Web Scavenger Hunt

Questions with Best Answers

The answers given here were chosen by the judges to be the best answer
of those submitted by the teams for that question. Links are not listed.

1	Copper is more dense and currently, more expensive than aluminum. Why is aluminum not used in wiring in our homes? Best Answer: Corrosion of the metals in the connection, particularly the aluminum wire itself, causes increased resistance to the flow of electric current and that resistance causes overheating
2	What is the most used metal (by mass) in a standard new construction home? Best Answer: The metal that is used most in homes is steel, an alloy of iron and copper. This metal is ideal because the copper and steel combine in a crystal latice that is stronger than either of the elements apart. It is not very expensive to make, yet very supportive and thus effective. It can withstand higher temperatures, making it ideal for lasting a long time in homes.
3	What is sheetrock (be specific) and how is it produced? Best Answer: Sheetrock is another term for wallboard, drywall, gypsum or blueboard. Sheetrock is made primarily from gypsum plaster, the semi-hydrous form of calcium sulphate (CaSO4.½ H2O). The plaster is mixed with fiber (typically paper and/or fiberglass), foaming agent, various additives that increase mildew and fire resistance, and water and is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiberglass mats. When the core sets and is dried, the sandwich becomes rigid and strong enough for use as a building material.
4	What does PVC stand for and detail the process by which it is made. Best Answer: PVC stands for polyvinyl chloride. Production: first, ethylene dichloride is produced by chlorinating ethylene either by direct chorination or oxychlorination. In the first, ethylene is reacted with chlorine. In oxychlorination, ethylene is reacted with dry hydrogen chloride and oxygen at temp. less than 325 degrees Celsius. The ethylene dichloride that is produced is put under pressures between 20-30 atm. and temps between 550-650 degrees Celsius. This produces equal parts of vinyl chloride monomer [5] and hydrogen chloride. the vinyl chloride monomer is isolated. lastly, PVC is produced by the polymerization (chemical reaction linking the molecules of a simple substance together to form large molecules that have a molecular weight multiple times greater than the monomer) of the vinyl chloride monomer.
5	What happens to PVC in hot water heaters that is should not be used in this environment but can still be used in general plumbing? Best Answer: It was discovered that PVC will exhibit wall softening and glue joint failures at temperatures approaching 150degF, which explains why the ASTM standard for PVC now limits it to applications not exceeding 140degF. ) At high temperatures PVC softens, and will eventually bulge, crack, and burst, resulting in a leak.
6	What is an “R value”? Which material has the highest R value? Best Answer: An r-value is the measure of the capacity of a material, such as insulation, to impede heat flow, the higher the R-value, the greater the insulating effectiveness. 1.8-2 pound polyurethane foam has the highest R-value (7 per in.) of all readily available, cost effective insulations available in the market today.
7	Windows typically have low R values. What effects are taken by manufacturers to compensate for this? Best Answer: The r-value of glass is low, with means glass is a poor insulator. To compensate for this, two or more layers of glass are sealed together with air or gas between the two layers. This creates a highly efficient thermal unit that removes humidity from the air when the edges are later sealed and enhances thermal performance by reducing the amount of heat loss. Gas filled insulated glass also enhances sound control.
8	What is the difference between concrete, cement, and Portland cement? Best Answer: cement is a binder, a substance which sets and hardens independently, and can bind other materials together. Portland is a specific type of cement used to make concrete. It is a combination of calcium, aluminum, silicon and iron oxides in specific combinations, made from a raw material mix of limestone, chalk, and clay, or their natural blend, lime marl. Concrete is a construction material that consists of Portland cement, construction aggregate (generally gravel and sand) and water.
9	Where is paper used in the construction of homes? Best Answer: Papercrete is essentially a type of industrial strength paper maché made with paper and cardboard, sand and portland cement. The concept is quite simple -- you build a mixer (essentially a huge kitchen blender), mix the dry ingredients with water to form a slurry, cast the slurry into blocks or panels, and let it dry. When it hardens up, papercrete is lightweight (it's 80 percent air), an excellent insulator (R 2.8 per inch), holds its shape even when wet, and is remarkably strong (compressive strength of 260 psi). And, since it contains paper fibers, it has considerable tensile strength as well as compressive strength. Papercrete is a remarkable building material, and is remarkably inexpensive, since all the ingredients (except for the cement) are free or nearly free. Used in places where adobe is very popular like New Mexico.
10	“People who live in glass houses shouldn’t.” Where is glass (any type) used in houses? Best Answer: Glass most known for its use in windows but also is used in fiber form in insulation common in roofs and walls as well as formed glass that can be used as light-weight closed cell circulation.
