Science+Fair+Notes+OE

My Science Fair topic is on " What type of plastic wrap best prevents evaporation ? "

Hypothesis: I think HannaFarm brand of plastic wrap because I think it is the best to prevent evaporation the best.

Notes:

[] I know because it is made by professionals that know what they are doing

__Source 1__

e·vap·o·rate (-vp-rt) //v.// **e·vap·o·rat·ed**, **e·vap·o·rat·ing**, **e·vap·o·rates** //v.////tr.// //v.////intr.// Source 2 []
 * 1.****a.** To convert or change into a vapor.
 * b.** To draw off in the form of vapor.
 * 2.** To draw moisture from, as by heating, leaving only the dry solid portion.
 * 3.** To deposit (a metal) on a substrate by vacuum sublimation.
 * 1.****a.** To change into vapor.
 * b.** To pass off in or as vapor.
 * 2.** To produce vapor.
 * 3.** To disappear; vanish: Our fears at last evaporated. See Synonyms at [|disappear].


 * I know this is a good because professionals put the information on this website

The **water cycle**, also known as the **hydrologic cycle** or the **H2O cycle**, describes the continuous movement of water on, above and below the surface of the [|Earth]. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go, in and out of the [|atmosphere]. The water moves from one reservoir to another, such as from river to [|ocean], or from the ocean to the atmosphere, by the physical processes of [|evaporation] , [|condensation] , [|precipitation] , [|infiltration] , [|runoff] , and subsurface flow. In so doing, the water goes through different phases: liquid, solid ( [|ice] ), and gas ( [|vapor] ). The water cycle involves the exchange of energy, which leads to [|temperature] changes. For instance, when water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment. These heat exchanges influence [|climate]. By transferring water from one reservoir to another, the water cycle purifies water, replenishes the land with freshwater, and transports minerals to different parts of the globe. It is also involved in reshaping the geological features of the Earth, through such processes as [|erosion] and [|sedimentation]. Finally, the water cycle figures significantly in the maintenance of life and ecosystems.

Source 3 []
 * I know this is a good because professionals put the information on this website

**Plastic wrap**, **cling film** (UK), **cling wrap** or **food wrap**, is a thin [|plastic film] typically used for sealing [|food] items in containers to keep them fresh over a longer period of time. Plastic wrap, typically sold on rolls in boxes with a cutting edge, clings to many smooth surfaces and can thus remain tight over the opening of a container without [|adhesive] or other devices. Common plastic wrap is roughly 0.5 [|mils], or 12.5 [|µm] , thick. [|[1]][|[2]] In Australia and New Zealand the [|genericized trademark] **glad wrap** is commonly used, while **Saran wrap** has become genericized in [|North America].

Plastic wrap was first created from polyvinyl chloride ( [|PVC] ), which remains the most common material. Non-PVC alternatives are now being sold due to concerns about the transfer of [|plasticizers] from PVC into food, although PVC is still the most common. For household use, low density polyethylene ( [|LDPE] ) is gaining market share as it is purportedly safer.

A number of governments are concerned about the environmental effect of PVC, as the material is said to be toxic and harder to recycle. Nevertheless, PVC is still used as its stretching properties offer excellent food catering presentation on the shelf, and it clings well to more kinds of surfaces. Even so, some countries are starting to ban the use of PVC in toys for infants and food contact applications.

The original [|Saran] Wrap is made of [|polyvinylidene chloride] (PVdC). In July 2004 the name Saran Original was changed to Saran Premium and the formulation was changed to [|LDPE]. SC Johnson claimed that this change was a result of an initiative to look for more sustainable and environmentally acceptable plastic. The film in Saran Premium Wrap does not contain chlorine. However, [|LDPE] does not possess the same barrier qualities to oxygen, aroma, and flavor molecules that vinylidene chloride copolymers do, making the new formulation a lower quality plastic wrap, as it is not as useful in protecting from spoilage or flavour loss.[// [|citation needed] //] This is because PVdC has a significantly lower water vapor transmission rate (WVTR) than LDPE. [|[4]]

The PVC-based films contain [|plasticizers], most often [|bis(2-ethylhexyl) adipate] (DEHA), but [|phthalates] (most often [|dibutyl phthalate] (DBP) and [|bis(2-ethylhexyl) phthalate] (DEHP)), in spite of being prohibited in most countries, also cause concern. The plasticizers were found to migrate to some foods, for example [|cheeses] or fatty fish and meat. In the UK, polymerized plasticizers replaced DEHP in this application, largely eliminating the problem. [|[5]]

A common alternative to PVC is [|low density polyethylene] (LDPE), which is less adhesive than PVC, but does not contain traces of these potentially toxic additives. However, newer production processes are closing the adhesive gap between PVC and LDPE. [|Linear low density polyethylene] (LLDPE) is sometimes added to the material, as it increases the adhesive qualities and the [|tensile strength] of the film. [|[6]] Brands like Saran Premium Wrap, Glad Cling Wrap and Handi-Wrap are LDPE-based.

Glad Press'n Seal has its surface covered by shaped dimples, which hold the adhesive away from the surface. While being handled, the wrap is unsticky, but when pressure is applied the dimples are flattened and the adhesive pushed against the contacting surface, sticking them together. [|[7]] The adhesive used is a special edible type similar to chewing gum. [|[8]]

PVdC has better barrier properties than the more-permeable LDPE, making the foods wrapped in it less subject to [|freezer burn] .[// [|citation needed] //] However, LDPE is substantially cheaper and easier to make.

Natural polymers of LDPE and PVdC are insufficiently adhesive on their own, and they do not adhere to themselves. To achieve the desired adhesiveness, certain polymers with lower molecular weight have to be added; the most common two are [|polyisobutene] (PIB), and [|poly[ethylene-vinylacetate]] (EVA) copolymer. Their chains readily interact with each other and their lower molecular weight makes them more mobile within the host polymer matrix. [|[9] Source 4 Science textbook = **Work Cited** =
 * The water cycle is the cycle of water for evaporation of the water cycle.

Moyer, Richard. //McGraw-Hill Science //. New York: McGraw-Hill School Division, 2000. Print.


 * I Know this is a good book because middle school uses it.

Water Cycle." //Wikipedia//. Wikimedia Foundation, 18 Sept. 2013. Web. 26 Sept. 2013. .
 * I know this is a good because professionals put the information on this website

" What is Evaporation " Web. 26 Sept. 2013.<[]>
 * I know because it is made by professionals that know what they are doing

" What is Plastic Wrap " Web.< [] >


 * I know this is a good because professionals put the information on this website