Why Do Leaves Change Color in the Fall?

Every fall we are treated to the grand spectacle here in the northeastern US. It is the fall foliage show in which leaves change color from a bright summer green to varying shades of yellow, orange, red, purple, and brown before falling off. The shedding of leaves occurs only in certain types of trees known as deciduous trees.

Many of us wonder why and how this happens. The story lies in the chemistry occurring in the leaves. Leaves are the food factories in trees. Leaves produce sugars in spring and summer when sunlight falls on the leaves as water and carbon dioxide are combined in the presence of a chemical called chlorophyll.

Chlorophyll is a green-colored chemical (also known as a pigment) that reflects the green portion of sunlight while absorbing other colors. This is what gives leaves their normally green color in spring and summer. Leaves contain several other pigments which are yellow, orange, red and brown in color, but the chlorophyll overshadows the rest.

During spring and summer, when days are long and bright, leaves are able to produce a lot of sugars; they send these sugars to the roots and the stem. But as fall sets in, days start getting shorter and the temperature begins to drop. This sends a signal to the tree that it has to prepare to shed its leaves and manage the winter on stored food (known as dormancy).

The tree cuts off the supply of nutrients and water to the leaves by the growth of a layer at the leaf-stalk connection. This event is called abscission. Once abscission sets in, the chlorophyll in the leaf breaks down quickly and loses its color. It is during this period (fall) that we see leaves of trees like birch, beech, cottonwood, hickory, willow, etc., turning yellow. Others, such as maples, sweetgum, and sumac, turn red. Purple is seen in dogwoods, some species of ash and some maples. Several oaks turn brown.

Some factors that control the colors include the temperature, the humidity (wetness), and the amount of sunlight during fall. Bright, sunny, cool days and chilly nights (without frost) create the brightest colors. The leaves exposed to bright sunlight might turn red, while those on a shady side may turn yellow. Wet weather usually leads to decrease in the brightness of the colors.

There are several places in US that have excellent fall foliage displays: New England, New York, Pennsylvania, even some parts of Idaho and Texas. But note that mountainous trees such as conifers (cedars, firs, pines, spruces, etc.,) do not change color and remain green throughout the year. Individual leaves on conifers sometimes stay on for three to four years.

Little Lion Experiment 1:

We will try to do some experiments to separate out the different colored chemicals in leaves (both green and fall leaves). Note that you must have adult supervision during these experiments because use of some items requires extra care and prior knowledge of safety. The process of separation of colors using chemicals is known as chromatography.

Items Needed:

• Rubbing alcohol (ask your parent)
• Hot tap water (ask your parent). Be careful not to hurt yourself.
• A coffee mug
• A large bowl or deep container that can hold the coffee mug
• A pencil
• Scissors (be careful while using)
• Clear plastic wrap
• Coffee filter paper
• Green leaves and some yellow or red leaves

1. You will begin by cutting 2-3 green leaves in small pieces with the scissors.
2. Then you can crush them in the coffee mug and you can use a spoon to further mash them gently. Add some rubbing alcohol to the coffee mug--just enough to cover the leaves in the bottom.
3. Place the mug inside the large soup bowl or container and pour some hot tap water outside the mug so that it can get warm. [NOTE: this is the ONLY safe way to heat; do not try any other method. And keep the set-up away from all kinds of stoves]
4. Let the leaves soak in the warm rubbing alcohol for an hour or more.
5. Put plastic wrap over the mouth of the mug to slow evaporation of the alcohol.
6. If the water in the bowl gets cold, take the mug out, and empty the bowl and fill with new hot water. Replace mug back in position.
7. Wait until the liquid in the cup gets dark, showing that pigments are dissolved in it.
8. Using scissors, cut the filter paper (if you don't have filter paper, use paper towels) into one or two strips about 4 inches long by 1 inch wide.
9. Put the pencil down across the mouth of the cup and drape the filter paper across the pencil so that one bottom end touches the bottom of the cup through the liquid.
10. Let this stand for about 30-40 mins. What happens?

This works best if you seal the coffee cup with plastic wrap so that the alcohol does not evaporate. Sometimes you might have to soak for over 2 hrs depending on the leaves.

The pigments will move at different rates through the paper, and if you wait for 30 or 45 minutes, you will see them separate. The paper strips can be dried and you can keep them as a record. Next you can try this with yellow/red leaves. It is also a good idea to write down the name of the leaf (tree) with each strip if that is possible/known.

