Monday, December 15, 2008
Some animals hibernate all winter, which is actually just a very deep sleep. This allows the animal to avoid the cold weather without having to move to a warmer climate. Hibernation 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. These animals get ready for winter by eating extra food and storing it as body fat, which is used for energy while hibernating. Some also store food to eat later in the winter. Some animals that hibernate include bears, skunks and chipmunks. Cold-blooded animals like fish, turtles, frogs, and snakes, find shelter in holes or burrows. There they spend the winter inactive, or dormant, which is similar to hibernation.
Other animals stay pretty active during the winter, but they must adapt to the changing weather. Many make changes in their behavior or bodies. For example, animals may grow new, thicker fur in the fall to keep warm. Food is often hard to find in the winter, so the animals must adapt to this as well. Squirrels, mice and beavers, gather extra food in the fall and store it to eat later. Other animals like rabbits and deer, spend the winter months looking for moss, twigs, bark and leaves to eat. Some animals even eat different kinds of foods as the seasons change. For example, the red fox eats fruit and insects in the spring, summer and fall. However, in the winter, the red fox cannot find these foods so it eats small rodents instead. These active winter animals must also stay warm through the cold months. They sometimes find shelter in holes in trees or logs, under rocks or leaves, or even under the ground. Some mice and squirrels even huddle close together to stay warm.
Some birds migrate or travel to other places where the weather is warmer or they can find food. Many birds migrate in the fall. The trip can be dangerous, so the birds often travel in large flocks. Birds can fly very long distance but most birds will migrate shorter distances. Other animals migrate, too, including bats, caribou, elk, and whales.
Little Lion Experiment:
This experiment will allow you to determine how much energy animals are saving while hibernating! You will need ice cubes, a small pot and a thermometer that goes down to 40°F (5°C) or lower. If you don't have a thermometer like that, then put a cup of cold water in the fridge, which is almost exactly the same temperature (41°F) as a deep hibernating animal. Put a cup of warm water on the kitchen table. Let both cups sit for 20 minutes. You will need a pencil and some paper to record your observations.
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 41°F. We'll call this the "deep hibernator time." Also note how much longer it takes to heat up to 60°F (the body temperature of an animal that is dormant). We'll call this the "dormant 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 98.6°F, 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 when the animal is hibernating) to the animal's body temperature. Similarly, the "dormant time" shows how much energy is needed to go from freezing to that animal's body temperature. The "human time" shows how much energy is needed to go from freezing to our body temperature. 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 41°F or 60°F instead of normal body temperature.
Saturday, November 15, 2008
Shanna from Altoona, PA, was helping her big sister prepare dinner one night, and she noticed that her eyes became really irritated when her big sister cut up an onion. She wrote in asking: why do onions make us cry? We will explore the answer to that question but we will also explore some methods that might minimize the eye irritation. Many people enjoy the taste of onions in their meals. In fact, the average American eats about 20 pounds of onions each year. Onions are healthy components of the human diet because they contain vitamins B and C, protein, calcium, and iron. They also contain quercetin (pronounced KWAIR-SUH-TEN), which is an antioxidant that works to neutralize harmful substances in our bodies that cause tissue damage and aging. In addition to being full of nutrients, onions are low in fat and sodium. However, if you have ever cut into an onion, it is likely that your eyes filled with tears because they became irritated just like Shanna described. But why does this happen? How can we enjoy the taste and benefits of onions without the tears? When you cut into an onion, an enzyme (a biomolecule that speeds up chemical reactions) is released into the air from the ruptured onion cells. This enzyme converts some of the proteins from the onion into sulfenic acids that then become a gas. These can then come in contact with your eyes. These acids contain sulfur compounds that are common eye irritants. The gas reaches your eyes and reacts with the water that keeps them moist. The eyes become irritated, and your brain reacts by telling your tear ducts to produce more water that helps keep the eyes protected. You may want to rub your eyes to help soothe the irritation, but this will only make the irritation worse since your hands may have onion juices all over them. Some people wear goggles to minimize any irritation produced when cutting onions, but some also try the different methods discussed in the Little Lion Experiment. Give each method a try to figure out which one works best for you so you can enjoy onions without any eye irritation!
Little Lion Experiment:
How can we enjoy the benefits and the great taste of onions without the tears? For this experiment, you will explore some methods that are thought to reduce the unpleasant eye irritation that occurs when cutting into an onion. You will need an adult present to help you with this, especially when cutting the onion. It is preferable to try these methods over 5 different days, but you can try each of these home remedies during the same time. Throughout each of these methods, keep track of whether your eyes were irritated when the onion was cut and try to determine which method works best for you.
