plates have indentations (notches) in them, then they are called sector plates.

What determines the shape of snowflakes? The major factor is temperature, but snowflake shape is also affected by wind, humidity (how much water vapor is in the air), the amount of dust in the clouds, and the altitude (height) of the clouds.

These conditions are important because they determine how the water molecules (H2O) in a snowflake will be arranged. Whichever arrangement forms the most easily under a given set of conditions is the one that will happen in most of the snowflakes that day. This explains why, on a given day, most snowflakes look similar, but you can always find a few odd ones.

Since some conditions (such as wind currents) change so quickly, each snowflake is usually a tiny bit different than its neighbors. It is possible for two snowflakes to be identical, but this doesn't happen very often. Even if two snowflakes look identical, they are probably a tiny bit different. For example, one snowflake might have a few more water molecules in it than the other snowflake does, but your eyes can't see such a small difference.

As a general rule, there are five different snowflake shapes. Each one is found most commonly within a certain temperature range, as shown below:

Thin hexagonal plates	32-25 F
Needles	25-21 F
Hollow columns	21-14 F
Sector plates	14-10 F
Dendrites	10-3 F

Table adapted from http://chemistry.about.com/library/weekly/aa121001a.htm

Think about the first snowfall of the winter. It usually looks like hexagonal plates or needles. This makes sense since the first snow usually falls when the temperature outside has barely dropped below freezing. The prettiest snowflakes (dendrites) tend to fall in January and February since these months are the coldest.

Little Lion Experiment:

On a day when it is snowing, put a piece of black construction paper in the freezer for 15 minutes or more in order to chill it. Then, go outside and hold the piece of paper so that snowflakes land on it.

The black color of the paper should allow you to easily see the shapes of the white snowflakes. However, the paper may begin to warm up after a while. If the snowflakes are melting on the paper, then you can cool the paper down by simply setting it on the ground against some snow, or standing over it so that it lies in your shadow.

Examine the snowflake shapes and try to figure out which of the five major types you have in front of you (there may be more than one shape on the paper). Repeat this experiment on other days when it is snowing. Try to do it on days with different temperatures (like 10 F, 20 F, and 30 F) so that you can see the different snowflake shapes that form at various temperatures.

Why Is It Often Warmer On Cloudy Days?

Why would clouds make it warmer outside? First we have to know what a cloud is made of. We see them all the time, we know rain comes from them, and we've probably pointed out some that look like animals or other shapes, but we may not know exactly how they are made.

It starts out when water from lakes, rivers, ponds, streams, and other water on the ground evaporates into the air. To say that the water evaporates means that some of the water leaves the ground after being heated by sunlight, and is carried by the air in very tiny droplets or as water vapor (gas) that cannot be seen with the naked eye.

You may have heard that warm air rises. The warm air close to the earth that carries the water vapor is an example of this. As the air rises, it cools, losing the heat that kept the water droplets suspended in the air. This cooling causes the water vapor to condense (turn back into liquid droplets). These droplets land on tiny specks of dust in the air. In other words, the water is no longer carried invisibly by the air, but instead, it clings to the dust particles. Groups of these wet particles make clouds.

How do clouds make it warmer outside if a cloud is only water droplets clinging to dust in the air? Actually, the clouds don't make it warmer outside; clouds keep it warmer outside.

A blanket of clouds covering the sky is a little like a blanket that you use to stay warm in the winter: the blanket holds in heat. Sunlight is the source of energy for the earth, and some of that energy is in the form of heat. On days when there are no clouds, heat from the sun can enter and leave the atmosphere without anything getting in the way. When it is cloudy, the clouds absorb (hold) some of the heat so it can't escape. Clouds also reflect some of the heat back towards the earth.

So, on a cloudy day, some energy from the sun gets into the atmosphere through the clouds, but can't get out again. When this happens, the heat builds up during the day, so it gets warmer outside. On days when there are only a few hours of daylight, the sun doesn't have much time to send some of its heat energy through the clouds, and not very much heat builds up. That's why, even on cloudy days, it's still cold out in the winter.

Sometimes it gets even warmer on cloudy days because of advection. Advection is the movement of heat, cold, and moisture when air moves (when there is wind). When warm air from a tropical climate moves into a cooler area on a cloudy day, the clouds keep in the heat just like they keep in the heat from the sun.

Since warm air can hold water vapor better than cooler air can, clouds that are very high up in the cooler part of the atmosphere do not have as much water, and so they are not as thick. Since thinner clouds let in more light and heat energy from the sun, it is not as warm on a day with high, thin clouds as it is on a day with a low, heavy cloud cover.

