Nora from Altoona, PA, wanted to know more about hair. She wrote in asking several questions about hair including: Is human hair different from animal hair? What is hair made of? Why is hair so different among the people she knows? These are all great questions about hair! So we will first learn some background about hair (e.g., structure, physical properties, and growth patterns), and then we’ll answer the questions.
We generally just think of humans having hair on the head and face but all land mammals have hairy skins. Humans are actually covered all over their bodies with hair except for the palms of the hands, soles of the feet and lips. Even though there is less visible hair on humans compared to other mammals (e.g., cats, dogs, chimpanzees), a square centimeter of human skin actually contains a greater number of follicles (or hair producing sites) than the same sized area of other mammals. The hair all over our bodies is less visible because we have lost the requirement for insulating our bodies, while mammals have not. Hair has more cosmetic value for humans but it also is for protection. For example, hair around the eyes, ears and in the nose prevent dust, insects and other debris from entering those organs where they could cause damage.
A hair is an outgrowth of the epidermis, or outermost part of the skin. Hair consists of the hair follicle and the hair shaft. The hair follicle is the point from which the hair grows, and it is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is actually where the pigment, or color, of hair is produced. This pigment is called melanin and is carried upwards into the inner part of the hair as it grows. The hair shaft is the part of the hair that can be seen above the scalp. It consists mainly of dead cells that have turned into keratins (a special protein that is resistant to wear and tear, which is made up of very large molecules) and binding materials with small amounts of water. The center part of the hair shaft is called the cortex, while the outer layer is called the cuticle. If one thinks of the hair shaft like the trunk of a tree, then the cuticle would act as the bark protection the inner cortex where all its moisture lies. If the “bark” of the hair is well cared for, then the whole hair should remain in good condition. However, if the “bark” of the hair is damaged or stripped, then the exposed center of the hair may break.
Now that we know a little more about hair, we can answer Nora’s questions. We learned what hair is made of, but why is hair so different among the people she knows? In general, the type of hair you have is inherited from your parents. It’s actually possible that your hair type might be determined by the part of the world in which your ancestors came from. Nora also asked about animal and human hair differences. The coating of animal hair insulates just like human hair, but it also provides protection from rain. The growth pattern of hair for animals is more synchronized (or growing together), while human hairs tend to grow independently. Humans get their hair cut to their individual desires, while animal hair grows to a certain point and sheds (falls out) at certain times during the year (i.e., shedding often occurs when the coat is too heavy for the weather conditions related to the season) to be replaced by new hair when needed. Human hair is generally the same texture, but animals usually have two textures: there is a coarser top layer of hair and a finer layer (called under fur). These different textures help to insulate the animals. Another feature of hair on mammals is that sometimes their hair color blends with their surroundings, which provides protection against most predators.
Little Lion Experiment
As we have just learned, hair serves the purpose of body insulation and protection from other outside elements for both humans and mammals. This experiment will allow you to determine if the shade of human hair has an effect on its ability to insulate the human body.
You will need: access to dark colored hair and light colored hair (see if you can have the scraps of hair left behind at barber shops or hair salons), a scale (something that can measure in ounces), gloves, an apron or shirt that can get dirty, six paper lunch bags, two thermometers, a heat lamp or constant light source, ruler, stop watch and materials to record your results.
Steps
1) Collect the two different colors of hair from a barber shop (you will need approximately 6 ounces in weight of each color);
2) With gloves and apron on, put 1 ounce of each hair color into two different paper bags (remember to keep the hair colors separate);
3) Label the bags according to the type of hair inside and the weight;
4) Close the bags by folding the top down;
5) Repeat Steps 2-4 but put 2 ounces of each hair color into two more different paper bags;
6) Repeat Step 2-4 but put 3 ounces of each hair color into the last two paper bags;
7) Place the thermometers on a table about 15 inches apart from each other;
8) Put the 1 ounce bag of dark hair on one thermometer, and put the 1 ounce bag of light hair on the other thermometer;
9) Place the heat lamp approximately 10 inches in front of the bags and also try to center the lamp (center the lamp so that the light is evenly hitting both bags of hair);
10) Record the temperature changes every two minutes over a total of 10 minutes (do not leave the experiment while in progress);
11) Repeat Steps 8-10 for the other weights of samples;
12) You may want to repeat the experiment more than once for each weight of hair but that is up to you!
Look at your results. How do the temperatures recorded from under the dark hair samples compare to the temperatures under the light hair samples? Hopefully, your experiment was a success and you determined that the dark hair samples showed the greatest temperatures, whereas the bags containing the light hair showed the lowest temperatures. What does this mean exactly? Similar to light and dark colored clothing, dark hair absorbs heat better than light hair. So on sunny days, dark hair will prevent heat from passing through to your head while light hair will allow more heat to pass through.
Sunday, March 15, 2009
Sunday, February 15, 2009
How Does Soundproofing Work?
Charles from Altoona, PA, has an older brother that plays the trumpet. His brother practices the trumpet in the bedroom next to his. He wrote in asking if it was possible to block out the sound so that he does hear the trumpet while he’s in his bedroom. Charles is essentially asking about soundproofing. While he probably won’t be able to block all the sound from his room, Charles can take steps to minimize the sound that he does hear.