- 5 small onions with the outer layers peeled away
- 1 lemon slice
- Slice of bread
- Bowl of water
- Access to a refrigerator
- Method 1: Put one onion into the refrigerator. After 30 minutes, take it out and cut the onion.
- Method 2: Put one onion into a bowl of water so that it is covered in water. Cut the onion while it is submerged in the water.
- Method 3: Put a lemon slice in your mouth. Then cut the onion (keeping your mouth open)
- Method 4: Put a bread slice in your mouth. Then cut the onion (keeping your mouth open).
- Method 5: Put some sugar in your mouth. Then cut the onion (keeping your mouth open with the sugar on your tongue)
Questions:Did any of these methods work to keep your eyes from being irritated? If so, which ones worked the best? Having the onion chilling in the refrigerator before cutting it, like in Method 1, is supposed to slow the release of the irritating gases. Keeping the onion under water while cutting it, like in Method 2, is supposed to keep the gases from even reaching your eyes. Keeping the sugar, bread, or lemon slice in your mouth while cutting the onion, like in Methods 3-5, is supposed to keep the gases from ever reaching your eyes since the food will absorb the gases. Try to remember these different methods each time you help out with the cooking at home. And remember to wash your hands after handling an onion since they will be coated in the onion's eye irritating compounds.
Wednesday, October 15, 2008
James from Altoona, PA, was helping his older brother wash some dishes in their kitchen sink recently, and he noticed that the dish detergent seemed to rinse off the dishes better with cold water than with hot water. He also observed that the hot water helped make the dish detergent foam more (i.e., produce more soap suds). He wrote in asking: how does the temperature of water affect the cleaning ability of soap? The use of soaps and detergents is part of everyday life (at least it should be!) so let's first discuss what soap is and how it works. You have probably heard the terms soap and detergent used to describe the various products that are used to clean clothes, dishes, hands, cars, or pretty much anything that needs cleaning. While they are very similar, they are slightly different. A detergent is a substance that cleans dirty or soiled surfaces. It is usually made from synthetic ingredients, which means the ingredients are not naturally occurring and are maufactured from different chemicals. Soap is a type of detergent and is usually produced from natural ingredients. Just from looking around your home, you probably have noticed that soaps and detergents are produced in many different physical forms - for example, there are bars, flakes, pellets, liquids and even tablets! Detergents and soaps contain a basic cleaning agent called a surfactant, which stands for surface active agent. Surfactants consist of molecules that attach themselves to the dirt particles of the dirty material that is being cleaned. The dirt particles are pulled out of the dirty material and are then held in the wash water until they are rinsed away. Most detergents contain a synthetic surfactant in addition to other chemicals that are added to improve the detergent's cleaning ability. Other ingredients that are added to detergents include perfumes, coloring agents and germ-killing or antibacterial agents. When it comes to temperature, hot or cold water is acceptable when cleaning with soap. The most important part of cleaning is using the soap or detergent! You need something that will pull the dirt particles from the dirty areas. Water alone will work OK, but water with soap will work even better.
Little Lion Experiment:
Like James above, you may notice that more soap suds are produced when using hot water. The reasoning for this begins with the fact that warmer water evaporates faster than cold water (the warmer water changes from a liquid to a gas faster than cold water). Soap suds or bubbles are formed more easily when the warmer water is evaporating. Colder water evaporates slower so it is harder to make soap suds. With this information, do you think bubbles will last longer in hot or cold water? This experiment will help you determine the answer!
- Two large bowls (or tubs)
- Rubber gloves
- Tablespoon measuring spoon
- Access to cold and hot water (from your faucet is OK)
- Stop watch
- Some type of soap (you can use dish detergent, laundry detergent, hand soap, etc.)
- Fill one bowl with warm water and the other bowl with cold water.
- With the gloves on, add one tablespoon of your soap to each bowl.
- Use the tablespoon to mix the soap into each bowl for 30 seconds.
- After mixing, start the stop watch and observe how long the bubbles remain in each bowl. Did the bubbles last longer in the warmer water or the cold water? Why do you think this is so? With the faster evaporation of the warm water, the bubbles may form more quickly than the cold water but that also means that they will disappear sooner too. The slower evaporation of water means that the bubbles may take longer to form but they will also last longer once formed.
