Heat Energy Movement and Heat Loss

Some of you from the Altoona area had recently read about why it feels colder on a windy day than on a day without wind. A few months ago, we had also discussed how it feels warmer on a cloudy day. So what is the science behind these questions, both of which seem to involve heat. It has a lot to do with the way heat moves from place to place, or as scientists call it – heat transfer. One of the basic facts in nature is that heat (which is a form of energy) always moves from a hotter object towards a colder object.

Heat can move in several ways from one place to another. Let us think about the different ways now. Do you know that when you touch a cold wall or a window, your warm hand is actually losing heat to the window glass? This form of heat movement is called conduction. This is the same manner heat moves from the stovetop to the kettle or to a soup pot. Conduction is heat movement by contact. Here the hot body has to touch the cold body for heat transfer by conduction.

But remember the cold wind story, there the heat is moved away from you by convection. Here there is usually a fluid medium, it can be air or water usually which carries the heat away from the hotter body. This is the same way how heat comes into your room through baseboard heaters when hot air is blown into the room. Convection involves another medium, usually air or water, transferring the heat. When cold air leaks into a house, it is convection which is to blame for our heat loss.

A third form of heat transfer, which does not require any medium or contact to occur, is radiation. Here the heat energy travels in the form of waves which can go through even vacuum. This is how the heat energy comes to earth from the sun, across millions of miles in the space. This is also how we lose heat from a closed car in winter, when it is left parked overnight. On a windy day, the wind can add to the loss of heat by taking heat away from the glass surface of windows and the body of the car. Radiation is also why we like to open our curtains on a sunny day in winter, to let warmth in through the glass windows.

One of the best examples of a man made object that tries to prevent heat loss is the thermos flask. If you ever get a chance to see one, you should examine it closely. One of the big benefits of a thermos flask is that it keeps colds things cold or hot things hot. You can read more about it at: http://home.howstuffworks.com/thermos.htm . Also look up the words thermal insulation on the internet and find out what it means.

Little Lion Experiment
We will learn how different forms of heat transfer take place. Caution: We will NOT be using any kind of stove or electric heaters to do these experiments. We will be using hot water from the tap in the house to provide heat to some cold objects. But even with this you need to be extra careful not to spill any on yourself or get scalded. Be very careful and use only small amounts in small mugs. 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. Keep plenty of washcloths or paper towels around to take care of spills.

You will need:
1) Cold water
2) Hot water
3) A coffee mug or a cup to pour with
4) A small bucket or a quart saucepan
5) Aluminum foil
6) Plastic wrap
7) A newspaper
8) Two or three Hershey’s kisses kept in a cold place for an hour (yummy chocolate!)
9) A pencil and a small notepad to make notes.

Conduction Experiment Steps:
1) Keep a piece of aluminum foil (10 inch by 10 inch) larger than your hand over a cold glass window and keep your hand on the foil to feel the temperature.
2) Repeat the same step with a newspaper and also with your bare hand (only for a few seconds). Note the case when it felt coldest.

Radiation Experiment Steps:
1) Fill up hot water in a coffee mug almost till the top. Carefully cover the top with plastic wrap till it is snug and tight, tape the overhanging wrap around the cup if possible.
2) Keep the mug inside a bucket/saucepan.
3) Carefully place an unwrapped Hershey kiss on top of the plastic wrap.
4) After 5 minutes, check the condition of the chocolate, has it slightly melted?
5) Try the same experiment, but instead of the plastic wrap, cover the coffee mug with aluminum foil, making sure that the shinier side of the foil faces the hot water. And use a new chocolate.
6) Try the same experiment with newspaper taped to the top of the mug. Observe if any melting occurs.

Think about how the shiny side of the foil acts as a mirror to the radiation heat and prevents it from coming out of the mug. Final tip: you can probably eat the chocolate from the plastic wrap and the foil experiments, but the chocolate from the newspaper experiment may not be clean. Throw it away. Instead of chocolate you can also use small piece of candles/wax.

How Do Animals Survive the Winter?

With the winter months upon us, Julia from State College, PA, writes in to ask how animals survive during the colder months of winter. She asks does the cold weather affect them? She is also curious about the food they eat during the winter months.
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.

Why Do Onions Make Us Cry?

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.

Items Needed

• 5 small onions with the outer layers peeled away
• 1 lemon slice
• Slice of bread
• Sugar
• Bowl of water
• Access to a refrigerator
• Knife

Procedures

1. Method 1: Put one onion into the refrigerator. After 30 minutes, take it out and cut the onion.
2. 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.
3. Method 3: Put a lemon slice in your mouth. Then cut the onion (keeping your mouth open)
4. Method 4: Put a bread slice in your mouth. Then cut the onion (keeping your mouth open).
5. 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.

How Does Temperature Affect the Cleaning Ability of Soap?

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!

Items Needed

• 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.)

Procedures

1. Fill one bowl with warm water and the other bowl with cold water.
2. With the gloves on, add one tablespoon of your soap to each bowl.
3. Use the tablespoon to mix the soap into each bowl for 30 seconds.
4. 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.

What is in the Air We Breathe?

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.

Items Needed

• 6 index cards
• Scissors
• A pen
• 6 pieces of string
• tape (scotch, masking, duct, or packing tape is good)
• A magnifying glass
• A ruler

Procedures

1. Cut squares into the center of each index card. Try to make all the squares the same size (e.g., about 2'' by 3'').
2. 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.
3. Write down the locations on the index cards so that each index card has a different location on it
4. Write the starting date on each index card
5. Cover the window on the index card with the tape so that the stick side up or out.
6. Attach string to each index card, and then hang the cards at the appropriate locations.
7. 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?

Why Do We Get Sunburns?

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.

How Does a Pencil Eraser Work?

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?