Little Lion Experiment 2:

This is a very simple way to preserve bright colored leaves:

1. Gather pretty leaves from trees.
2. Wash them gently to remove dust, and dry them with paper towels.
3. Place each leaf between two wax paper sheets. Keeping a cloth on top, ask an adult to run a warm iron over to press the wax paper to the leaf.
4. You can then cut the paper along the edges of the leaf and preserve it.

References:

• http://www.sciencemadesimple.com/leaves.html#autumn_leaves_science_project
• http://blogs.cjonline.com/index.php?entry=382
• http://portlandme.about.com/cs/fallfoliage/a/leaveschange.htm
• http://www.esf.edu/pubprog/brochure/leaves/leaves.htm

What is the Chemistry of Cooking?

Cakes, cookies and pies--who does not love these yummy baked goods? Have you ever seen these goodies being made or actually participated in making/baking any of these? There is lot of chemistry involved in our cooking.

If you had watched anyone bake a cake, you might have noticed them add a pinch of baking soda or baking powder with the flour. These chemicals help in leavening the flour (leaven: to make light/loose). The principle behind the use of baking soda depends on acid-base reactions that eventually release carbon dioxide gas to help the flour rise.

Acid-base reactions are chemical reactions between an acid and a base. Chemists define acids as substances that can accept electrons and bases as substances that can donate electrons. Acids are commonly found in our day to day life and they can be dilute or concentrated. Citric acid is an acid found in common substances such as lemon juice and orange juice. Acetic acid is found in vinegar. These are dilute acids, whereas concentrated acids are not generally kept around home as they can be quite dangerous.

Bases, on the other hand, behave chemically opposite to acids. Many household cleaners are basic or alkaline. When bases and acids react usually the exchange of electrons also releases heat. Most acids and bases react to form salts (minerals) and water. For example, the reaction between hydrochloric acid and baking sodium hydroxide (a base) would form water and common salt.

The main chemical in baking soda, sodium bicarbonate, contains carbon dioxide in bound chemical form. When it reacts with an acid, it releases carbon dioxide gas and water. This is why most cake recipes call for a small amount of vinegar or orange juice. The acid in these liquids reacts with the baking soda to quickly produce carbon dioxide gas that can bubble through the flour mixture, making it rise in the process.

There are also several other acid-base reactions that can occur even inside the body. The stomach contains acid that helps break down bonds in the food. It also reacts with alkaline matter in the food. If someone has acidity problems, the antidote is to eat/drink something alkaline to neutralize the acidity.

For more information on acid-base reactions in our body, see http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-2/Acid-Base-Reactions.html

Little Lion Experiment 1:

Items needed:

• Vase or wide-mouthed clear jar
• 1/4 cup vinegar or lemon juice
• 3 teaspoon baking soda
• Food coloring

Procedure:

1. Fill the vase/jar with clean water.
2. Add 3-4 drops of food coloring.
3. Add vinegar then add baking soda slowly into the beaker.
4. Drop in rice, buttons, pasta - and watch them rise and fall.

Experiment source: http://www.armhammer.com/myfamily/kids/magic_beans.asp

Little Lion Experiment 2: Writing With Invisible Ink

These are instructions for making non-toxic invisible ink using baking soda (sodium bicarbonate).

Items required:

• Baking soda (not baking powder)
• Paper
• Q-tips
• 2 paintbrushes (at least 1)
• Small cup
• Cranberry juice or purple grape juice.

Procedure:

1. Mix equal parts water and baking soda to make a paste. We recommend starting with a small amount (about 2-3 table spoons) first. Sometimes you can dilute it more.
2. Use the q-tip or paintbrush to write a message onto white paper, using the baking soda solution as 'ink'.
3. Allow the ink to dry.
4. To read the message paint over the paper using another brush with purple grape juice. The message will appear in a different color.

Source: http://chemistry.about.com/cs/howtos/ht/invisibleink2.htm

How Do Fireworks Work?

You probably saw, or at least heard, fireworks earlier this month for July 4th celebrations. The idea that explosions cause loud sounds along with bright lights is commonplace. You've seen it with lightning, sparklers, and a host of other things. But how do firecrackers work? What gives them their beautiful colors and carefully-arranged patterns in the sky?

Fireworks have been around for centuries. They were invented in China, but are now enjoyed all over the world. A firework is basically a timed explosion of a precise chemical mixture in order to produce loud noises and colored lights after the firework has shot up into the sky.

Each firework is composed of two cylinders: a small lifting charge cylinder on the bottom and a large shell on top. The lifting charge is the first source of fuel for the firecracker. When lit, it explodes in order to propel the shell upwards like a rocket.