11	Explain why homes in cold climates have pitched roofs but large attics (is it because we tend to be packrats?) while homes in warmer climates may still have pitched roofs, but have high ceilings and no attic. Best Answer: Ice dams sometimes occur on sloping roofs in climates with freezing temperatures. When the temperature in your attic is above freezing, it causes snow on the roof to melt and run down the sloping roof. When the snowmelt runs down the roof and hits the colder eaves, it refreezes. If this cycle repeats over several days, the freezing snowmelt builds up and forms a dam of ice, behind which water ponds. The ponding water can back up under the roof covering and leak into the attic or along exterior walls. Condensation of water vapor on cold surfaces in attics can cause attic wood products to rot, which can lead to costly repairs. Condensation typically occurs when warm, moist air migrates into the attic from living spaces below. Research indicates unusually high humidity levels in the home's living spaces is strongly associated with attic condensation problems. Perhaps the most significant finding from the study, performed by the Florida Solar Energy Center, was that the presence of highly insulated ceilings in homes with attic ducts appeared to decrease savings.Much of the savings were driven by thermal interactions between the duct system and the attic space.
12	Compare and contrast two different types of roofing materials. Best Answer: Asphalt Shingles The least expensive type of shingle, asphalt shingles are also the most common. These shingles are thin, made from fiberglass and asphalt, and can last from 15 to 20 years. Laminated Fiberglass Shingles These shingles are made like asphalt shingles and contain the same materials. However, they’re thicker and give a more textured look to your roof. They cost at least twice as much as the common asphalt shingle, but can last longer, up to 30 years.
13	Many synthetic fibers are used in carpeting and flooring. Describe three man-made compounds used in flooring. Best Answer: Nylon is a synthetic fiber from which almost 75% of carpet today is made. It is the leader in: appearance retention, fade and heat resistance, soil and stain resistance, and color and styling. Polyester is a common synthetic material well accepted for its bulkiness, color clarity, and good stain and fade resistance, while not as resilient as nylon, polyester fiber carpet constructed with today’s new technologies can be a good performer. Polypropylene is another common synthetic material used in carpet manufacturing; sometimes it is referred to as olefin. Today it represents more than thirty-five percent of the total fibers used in the carpet industry. However polypropylene is not as resilient or resistant to abrasion as nylon, but it is naturally stain and fade resistant. It is most often used in loop pile carpet constructions.
14	Paints come in two general categories, oil and latex. Describe the similarities and differences between oil and latex paint. Best Answer: Paints are made of three main parts: pigment for color, a binder/resin to make the paint stick and form an even layer, and a carrier or solvent. The carrier or solvent keeps the paint in liquid form while in the can and evaportates when exposed to the air, to form a solid material. This compositon connects all paints, but the type of carrier or solvent differentiates between the paints. Latex paints are water-based, and therefore dry faster (more volatile than petroleum). Latex paint also easily cleans up with water, because likes dissolve likes (water is polar and since latex paint is water-based, latex paint is polar). Latex paints spread thinner because they have a lower viscosity and less intermolecular forces. Oil paints, or alkyd paints are petroleum based. They are water resistent because they are nonpolar, and therefore have high scrubbability and are very durable. Oil paints contain more compounds with health effects, such as formaldehyde, toluene, xylene and benzene. This makes this type of paint harmful to the environment.
15	Paint consists of a polymer and a plasticizer. Describe the purpose of these components and how they work together. Best Answer: Polymers are the main support to the paint, due to the long chains of atoms, and form a very strong result by these large chains combining. Plasticizers dissolve in the paint and make the substance stick to whatever is being painted. Polymers are generally fairly rigid, so the addition of the plasticizers makes the paint more flexible, by slightly weakening the intermolecular forces, so that the paint may cover odd-shaped or curved surfaces.
16	Stain, varnish and paint are means to finish wood. Compare and contrast these substances. Best Answer: Stain is composed of the same three primary ingredients as paint (pigment, solvent, and binder) but is predominantly pigment (or dye) and solvent with little binder. Stains are differentiated from varnishes in that the latter has no added color or pigment and is designed to form a surface film. Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents. Paint is the general term for a family of products used to protect and add color to an object or surface by covering it with a pigmented coating.
17	Give at least three different compounds which give paints different colors (white included). Best Answer: Titanium dioxide gives white paint its color. Chemically pure cadmium-sulfide pigments are used to make yellow colors. Cobalt blue paints are created using cobalt. Copper Chromite Black made from the calcination of copper oxide and chromium oxide
18	Pressure treated wood used to be treated with arsenic. Describe how arsenic helped retard the weathering process of wood and what is currently used to prevent weathering. Best Answer: Chromated copper arsenate or CCA, is a chemical preservative that protects wood from rotting due to insects and microbial agents. CCA contains arsenic, chromium and copper. CCA has been used to pressure treat lumber used for decks, playgrounds (playsets) and other outdoor uses since the 1930’s. Since the 1970’s, the majority of the wood used in residential settings was CCA-treated wood. Arsenic is lodged into the wood under high pressure and acts as a coat protector against insects and water which keeps the wood from rotting. There are a number of non-arsenic containing preservatives that have been registered by EPA to pressure-treat wood for consumer applications. ACQ (ammonium copper quaternary) and copper boron azole (CBA) are common ones. Some wood treated with these preservatives is already available at retail outlets such as home improvement stores. In addition, playground equipment made of other non-arsenic containing components is also available (e.g. woods such as cedar and redwood and non-wood alternatives such as metals and plastics).