Monday, September 15, 2008
Laura from Hollidaysburg, PA, was recently helping her parents clean her home, and she noticed how much dust there was on the tables, in the air, and coming from the couches! She wrote in asking: Where does dust come from and what happens to it when we breathe it in? About 21% of the air we breathe is actually oxygen, while the remaining air consists of other gases (e.g., nitrogen, argon, carbon dioxide). However, the air also consists of dust, tiny animals, and other stuff! Dust is defined as dry, solid particles that are less than 0.0625 millimeter in diameter, which is smaller than all grains of sand! Most dust is composed of mineral matter that originated from bare soil, plowed fields, river flood plains, and floors of desert basins. Dust also comes from ocean spray, smoke and ash produced by fires, decaying organic materials, and volcanic eruptions. The wind actually lifts up the dust particles and easily carries them long distances around the earth! The dust in your home can also be made up of dust, pollen, mold, sand, skin flakes, and pet dandruff. These air particles are actually the most common causes of allergies or asthma. Humans and animals can also act as carriers of dust and air particles because the air particles can cling to their skin or clothes. When you breathe in, you are also breathing in dust or air particles. Some of these air particles will get caught in your nose hairs, some will get caught in mucus in your airways, and some will make it into your lungs. However, don't worry too much about this, because most of what you breathe in will cling to the hairs on the inside of your nose. These hairs act as a filter, which works to trap the inhaled air particles inside your nose to keep them from traveling into your respiratory system. The hairs usually trap particles that are less than 5 nanometers in size (that is approximately 0.000005 mm!). Aside from the many nuisances of dust around your home, dust actually contributes to some beautiful sunsets and sunrises. That's right, dust is what makes sunsets and sunrises so pretty! The intense red and orange colors of the sky at sunset and sunrise are mainly caused by the scattering, or reflection, of sunlight off air and dust particles. So the next time you are cleaning your house or enjoying a beautiful sunset or sunrise, think of the dust that is contributing to these everyday events.
Little Lion Experiment:
This experiment will allow you to observe the types of air particles you breathe regularly.
- 6 index cards
- A pen
- 6 pieces of string
- tape (scotch, masking, duct, or packing tape is good)
- A magnifying glass
- A ruler
- Cut squares into the center of each index card. Try to make all the squares the same size (e.g., about 2'' by 3'').
- Choose 6 locations within your home that you want to hang the air particle collectors. Some places to hang your air particle collector include: above your bed, on the inside or outside of a window, near a heating vent or air conditioner, above the cooking stove, on a wall near the floor or ceiling, on your main entry door, and under a tree.
- Write down the locations on the index cards so that each index card has a different location on it
- Write the starting date on each index card
- Cover the window on the index card with the tape so that the stick side up or out.
- Attach string to each index card, and then hang the cards at the appropriate locations.
- Wait a few days and then take the index cards down without touching the tape. Make sure to note the date. Which location had the most air particles collected? Were these locations inside or outside? Why do you think this is so? Think about where air is moving, and where the air particles could be coming from. Use your magnifying glass to examine the air particles up close. Can you recognize any common air particles?
Friday, August 15, 2008
Have you ever forgotten to put on sunscreen, then regretted it the next day? Many of us know what sunburns look like, but do you know why we get them? Let's start with some background information on how our skin responds to light. Cells called melanocytes in the inner part of your skin produce the pigment melanin, which is what gives color to our skin. Believe it or not, we have about 1000 to over 2000 of these cells per square millimeter of skin! If you have dark skin, that means that your melanocytes are programmed to make a lot of melanin all the time. If you have lighter skin, then you have the same number of melanocytes, but they don't produce as much melanin. If you are albino, then your melanocytes cannot do their job because they are lacking an enzyme (a piece of cellular machinery) which is needed to make melanin. On most days, we do not get exposed to enough sunlight to cause us to develop a suntan. However, a nice day spent at the beach is much different. The darker your skin is, the more light you can withstand without having to boost your melanin production. When your body senses that you need more melanin to protect you against harmful UV rays (UV stands for ultraviolet), your melanocytes kick into high gear and you get a suntan. However, if you stay outside for too long, especially without sunscreen, then your body can't make melanin fast enough to keep up with the amount of UV exposure. This is what causes a sunburn. A sunburn can be thought of as a "clean-up