The shell consists of four main parts. The container (made of paper and strings) wraps around the rest of the shell to keep everything in place. The actual color-producing chemicals (also known as color-emitters) are bundled up into small stars which can be arranged so that the individual bursts of light will form a neat flower-like pattern in the sky. The bursting charge is the fuel for the shell and it is located at the core of the cylinder so that the stars will explode outwards.

The last part of the shell is a fuse which carries the spark from the lifting charge cylinder to the stars in the shell. Since it takes time for the spark to travel, the fuse allows engineers to control the length of time between when the firecracker takes off and when it will explode. Increasing the length of the fuse will delay the explosion for a longer amount of time so that the fireworks will burst even higher in the sky.

Until the production of chlorates (pronounced KLOR-ates) in the 1800s, fireworks only came in yellow and orange varieties since those are the only colors (besides grey) that resulted from burning the firework shells. The addition of chlorates allowed chemists to produce red and green explosions. Safe chemical mixtures that produce blue and purple flames were not developed until the 1900s.

Obtaining pure bright colors is extremely difficult when dealing with fireworks. Many of the color-emitters are so fragile that they would decompose (break down into other chemicals) if stored in the shell of a firework. To solve this problem, chemists devised mixtures of other chemicals that will react to form the desired colored compounds once the firecracker is ignited.

Another dilemma is that, during the explosion, many of the byproducts (unwanted chemicals formed in the reaction) are gray or yellow so these compounds can make the color of the flames look washed-out.

For more information on fireworks, and an interactive demonstration, visit http://science.howstuffworks.com/fireworks4.htm on the web.

Little Lion Experiment:

To see how chemical reactions can produce colors that you might not expect, try this experiment (it's best to have an adult around for the first part). The chemical reactions used in fireworks are very dangerous, so we will be using other chemicals to illustrate the point [do not try to make your own fireworks!].

Grate about half a head of red (purple) cabbage (be careful not to cut your fingers). Place the grated cabbage in a pot with enough water to cover the cabbage, and boil it for 20-30 minutes. The water should be dark blue or purple at this point (if it's not, then boil it for a few minutes more). Then, pour the liquid (careful - it's hot!) through a strainer into a bowl. Throw out the cabbage pieces in the strainer. Let the purple liquid cool.

Pour a few tablespoons of white vinegar or lemon juice into a small cup. In a different cup, mix some detergent or baking soda in water. Then add a few drops of your cabbage juice to each cup. See what happens. Are the solutions the colors you expected?

Why Can't Oil and Water Mix?

Have you ever wondered why oil and water do not mix? Chemistry gives us a clue, saying that liquids which are made of similar molecules tend to mix with each other easily. Molecules are some of the fundamental building blocks of matter.

Oil and water are made of different kinds of molecules which interact differently with each other so they do not tend to mix. The molecules of water, for instance has a more "electronic interaction" whereas oil has "non-electronic interactions."

Further, a drop of oil is usually lighter than an equally sized drop of water, so usually oil floats on top of water when the two are present in the same place. In other words, water is more dense than oil. You might have seen this when you place a drop of butter on top of a hot soup. Soup is mostly water and butter has a lot of oil in it, so as the butter melts it floats as a thin layer on the soup.

This is the same thing that happens when an oil spill occurs if a ship carrying petroleum (crude oil) breaks while on the sea. The oil spills and floats on top of the sea water causing lot of pollution and problems to aquatic life. Of course, oil spills occur very rarely and the more common reason for oil in the ocean water is from cleaning and rinsing of ships.

Just like cleaning oil spills can be a problem for environmental scientists, removing grease from clothes is a problem for all of us. Fortunately, although oil and water do not mix, there are chemicals like detergents which are attracted to both oil and water and can aid in their mixing.

When a detergent is added and mixed up between the oil and the water, it holds hands with oil and water molecules and helps in getting the oil rinsed off with excess water. Such a mixture where oil and water can finally be together with the help of another substance is called emulsion.

Some emulsions which are actually edible happen to be milk, butter, mayonnaise, etc. Of course these are not made with detergents! In summary, oil and water will not mix by themselves because of many different properties, but they can be made to mix with the help of things like detergents or emulsifiers. Since oil floats on water, a lot of fun (but messy) experiments can be done using oil and water.

For fun experiments about oil and water, see http://www.epa.gov/nps/kids/SHAKE.HTM.

Little Lion Experiment:

We will learn how oil and water interact . Caution: These experiments can all get pretty messy, so do NOT attempt them on carpeted floors at all. Also, it is advised to not do it on a wooden floor either, as any spill can be slippery and dangerous. These are best done on a garage floors, preferably with a lot of paper towels around and a small box of sand nearby.