To summarize, clouds are made of droplets of water that cling to specks of dust in the air. Some heat energy from the sun can make it into the atmosphere through the clouds, but the clouds trap the heat in by reflecting and absorbing it, causing the air inside the cloud blanket to warm up throughout a cloudy day. Warm air moved by advection can bring heat into an area that will be held in if there are clouds. High, thin clouds do not hold in heat energy well as lower, thick clouds do.

Little Lion Experiment:

In order to see how clouds form on particles in the air, you will need:

• black sheet of paper
• glass jar or mug
• flashlight
• clear bag with ice
• confectioner's sugar

Steps:

1. Tape a black sheet of paper to one side of a glass jar or mug.
2. Have an adult boil about a cup of water then fill the jar or mug part of the way with boiling water.
3. Immediately sprinkle a small amount of confectioner's sugar into the top of the jar.
4. Quickly cover the jar with the bag of ice. Turn out the lights and shine the flashlight into the jar.

You should be able to see a cloud forming inside of the jar as the warm water evaporates, rises, and condenses onto the particles of confectioner's sugar when it reaches the higher air cooled by the ice. You may also see the water condense directly onto the sides of the jar or mug instead of onto the particles, but keep in mind that there is no container for real clouds; only dust particles.

This experiment was adapted from Teacher.net Lesson Exchange; http://www.teachers.net/lessons/posts/14.html

How Do We Hear?

There are so many diverse and interesting sounds in our daily lives that we tend to focus on the sounds themselves, but never really stop and think how we are able to hear them. What exactly is a sound anyway? In a nutshell, sounds are how our brain perceives waves that enter our ears.

Believe it or not, there is nothing inherently noisy about sound waves! The waves are the result of vibrations. For example, when you pluck a guitar string, it vibrates at a certain frequency (frequency is basically how quickly something vibrates). This causes the air around the guitar to get compressed (pushed together) in some areas, while the other areas expand.

Why does this happen? First, keep in mind is that, even though we can't see them, there are billions of molecules (tiny particles) floating around in air. Now, if you carefully watch a guitar string, you can see it go up and down very quickly when you pluck it. So when the string is moving towards you, it bangs into the air molecules and pushes them forward (thus compressing them). When the string moves away from you, it allows the air to expand. This pattern continues as the string vibrates, so you get alternating areas of compressed, expanded, compressed, expanded, etc.

This is like waving your hand in a pool of water. You hand moves at a much slower frequency than a guitar string, but it is a vibration nonetheless. If you've ever done that, then you know how difficult it is to move because your body spends so much energy pushing the water molecules out of the way.

You may have also noticed that waves ripple outwards. This is because the water near your hand gets pushed forward when your hand moves toward it, and it is allowed to expand when your hand moves away from it. The water waves that occur when your hand vibrates in water are similar to sound waves rippling outwards when something vibrates in air.

So, now that we understand what sound waves are, we can see that sound itself is not a result of plucking a string, banging a drum, etc. Only the waves are what result from those vibrations. Sound is just how our brain interprets those waves. It categorizes them according to their frequency, with high frequency (fast waves) sounding high-pitched like a violin, and low frequency (slow waves) sounding low-pitched like a bass.

When sound waves enter our ears, they cause bones in the ear to vibrate. Then those bones cause the fluid that lies in our inner ear to vibrate (like when you wave your hand in water).

Our inner ear also contains many tiny hairs along its surface. Each hair is programmed to respond to a certain frequency of waves in the ear fluid. When specific hairs come in contact with their "favorite" frequency, they send messages to the brain so it will know that that particular frequency has just entered the ear. These signals are interpreted as pitch. How is this amazing sensitivity achieved?

Our hair cells are basically arranged in a line. Each frequency "peaks" (is most intense) at a certain hair cell location, so each hair cell can respond to the one and only one frequency: the one which peaks where that hair cell is!

High frequencies tend to fizzle out quickly, so they only reach the hair cells that are close to the outside world. So, it should be no surprise that these hair cells respond to high frequencies. Low frequencies travel much further and "peak" further inside of your head. So your innermost hair cells are programmed to respond to low frequencies.

So, the lower a sound, the further inwards it peaked in your inner ear. The higher a sound, the further outwards it peaked.

Little Lion Experiment:

Stretch a rubber band around your thumb and index finger. Pluck the rubber band and notice the pitch. Stretch the rubber band by moving your thumb away from your index finger. What happens to the pitch now? Can you guess if the frequency is higher or lower?

After your pluck it, the band will keep vibrating but it won't move as far up or down (the height of the movement is called amplitude, and it corresponds to loudness). The frequency, however, shouldn't change (be careful not to move your fingers though!). If the frequency does change, then the pitch will change since frequency is interpreted by your brain as pitch. So, you can observe the frequency just by listening to see if the pitch changes over time! That allows you to see that the frequency stays the same even though the amplitude decreases.