19	Methane (CH4) is an odorless, colorless gas. Natural gas is stinky. What component is detected by humans and explain in detail how our noses detect it. Best Answer: A trace amount of smelly organic sulfur compounds (tertiary-butyl mercaptan, (CH3)3CSH and dimethyl sulfide, CH3–S–CH3) is added to give commercial natural gas a detectable odor. This is done to make gas leaks readily detectible.
20	Mold is an increasing problem in homes. Describe the type of mold that is a concern and how this problem can be combated. Best Answer: Although all types of molds in homes are a concern and potentially harmful, the one type that has been getting the most attention is Stachybotrys chartarum, or "black" mold. This mold is wet, slimy, and greenish-black, but is not commonly found in homes. This can cauese a variety of problems, the most serious being a respiratory illnesses such as idiopathic pulmonary hemorrhage. There are two species of Aspergillus, flavus and parasiticus, which usually come with "black" mold and produce potent carcinogens. We can prevent this mold from growing by making sure that houses are well-ventilated, such as by installing ceiling fans. If a water leak or flooding does occur, it should be cleaned up immediately, and carpeting should be avoided in very humid rooms. We should also use mold-cleaning supplies in bathrooms and use non-cellulose and low nitrogen replacement materials as much as possible. We should also try to control mositure build-up by warming up cool surfaces, such as with installation, and by using storm or double-paned windows. Finally, add mold inhibitors or fungicides to paint. These precautions will hopefully prevent the mold from forming, but if it is already occuring, it is best to clean it up as soon as possible.
21	Utility costs are rising. Describe one alternate way of heating a home which does not involve the burning of any fuel (oil, gas, natural gas, propane, wood, etc.) and would result in the lowering one’s utility bill (thus, you cannot simply switch to an electric heater). Best Answer: One way to reduce one's utility bills is to use solar power. Solar power uses the sun's energy and transfers it into electricity. Solar panels are made of photovoltaic (PV) cells. These cells are made of semiconductors, usually silicon. When the light hits the cell, some of the energy is absorbed, and thus transfered into the semiconductor. This energy hits some electrons loose, allowing them to flow freely. PV cells have one or more electric feilds that direct the electrons which are knocked loose. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, the electricity is able to be used by the owner.
22	Batteries in smoke detectors should be changed at least twice a year (daylight savings time ends on Sunday, have you changed your batteries?). How do smoke detectors detect smoke? Best Answer: Ionization smoke detectors (most common) use an ionization chamber and a source of ionizing radiation to detect smoke. Inside an ionization detector is a small amount of americium-241. An ionization chamber is very simple. It consists of two plates with a voltage across them, along with a radioactive source of ionizing radiation. The alpha particles generated by the americium ionizes the oxygen and nitrogen atoms of the air in the chamber. The electronics in the smoke detector sense the small amount of electrical current that these electrons and ions moving toward the plates represent. When smoke enters the ionization chamber, it disrupts this current -- the smoke particles attach to the ions and neutralize them. The smoke detector senses the drop in current between the plates and sets off the horn.
23	Some homes have wells and the water may be “hard”. In order to fix this homes have water softeners to make the water “soft”. What is hard water versus soft water and how does a water softener work? Best Answer: Water is hard if it contains a lot of calcium or magnesious dissolved in it. This can cause a scale build-up inside the pipes, which can eventually clog the pipes. The magnesium and calcium also reacts with soap to form a sticky scum, and reduces soap's ability to lather. In order to remove these affects, the magnesium and calcium ions are switched with sodium ions. Sodium ions do not cause a build-up (because it is soluble with most anions) and does not reduce soap's ability to lather. To switch the ions, all the water used in the house is put through a bed of small plastic beads or through a chemical matrix called zeolite. The beads or zeolite are covered with sodium ions so that the ions swap places as the water runs through. Eventually, the beads or zeolite contain nothing but calcium and magnesium ions and no sodium ions, and at this point they stop softening the water. It is then time to regenerate the beads or zeolite; you do this by adding salt, or sodium chloride. A very strong solution is made that is run through the beads or zeolite. This flushes out the calcium and magnesium while restoring the sodium ions.
24	Why do halogen light bulbs look very white (or almost blue) while standard tungsten filament light bulbs look softer (almost yellow). Best Answer: The mixture of Xenon and Halogen gas in the high color temperature environment produces a very bright white light beam with a blue background (Xenon Blue) similar to the HID lighting. The ultimate result is a bright white light beam that is noticeably sharper and brighter than other light sources. Also, standard tungsten light bulbs have a colour temperature of 3200 K and are very yellow. Your eyes adjust to this light, making it appear whiter and more like daylight. At twilight or at night, anything with a higher colour temperature than tungsten lights, such as a television, appears distinctly blue.
25	Why do you hear a “pop” when a light bulb breaks? Why is this included in the production of tungsten filament light bulbs? Best Answer: A partial vacuum is created within the light bulb. The pop is air going into the semi-vacuum inside the bulb. The vacuum is created so the materials inside the bulb do not combust.