You will need:

• Water
• Vegetable oil
• Glass jar or clear drinking glass (an old pasta sauce bottle will do the job)
• Food coloring (optional)
• Salt
• Detergent powder or dishwashing liquid.
• A wide glass bowl.

Steps: Experiment 1:

1. Pour water halfway into the glass jar.
2. Pour quarter cup oil on top of the water.
3. Let the liquids settle and observe what happened, which layer is on top, etc.
4. If you have food coloring add a drop or two to the top surface and wait and see what happens.
5. Another thing you can do is, sprinkle some salt to the top of the oil and see what happens.
6. You can also now try pouring a small amount of water using a table spoon to the top of the oil layer and see what happens to this new water.
7. Add some detergent powder or a few drops of dishwash liquid and mix things up with a spoon. Allow mixture to settle and see what it looks like now. Do you still see two clear layers?

Steps: Experiment 2:

1. Pour water halfway into the glass bowl.
2. Take a table spoon of oil and try to form a small region of oil film on the water.
3. Try to see if you can break the oil film into several small regions with your spoon.
4. Then try putting them back together into one film.
5. Sprinkle some detergent on top of the oil and mix it up.
6. Now see what has happened to the shiny oil film.

What is Wind Energy?

Wind energy! This is one energy form which humans have been using for several centuries. It is a type of mechanical energy, which means it is energy derived from motion. Do you know how the wind is caused? Ultimately, it is due to the Sun. The energy of the Sun heats up different parts of the air in the earth's atmosphere unevenly.

The farther you are from the equator, the lesser is the amount of the Sun's energy reaching the surface. This difference of heating causes the air in some places to get heated more, whereas the air in some other parts is still "colder." Since warm air is lighter than cold air, the warmer air rises up leaving a void which is taken up by cold air moving in from nearby places.

This movement of air is the wind. Since the earth is also rotating at the same time, the air also moves across the surface of the earth causing wind. The same principle can happen locally too, especially near the sea.

Sand gets heated much more faster than water, and so during the day the air above the sand (on land) gets hotter faster and tends to rise up. The air above the water is still cooler and moves in towards the land, causing a breeze during daytime.

At night, the reverse occurs as the sand cools off faster but the water still has some warmth gained during the day. So the air above the water is warm and now rises up, and the air from the land flows towards the sea.

The power of the wind has been used for moving boats, grinding grains or drawing water for several hundred years. It is now used to generate electricity too. The windmills are like reverse fans. Wind mills typically have 2-3 blades (called turbine blades) and one generator.

The moving blades rotate a magnet which is housed inside set of copper wires. When a magnet rotates inside the copper wire, it causes electricity to flow in the copper due to magnetism. Thus electricity is generated. In Pennsylvania, Somerset county & Williamsport are good places for wind power. When a lot of windmills are together at one place they are called wind farms!

For information on wind energy see the website by the US Department of Energy: http://www.eia.doe.gov/kids/energyfacts/sources/renewable/wind.html and the website by Alliant at http://www.powerhousekids.com Look under Fun & Games (purple menu bar on webpage) for "Cool Projects to Try at Home."

Little Lion Experiment:

We will learn how to make a small wind runner or wind fan. You will need some paper (from any notebook or copier) or long slender leaves (optional), a thumbtack, a pencil with eraser at one end, and scissors.

You can make wind runners using long slender leaves or paper. For making a wind runner using a leaf, please see the diagram which illustrates how to cut off one half of the leaf on either side of the center line leaving some space in the middle to make a hole. It is best to pick slender leaves that are green, a bit sturdy and have a smooth edge all along.

You can then pierce a small hole with a thumbtack through the hole and push it into the eraser of a pencil on the other end. Once the leaf is secure between the tack and the pencil, run around and see the leaf rotate like a fan. You can also try fixing this to your bicycle handle bar and watch it spin fast!

How Do Plants And Water Break Rocks?

You have probably seen people use big hammers to break rocks (in movies) or bulldozers to knock down large buildings. Did you know that plants too can break rocks? Have you seen tiny plants come out of cracks in the road or a concrete sidewalk? It is amazing to see a tiny plant break apart a big rock as it grows in a crack in the rock.

Plants exert a large amount of force on everything around them. All this hidden strength in plants and seeds come from the process of imbibition. Imbibition simply means taking up or absorbing water. This process can be understood by knowing what plants are made of.

Plants are made up of millions of little cells. Cells are the building blocks of living organisms. In plants, the cells are close together but are still set apart by a large number of pores, empty spaces between cells in plants.