Average volumes of people talking, television sounds, and music playing can often be heard through walls easily. This is due to the fact that sound is a series of vibrations that move surrounding particles. The series of vibrations, or sound waves, carries the noise from the noise source across the room to our ears. Since particles are required to carry the vibrations, sound cannot travel in a vacuum. The more densely packed those particles are, the better the sound moves through since the particles don’t have to move the surrounding particles much. When you’re in an open field, though, you would notice that sound will not carry as well since the particles are more spread out. The farther sound waves have to travel from one point to another, the fainter the sound will become. When sound waves collide with a solid surface (e.g., a bedroom wall), there are a few things that can happen. The surface will reflect some of those vibrations back toward the source, it will absorb some of the sound by converting the vibrations into heat energy or it will transmit the vibrations to the other side (i.e., into the bedroom).
There are two main things to consider when soundproofing: noise transmission and noise reception. The sound coming from the trumpet is a noise transmission issue, while the desire to block the sound out is a noise reception issue. Next the source of the noise should be considered: the indoor noise vibrations your body feels are structure-borne noise, while overhearing a conversation is airborne noise. Soundproofing can be achieved by considering space, mass, and dampening. Space increases the amount of air between your ears and the source, which diffuses the noise by taking away the vibration channels. Mass, like a bedroom wall, can act as a sound sponge that soaks in the sound waves. Dampening sound requires specific materials (like insulation) that will convert structure-borne sound waves to heat energy. Dampening can be expensive.
Without having to spend money, one step Charles can take while his brother is practicing the trumpet is to create more distance between himself and his brother. For example, Charles can plan to hang out in the basement or another room in the house that’s far away from his bedroom while his brother is practicing. Or Charles could ask his brother to practice in another room that’s far away from his bedroom.
Little Lion Experiment
You cannot see sound waves in the air, but you can see their effects. This experiment will help you see the effects of sound waves. You will need: 1 large cake or cookie tin, 1 sheet of plastic wrap, 1 long rubber band, 1 baking tray, 1 wooden spoon, and some fine sand.
Steps: 1) Make a drum by stretching a piece of plastic film over a large round tin; 2) Stretch the rubber band around the tin to hold the plastic taut; 3) Sprinkle a teaspoon of sand on to the top of the plastic drumskin; and 4) Hold a baking tray above your drum, and hit it sharply with a wooden spoon.
What did you observe? What do you think caused the sand to dance up and down on the drumskin? When you struck the baking tray, the metal continued to vibrate for a fraction of a second afterward. As it vibrated, the air around is also vibrated. These little vibrations in the air, the sound waves, quickly work their way out through the air in all directions. When the sound waves hit the drumskin, the drumskin is vibrated too, which causes the sand to dance up and down on the drumskin. The sound waves that reach your ear make you hear the bang.
Average volumes of people talking, television sounds, and music playing can often be heard through walls easily. This is due to the fact that sound is a series of vibrations that move surrounding particles. The series of vibrations, or sound waves, carries the noise from the noise source across the room to our ears. Since particles are required to carry the vibrations, sound cannot travel in a vacuum. The more densely packed those particles are, the better the sound moves through since the particles don’t have to move the surrounding particles much. When you’re in an open field, though, you would notice that sound will not carry as well since the particles are more spread out. The farther sound waves have to travel from one point to another, the fainter the sound will become. When sound waves collide with a solid surface (e.g., a bedroom wall), there are a few things that can happen. The surface will reflect some of those vibrations back toward the source, it will absorb some of the sound by converting the vibrations into heat energy or it will transmit the vibrations to the other side (i.e., into the bedroom).
There are two main things to consider when soundproofing: noise transmission and noise reception. The sound coming from the trumpet is a noise transmission issue, while the desire to block the sound out is a noise reception issue. Next the source of the noise should be considered: the indoor noise vibrations your body feels are structure-borne noise, while overhearing a conversation is airborne noise. Soundproofing can be achieved by considering space, mass, and dampening. Space increases the amount of air between your ears and the source, which diffuses the noise by taking away the vibration channels. Mass, like a bedroom wall, can act as a sound sponge that soaks in the sound waves. Dampening sound requires specific materials (like insulation) that will convert structure-borne sound waves to heat energy. Dampening can be expensive.
Without having to spend money, one step Charles can take while his brother is practicing the trumpet is to create more distance between himself and his brother. For example, Charles can plan to hang out in the basement or another room in the house that’s far away from his bedroom while his brother is practicing. Or Charles could ask his brother to practice in another room that’s far away from his bedroom.
Little Lion Experiment
You cannot see sound waves in the air, but you can see their effects. This experiment will help you see the effects of sound waves. You will need: 1 large cake or cookie tin, 1 sheet of plastic wrap, 1 long rubber band, 1 baking tray, 1 wooden spoon, and some fine sand.
Steps: 1) Make a drum by stretching a piece of plastic film over a large round tin; 2) Stretch the rubber band around the tin to hold the plastic taut; 3) Sprinkle a teaspoon of sand on to the top of the plastic drumskin; and 4) Hold a baking tray above your drum, and hit it sharply with a wooden spoon.
What did you observe? What do you think caused the sand to dance up and down on the drumskin? When you struck the baking tray, the metal continued to vibrate for a fraction of a second afterward. As it vibrated, the air around is also vibrated. These little vibrations in the air, the sound waves, quickly work their way out through the air in all directions. When the sound waves hit the drumskin, the drumskin is vibrated too, which causes the sand to dance up and down on the drumskin. The sound waves that reach your ear make you hear the bang.
Thursday, January 15, 2009
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.
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.
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