crew" of various blood cells being sent to repair the damaged area. This increased blood flow is what causes sunburns to appear red and feel warm to the touch. Starting to sound a bit like a sunburn? There's one thing missing: why does sunburned skin tend to peel? Your body does its best to repair the UV damage, but if the damage is too great, then the unrepaired cells will simply shed or flake off to make room for new healthy cells to replace them, which allows the sunburn to heal. You may have heard about the relationship between sunburns and skin cancer. Even though the "clean-up crew" and the skin cells themselves usually undo the harmful effects of UV, they may not always do a perfect job. This would allow damaged cells to stay in the skin. Most sunburns will not lead to cancer, but a tiny fraction of them can if they damage a cell's ability to stop dividing. This is why it is so important to wear sunscreen in order to avoid over-exposure to UV light. There are two types of sunscreens: those that reflect UV light (like tiny mirrors) and those that absorb it like melanin does. Everyone gains extra protection from wearing sunscreen, but if you are fair-skinned or albino, it is especially important that you wear it. Remember to put it on around 30 minutes before you go outside so that it has time to stick to your skin. Otherwise, it will rub off on the grass or wash off in the water. [Safety note: some people (especially those with sensitive skin) have allergies to PABA, a chemical in some sunscreens. So if you have sensitive skin, you may want to consider buying a PABA-free sunscreen]. For more information, visit http://travel.howstuffworks.com/sunscreen.htm
Little Lion Experiment:
While UV light is harmful in some respects; we need it to stay healthy! This is because our bodies need about 10 to 15 minutes of daily UV exposure to make vitamin D. In fact, many reactions are activated by light (various kinds of light, not just UV). To see how important light is for living things to survive, obtain two small planter pots. Plant about 5 evenly-spaced seeds in each pot. If you cannot purchase seeds at your local hardware or gardening store, you could use seeds from a fresh tomato. Place one pot in front of a sunny window and place the other pot in a dark area (a cabinet would do, with your parents' permission). Remember to water the plants every few days (specific instructions can be found on the seed packet). Check on the plants over the next couple of weeks to compare the seedlings in the light versus those in the dark.
Tuesday, July 15, 2008
The pencil eraser works based on the friction developed between the eraser and the paper. Friction is what causes your hands to heat up when you rub them together. When you rub two objects the roughness of their surfaces contact each other and rub against each other causing friction. A simple pencil is made of a combination of wood and finely ground graphite and clay, mixed with water and pressed together at high temperatures into thin sticks or rods. Graphite is a mineral composed of an element called carbon, and it is black in color. There are also mechanical pencils that need rods of graphite to function like a pencil. You may have heard that pencils are made of lead, but that is actually a misunderstanding that is based on the initial thoughts of those that first discovered graphite - they believed it to be lead, which was not the case at all. However, many still refer to graphite in pencils as lead. Graphite particles are arranged in layers or sheets. A pencil mark consists of graphite particles that have peeled off from the pencil point onto the paper. These particles have an angular, gritty look to them when viewed under a microscope. When the pencil is used on a sheet of paper, the graphite particles lie slightly below the surface of the paper, interlocked between its fibers. A single rub using an eraser sufficiently soft to reach between the fibers will pick up most of the graphite particles. Looking at the eraser you can see undamaged graphite pieces sticking to the surface. An effective erasing material scratches the paper surface, producing the familiar small spindles of rubber or eraser material, which wrap up the graphite particles. When you look at these under an optical microscope at 200 times magnification (200x), these look like roly-poly puddings studded with graphite raisins.
Little Lion Experiment:
Erasers come in a variety of colors: white, pink and gray are some of them. Sometimes the color difference is because of a dye or because the eraser is made of a different type of rubber. Go around your house and see how many types of different erasers and pencils you have. For example, compare number 2 pencils with a number 3 pencil. Also, if someone in your home has a mechanical pencil, you can purchase different types of pencil leads (like hard black or soft) or they might have different leads you can use. The bright-colored erasers (like purple and yellow) are usually white erasers in disguise! You can also use erasable pen as a pencil type. See which one of these works best with different types of pencils and ink. Can you erase the ink with a pink or white eraser? Is there one eraser that works for all lead types? Knowing what you know about how erasers work, why do you think certain erasers do not work with other types of pencil lead and ink?