Each cell in a plant has a flexible outer covering called cell wall. When the plants or seeds are near water, they absorb the water into their pores and also into the cells. Since the cell wall is flexible, it allows the cell to expand in size and yet not break.

The expansion of all cells is what causes a seed to enlarge so much or wood to swell. Did you know that long, long ago (several thousand years ago) the people who built pyramids in Egypt and temples in India used the power of the swelling in wood to break large rocks?

They used to place wooden wedges in cracks of large rocks, pour some water, and wait. In a few days the wood would swell up and slowly crack the rock open. Then the broken rocks were used to build pyramids and stones. The ancients even used the swelling to wood to lift the rocks, but that story is difficult to explain here!

Other fun experiments on plants are at: http://mgonline.com/experimentsforkids.html. It is going to be spring time so growing plants is the fun thing to do! For information on pyramids and temples visit: http://www.historyforkids.org/learn/egypt/architecture/egyptarchit.htm and http://www.templenet.com/tamilnadu.html.

Little Lion Experiment:

The great strength of wood-based materials when they expand due to water absorption can be easily shown at home. Seeds and beans (whole dry beans) are similar to woody matter and swell if soaked in water over a few hours. The interesting thing with soaking beans or seeds in water is that you will end up getting sprouted beans after a couple of days.

This experiment can be set up in few minutes, but will show results only after few hours, so some patience will be needed. You will need these materials:

• dry beans (green mung beans, or red kidney beans or garbanzo beans - you have to use dry beans)
• a small plastic container with a lid (yogurt containers with clear lids work best)
• water
• a large plastic bowl or plate

Steps:

1. Fill the container with dry beans leaving small amount of room at the top.
2. Set this container into the large bowl or plate.
3. Add water slowly to the beans until you see water reach the top.
4. Place the lid on the small container and close it firmly. If you use plastic wrap, you can clasp it tightly to cover the top and then put a rubber band around the container wall.
5. Write down the time, and check the container at intervals of 1 hour.

Why Is Natural Gas A Cleaner Energy Source?

Coal, oil, and natural gas are all important fossil fuels for heating our homes, generating electricity, and fueling vehicles. These energy sources are called fossil fuels because they are formed from the fossilized remains of plants and animals that lived thousands of years ago.

However, even though all three fossil fuels are formed from decaying organisms (living things), both coal and oil produce a variety of harmful byproducts when burned, while natural gas only produces carbon dioxide and water vapor when burned. This is due to differences in their final chemical compositions, which are due to the different processes (trapping, compaction, and heating) naturally taking place underground.

In general, natural gas has the simplest chemistry and is only made of one carbon atom and four hydrogen atoms (atoms are the fundamental building blocks of all matter), while coal and oil are much more complex.

The simple chemistry of natural gas allows it to have almost 100% energy conversion when it is being burned. This means that the majority of the fuel is being utilized for power needs and only a small amount of the fuel is not being used for power needs.

On the other hand, the harmful byproducts that coal and oil produce are a result of their incomplete energy conversion. Therefore, natural gas is considered to be the cleanest burning fossil fuel.

For more information and fun games on natural gas safety, check out Sierra Pacific's Natural Gas Safety World at http://www.sierrapacific.com/kids_safety/gas/index.html.

And if you ever visit Centre County, you will find that the CATA buses around town are actually running on natural gas! Check out their website for more information on these environmentally friendly buses: http://www.catabus.com/accngprog.htm.

Little Lion Experiment:

Natural gas collects underground by seeping into and passing through reservoir rock (a layer of spongy rock). To keep the natural gas from moving or leaking to the earth's surface, a different layer of rock called cap rock (a layer of solid rock) exists above the reservoir rock. The combination of these different rock layers allows the natural gas to accumulate until it is ready to be used for energy needs.

This experiment will help you to understand the different ways that natural gas can be trapped underground. You will need these materials:

• sand
• clay
• two 8 oz. wide-mouth glass jars
• 16 oz. of water
• magnifying glass

Steps:

1. Feel the sand and clay with your hands. Do they feel different?
2. Examine the sand and clay with the magnifying glass. Do they look different?
3. Put the sand into one glass jar and the clay into the other glass jar. Fill each jar about 2/3 full.
4. Add the water to each jar to fill the remaining space.
5. Observe the water's behavior - Is it passing through the sand or clay to the bottom of the jar? Or is it sitting on top of the sand or clay?

The material that allows the water to pass through is acting like reservoir rock underground, which allows water to seep in. This is similar to how natural gas accumulates underground. The material that does not allow the water to pass through is acting like cap rock because it is stopping the movement of the fluid. This explains how natural gas can be trapped underground.