Sunday, June 15, 2008
It is almost officially summer! And that means plenty of sunshine and hot temperatures. With all the sun and heat, you will likely be drinking more water to keep hydrated. Most people prefer their water to be "ice cold", which just means there is ice in the glass to keep it cold. But, you may have noticed that ice doesn't just sink to the bottom of the glass - have you ever wondered why? This month we will explore that very question! The meaning behind this mystery lies in the different properties of solid and liquid water. Nearly every solid, if placed in its liquid form, will sink to the bottom. Luckily for us, the properties of water are different. Unlike most other substances on Earth, the solid form of water floats on the liquid form. This is caused by the change in density, which is defined as the amount of mass in a volume. With the exception of water, most substances on Earth become denser as they become colder. The solid ice will float because its density is lower than that of water. It is about 9% less dense than water. The denser water sinks to the bottom forcing the less dense ice to the surface. What makes water molecules different from other molecules is that they attract each other in an organized fashion. As the water cools, the molecules begin to bind to each other, forming a hexagonal pattern (shape that has six sides). Water is at its densest point at 4 degrees C. After that point, the water molecules move very slowly and attract to each other. In most substances, the molecules are more tightly packed together in solid form. But in ice, the hexagonal pattern of the attracting water molecules leaves empty spaces. This is why water expands when making ice cubes. The empty space between the hexagonal shapes makes the solid form less dense than the liquid form so that it floats to the top. Thanks to this oddity of physics, the water in our oceans and seas remain in liquid state. If the solid form of ice happened to be denser than water, the ice would sink to the bottom. If this happened, the ice on the bottom would begin to freeze up toward the surface. Eventually, nearly all the water on Earth would become solid ice and never melt. Luckily, ice floats and remains on the surface so that the water underneath remains in liquid form.
Little Lion Experiment:
This experiment will demonstrate that ice does float in most liquids, but you will also test other solid materials to see if they float, too.
- 4 ice cubes
- 4 small rocks
- 4 small magnets
- 4 quarters
- 4 glasses
- 4 different liquids (e.g., water, soda pop, salt water, and milk)
- Put each liquid in its own glass.
- Drop one of each solid material (i.e., ice cube, small rock, small magnet, quarter) into each glass.
- Observe what happens. Did any of the materials sink to the bottom or float to the top of all the glasses? Did some sink to the bottom of one glass but float to the top of another glass? What can you conclude about the solid materials? What can you conclude about different liquids used? Keep trying different solid materials and different liquids to see how they compare!
Thursday, May 15, 2008
A-choo! With all the flowers blooming, it is no wonder that hay fever is upon us - that is, it is allergy season! Kaylee from Altoona, PA, who suffers from seasonal allergies writes in to ask about allergies. We are all familiar with the coughing and sneezing, but what exactly are allergies and what causes them? Every day, our bodies are in constant contact with potential threats. These include pathogens (harmful microorganisms), pollution, and a host of other dangers. However, most of the time, we aren't even aware that anything nasty has entered our bodies. How are we able to combat these invaders so effectively? We have our immune system to thank. Immune cells called lymphocytes (pronounced lim-fo-sites) patrol all parts of the body looking for foreign molecules and microorganisms (tiny living things, like bacteria). Each lymphocyte is programmed to recognize a specific pathogen. Anything which is not part of our body is classified as "non-self" while every one of our own cells is termed "self." In short, the role of the immune system is to attack and destroy any cells it finds that are "non-self." We also have sensors in our bodies which can detect the presence of harmful chemicals. Have you ever walked by a car and coughed or sneezed as you smelled the exhaust? This is because you have sensors in your nose, throat, and lungs that tell your brain that you have inhaled dangerous fumes, which you need to get rid of right away. So, your body sends the signal to cough and sneeze until you push out all of the fumes. This signal is sent by a chemical messenger called histamine. If you have allergies, or know someone who does, then you might agree that the symptoms of allergies are kind of like a huge overreaction to the car fumes, except without the car! People with allergies react as if they have inhaled something toxic when in fact they have just inhaled normal everyday things like pollen and dust that are not harmful (these everyday substances are called allergens). This occurs because some of their lymphocytes are programmed to recognize the allergen as a harmful substance even though it is not. So, when the lymphocytes find an allergen floating around in your body, they trigger histamine to be released which causes the common allergic symptoms such as watery eyes, runny nose, sneezing and coughing (these are all ways to flush out the allergen). Histamine also triggers local swelling near the pathogen or allergen, and so it can cause narrowing of the airways (nose and throat) when you inhale pollen or dust in order to prevent more of the allergen from entering the lungs. Unfortunately, that makes it harder for the person to breathe. Here's an interesting fact: histamine is also responsible for asthma - can you see the connection? So how can we treat allergies? The primary method to prevent allergic symptoms is to treat the person with antihistamines, which have been used since the 1930s to control allergies. The medicine does not affect the lymphocytes, but rather it just prevents histamine from triggering its bothersome symptoms.
Little Lion Experiment:
This experiment will demonstrate how allergens or pathogens may stick to the lining of your nose or throat to cause sneezing and coughing.
- An empty toilet paper roll
- Running water from your sink
- Black Pepper
- Confectioner's Sugar
- Jimmies or sprinkles
- Run water over the inner surface of the roll until it is wet but not soggy.
- Hold the tube sideways in one hand over a sink (so as not to make a mess) and carefully place the pepper on the inside of the tube
- Rotate the tube until it is coated with the pepper.
- Repeat steps 2 and 3 with the salt, sugar, and jimmies
Did all of the substance stick? If the substance does not stick, then that is a pretty good indication that it is large enough that it would not stick to the lining of your nose or throat. If it sticks, then it is probably something that would get trapped in your airways if you were to inhale it. Now, slowly turn the tube until it is vertical. To simulate coughing, quickly shake the tube or bang it against the inside of your sink. See which kinds of substances come out the most easily. To simulate sneezing, blow air through the tube and see what comes out in your sink. The body also uses mucus in your airways to help carry foreign molecules out (like the sea carries shells to the shore). Pour a small amount of oil into the tube and see if it takes out some of the remaining particles.
Tuesday, April 15, 2008
The water cycle is a term used to describe the continuous movement of water in and around the Earth. About 70% of our Earth is covered by water, which amounts to approximately 333 million cubic miles! So that’s a lot of water in constant operation – but how is it in a constant cycle?
Two major components of the water cycle are evaporation and condensation. Evaporation occurs when a substance goes from the liquid to the gaseous state, and condensation occurs when a substance goes from a gaseous to a liquid state. These processes happen on Earth with the help of the sun. The sun heats the surface of water causing it to evaporate into water vapor (gaseous water), which rises into the atmosphere. This water vapor then cools and becomes clouds, which eventually condense into water droplets. Depending on the temperature of the atmosphere, the water then precipitates (falls back to the Earth’s surface) as rain, sleet, hail or snow. Some of this precipitation falls on trees or other plants and can evaporate again into the atmosphere. The precipitation can also continue to the ground, and now the water is considered runoff water. This runoff water can then get into the ground and accumulate where it is eventually stored in aquifers, which are large, natural storage tanks of groundwater that can be used later if needed. The runoff water can also form or add to lakes and streams, which can also then freeze into snow caps or glaciers. Water that falls to the ground and stays in the soil ends up evaporating and returning back to the atmosphere – you can see how this is a continuous cycle! The water in aquifers, though, can accumulate there for thousands of years. Aquifers are actually our major sources of drinking water.
So consider the long journey water has taken the next time it rains, snows, hails or sleets. Maybe it end up as your drinking water or maybe it will end up in your local water reservoirs. Perhaps, it will just evaporate back into the atmosphere to come back to the Earth’s surface as rain another day.
Little Lion Experiment
This experiment will allow you to create a small-scale model of the water cycle using common items found around your house. You will need: plastic wrap, a large bowl (preferably one that is clear), a weight (a paperweight will work), small container (a clean, empty yogurt cup works well), a rubberband or piece of string, tap water, paper and pencil. You will also need access to sunlight.
Steps: 1) Place the small container in the middle of the large, clear bowl so the opening of the small container is up. 2) Fill the bowl with some water (at most half full) but be careful not to fill the small container inside. 3) Cover the bowl with plastic wrap. 4) Fasten the plastic wrap around the bowl’s rim with the rubberband or string. 5) Put a weight on top of the plastic wrap in the center. 6) Put the demonstration on a window sill or somewhere that it will be in contact with the sun. 7) Record your observations of the experiment every 10 minutes on your paper (you should conduct this experiment for at least an hour).
What did you observe? Hopefully you saw that the heat of the sun evaporates the water, which rises, condenses on the cool plastic, and falls into the small container similar to how rain falls. Now that you know how to make your own model of the water cycle, change some of your materials in the experiment. For example, use salt water instead of tap water. Or, you could use ice water (a mixture of water and ice chips) instead of tap water. Were you still able to observe the water cycle?
Saturday, March 15, 2008
The human ear consists of the outer ear, middle ear, and inner ear which is fairly deep inside of your head. The middle ear is separated from the outer ear by the eardrum allowing the air trapped inside the middle ear not to come in contact with the air outside of your head. When you experience a change in air pressure by getting closer to or further from the ground, your ears will occasionally "pop" to adjust the pressure of the air that is caught in your middle ear so that it matches the air pressure outside of your head. This is done by quickly opening the Eustachian tubes, which connect the middle ear to the back of the nose, in order to let air rush in or out of the middle ear as needed.
The most common place for someone's ears to "pop" is on an airplane, but it can also happen with smaller changes in altitude (the height above the Earth's surface), like when you are driving up or down a mountain. The air closer to sea level is at a higher pressure since it is being compressed by the weight of all of the air above it. As you climb to higher and higher altitudes, the air pressure decreases. Some people may find the popping of their ears to be annoying, but if your body didn't do this, then the pressure on one side of the eardrum would be higher than on the other side which could bend your eardrum slightly and compromise your hearing.
If your plane is taking off, then you are going to an area with lower pressure so the high-pressure air in your middle ear will push outwards on the eardrum. When your ears pop, air rushes out. If you are coming in for a landing, then you have low-pressure air in your head (from when you were at a high altitude) and high-pressure air outside pushing inwards on your eardrum. When your ears pop, air rushes in.
One way to make this pressure equalization more comfortable is to do it yourself by swallowing or yawning frequently rather than waiting for your ears to pop by themselves. These methods work because swallowing and yawning cause the Eustachian tubes to open briefly. This is why many people choose to chew gum when their plane is taking off or landing (chewing gum or sucking on a hard candy makes you swallow more than if your mouth were empty).
Little Lion Experiment:
If someone has a blocked or oddly-shaped Eustachian tube, then their ear will fail to pop as their plane is landing. This creates a small vacuum in the middle ear. Fluid then rushes into the middle ear to increase the outward pressure until it equals the inward pressure from the surrounding high-pressure air. This experiment will help you observe the effects of having a blocked Eustachian tube. You will need: a small plastic cup (if possible, use a clear cup), a bowl with a flat bottom, and some water.
- Fill the bowl with about an inch of water.
- Turn the empty plastic cup upside-down and squeeze it until it bends inward.
- Place the bent cup in the water.
- Being careful not to let the lip of the cup rise above the water level, slowly squeeze the creases in the cup outwards so that the cup returns to its original shape.
By doing this, you are creating a small vacuum. So, the pressure inside the cup (which pushes outwards) is lower than the pressure outside of the cup (which pushes inwards), and this pressure difference is what pushes the water from the bowl into the cup until the two pressures are equalized. As a side note, the same principles of air pressure explain how straws, turkey basters and a variety of other objects are able to move liquids against gravity.
Friday, February 15, 2008
Cheese is probably in a lot of your favorite foods especially if you like pizza, lasagna, enchiladas, or macaroni and cheese. Some say that any food tastes better with cheese, but what is cheese? Cheese is essentially a preserved form of milk, which usually comes from cows but can also come from goats or sheep. About 80% of milk in its natural state is water. Cheese is basically formed when the water from milk is removed and the curds (the remaining solids) are compressed, which means the solids are squeezed or pressed together. However, cheese makers can do many different things to the curds to enhance the flavor and color to make the various kinds of cheese that you are used to. Think about how many types of cheese you already know about. It’s no wonder that cheese can be classified according to its age, country of origin, fat content, dairy content, texture, manufacturing methods, and more.
Fresh cheeses like cream cheese, ricotta, cottage cheese, and mozzarella, are the most basic cheeses because they are uncooked, unaged and sometimes still contain whey (the liquid part of milk). These cheeses must be eaten soon after they are made because they spoil quickly. Soft-ripened cheese like Brie is created from the introduction of a mold during the ripening process, or aging process. Mold is a form of fungus, which gives the cheese more flavor. Blue-veined cheeses are similar and develop blue or green streaks of harmless, flavor-producing mold throughout the interior. Washed-rind cheeses like Limburger are washed in a liquid (i.e., salted water, wine, or beer) that encourages the growth of bacteria and mold during the ripening phase, which gives the cheese a very strong smell and taste. Cheddar is an uncooked, pressed cheese, which means its curds have not been heated and the cheese has been pressed to give it a very compact, dense texture and flavor. Cooked, pressed cheese like Parmigiano-Reggiano and Provolone has its curds heated before being pressed. Processed cheese (like American, Velveeta, and spray cheese) is not technically a cheese but is actually a byproduct of the cheesemaking process. Byproducts are products made during the manufacture of something else. Processed cheese can be made with scraps of cheese but can also include whey, cream, water, dyes, gums and other ingredients. This type of cheese lasts a long time and melts easily.
So, how can some cheeses, like cheddar, be both yellow and white colors even though they are the same type of cheese? Cheese used to be different shades of white, yellow or orange, depending on when it was made during the year and also what the cows had eaten. For instance, in the spring/summer, cows eat fresh grass and other plants that contain beta-carotene and vitamin D which results in cheese that is yellow in color. In the winter, cows eat hay, which caused cheese to be pale in color. Cheese that is yellow in color is generally more desirable, so cheesemakers now dye their cheese.
Little Lion Experiment
This experiment will expose you to the many different kinds of cheese available at your grocery store or even in your own refrigerator! Much like there is a vegetable section, most supermarkets will have a section totally devoted to cheese. The next time you go to the supermarket with your parents, see if you can browse the different kinds of cheeses there. Then ask your parent if you can try 5 of these different cheeses (you will probably have to buy the cheese to taste it). Try to pick at least one kind of cheese that is two different colors (for example, yellow cheddar and white cheddar). Taste each kind of cheese and decide if you think the cheese is soft-ripened, blue-veined, washed-rind, uncooked-pressed, cooked-pressed, or processed. Try to pick cheese that you know you enjoy and also pick some cheese that you have never had. Check your refrigerator before you go to the store, too, to see what kinds of cheese you might already have! For the cheese that is two different colors, decide if you think each cheese sample tastes the same or different. Do you think one of those cheeses was dyed? Tasting the different kinds of cheese will allow you to identify the kinds of cheese that you like and dislike. You will also be able to explain to others why the cheeses can taste so different!
Science Lions is a Penn State University student volunteer organization dedicated to fostering science and engineering interest in students in kindergarten through grade 12. To learn more about the Science Lions and to submit a question for Ask Science Lions, visit http://www.clubs.psu.edu/up/sciencelions/.
Tuesday, January 15, 2008
You may not realize it, but there are many different types of thermometers around you. A thermometer detects or measures a change in temperature. Some thermometers are better at accurately measuring the temperature of something - these would be used for measuring your body temperature to see if you had a fever, measuring the temperature outside, or measuring the temperature of meat to make sure it is cooked thoroughly. Others are better at controlling the temperature at a set level - these would be utilized in refrigerators, ovens, and furnaces. However, both types of thermometers work differently.
The bulb thermometer is the common glass thermometer that you may be most familiar with. Perhaps you were sick and used this type of thermometer to see if you had a fever. It contains a fluid, which in principle changes its volume relative to its temperature - this simply means that the fluid will occupy less space when it is cold and it will occupy more space when it is warm. So when the thermometer is in contact with something warm, the fluid will expand and rise up the glass column where the corresponding temperature can be read. Mercury used to be the fluid of choice for these types of thermometers, but nowadays most bulb thermometers use a non-mercury fluid since mercury is toxic
A bimetallic strip thermometer is good at controlling temperature and like its name suggests is made of two different metals (usually steel and copper). The two metals are bonded together and either left as a strip or coiled. The metals expand at different rates as they are heated. The different expansions cause the flat strip to bend one way if heated or bend the opposite direction if cooled below its normal temperature. When the strip is bent, it can make contact so that a current related to the temperature can flow. The temperature can be controlled by adjusting the size of the gap between the strip and the contact.
These types of thermometers work very differently but are equally important. Try to identify which type of thermometer is used in the many different devices that you encounter in your everyday life that utilize temperature to function.
Little Lion Experiment:
In this experiment you will make a simple bulb thermometer, which will mimic how a typical bulb thermometer works.
- Clear, plastic bottle (water bottle would work!)
- Cold water
- Rubbing alcohol (make sure to get help from an adult with this!)
- Clear, plastic drinking straw
- Modeling clay or silly putty
- Food coloring
- Fill the bottle with equal parts water and rubbing alcohol until the bottle is 25% full.
- Add a few drops of food coloring.
- Put the straw in the bottle, but don't let it touch the bottom.
- Use the modeling clay to seal the neck of the bottle so the straw stays in place (i.e., keeping the straw from touching the bottom of the bottle).
- Hold your hands on the bottom of the bottle.
What happened? Did the liquid mixture move up the straw? Why do you think this happened? When you put your hands on the bottle, you heated up the water. As we discussed above, liquid mixtures will generally expand when they are heated. So as your hands heated the water/alcohol mixture, the mixture expanded and could no longer fit in the bottom of the bottle causing it to move up the through the straw. Try sitting the bottle in the sun. Did this cause the mixture to move up the straw more?