Plastic Definition and Examples in Chemistry

Plastic Definition and Examples in Chemistry Have you ever wondered about the chemical composition of plastic or how it is made? Heres a look at what plastic is and how it is formed. Plastic Definition and Composition Plastic is any synthetic or semisynthetic organic polymer. In other words, while other elements might be present, plastics always include carbon and hydrogen. While plastics may be made from just about any organic polymer, most industrial plastic is made from petrochemicals. Thermoplastics and thermosetting polymers are the two types of plastic. The name plastic refers to the property of plasticity, the ability to deform without breaking. The polymer used to make a plastic is almost always mixed with additives, including colorants, plasticizers, stabilizers, fillers, and reinforcements. These additives affect the chemical composition, chemical properties, and mechanical properties of a plastic, along with its cost. Thermosets and Thermoplastics Thermosetting polymers, also known as thermosets, solidify into a permanent shape. They are amorphous and are considered to have infinite molecular weight. Thermoplastics, on the other hand, can be heated and remolded over and over again. Some thermoplastics are amorphous, while some have a partially crystalline structure. Thermoplastics typically have a molecular weight between 20,000 to 500,000 amu. Examples of Plastics Plastics are often referred to by the acronyms for their chemical formulas: Polyethylene terephthalate: PET or PETEHigh-density polyethylene: HDPEPolyvinyl chloride: PVCPolypropylene: PPPolystyrene: PSLow-density polyethylene: LDPE Properties of Plastics The properties of plastics depend on the chemical composition of the subunits, the arrangement of these subunits, and the processing method. All plastics are polymers, but not all polymers are plastic. Plastic polymers consist of chains of linked subunits, called monomers. If identical monomers are joined, it forms a homopolymer. Difference monomers link to form copolymers. Homopolymers and copolymers may be either straight chains or branched chains. Here are some other properties: Plastics are usually solids. They may be amorphous solids, crystalline solids, or semicrystalline solids (crystallites).Plastics are usually poor conductors of heat and electricity. Most are insulators with a high dielectric strength.Glassy polymers tend to be stiff (e.g., polystyrene). However, thin sheets of these polymers can be used as films (e.g., polyethylene).Nearly all plastics display elongation when they are stressed that is not recovered after the stress is removed. This is called creep.  Plastics tend to be durable, with a slow rate of degradation. Interesting Plastic Facts Additional facts about plastics: The first completely synthetic plastic was Bakelite, made in 1907 by Leo Baekeland. Baekeland also coined the word plastics.The word plastic comes from the Greek word plastikos, which means that it can be shaped or molded.Approximately a third of the plastic that is produced is used to make packaging. Another third is used for siding and piping.Pure plastics are generally insoluble in water and nontoxic. However, many of the additives in plastics are toxic and may leach into the environment. Examples of toxic additives include phthalates. Nontoxic polymers may also degrade into chemicals when they are heated.

Fun French Number Practice for the Classroom

Fun French Number Practice for the Classroom Do you find teaching numbers boring, figuring that once youve taught your students to count in French, theres not much else you can do? If so, I have good news for you (and your students). Here are some great ideas for practicing numbers, including several games. Simple French Number Practice Ideas Use flash cards with the digit written on one side and the French spelling of the number on the other. Ask students to count by twos, fives, tens, etc.Count different objects in the classroom: number of desks, chairs, windows, doors, students, etc.Practice numbers with math operations: adding, subtracting, etc.Print out some paper money or use pennies and practice numbers by counting money.Talk about the time and date.Depending on the age of your students and your concerns about privacy, you could ask students about various personal details in French: birthdayagenumber and ages of brothers, sisters, cousin(e)sphone numberaddress You or your students can bring in pictures of food, clothing, dishes, office supplies, etc. and then discuss how much each item might cost - Ça coà »te 152,25 euros, for example. Good for combining number practice with other vocabulary words.One teacher found that students forgot to use the word ans when describing someones age, so now at the beginning of class, she writes the names of one or two celebrities or notable French people on the chalkboard and students guess his/her age. You can find birthdays in Today in Francophone history. Fun French Numbers Practice, Games and Activities British Bulldog / Dog and Bone A game for outdoors or a gymnasium: Divide the class in half, and have each side stand in a long line facing the other half, with a large gap for running between the two teams. Give each member a number: each team should have the same set of numbers but in a different order so that the students with the same number are not facing each other. An article, such as a scarf, skittle, or baton, is placed in the space between the two teams. Then the teacher calls a number and the student from each team with that number races to retrieve the article. Whoever gets it earns a point for his/her team. Number Toss Have the students stand in a circle and throw a nerf ball to another student (not adjacent). Upon catching the ball the student must say the next number. If s/he doesnt know what number youre on, says the wrong number, or pronounces it incorrectly, s/he is out of the game. Phone Numbers Have students write their actual phone numbers on a small piece of paper with no names. You can play too, by writing a phone number that you know well (such as the schools if you dont want to use your own). Collect the slips of paper and pass them back out randomly, making sure that no one has his/her own number. Everyone stands up. Start the game by reading the number on the paper you have. The person whose number it is sits down and reads the number s/he has, and so on until everyone is seated. Works well for listening, but they have to be able to say the numbers accurately enough for their classmates to understand them. I do this once theyve learned 0 to 9. Le Prix est Juste / The Price Is Right Teacher thinks of a number and gives students a range to guess from. Students respond and if incorrect, the teacher responds with plus or moins. When a student finally guesses the correct answer, s/he can be rewarded with a sticker, piece of candy, or a point for the team. Then the teacher thinks of a new number and gives a range and students begin guessing again. TPR with Numbers Write numbers on large cards, then call out instructions to the students: Mettez trente sur la table, Mettez sept sous la chaise (if they know prepositions and classroom vocabulary for example). You can mix it up with other vocabulary to catch them off guard and keep their attention: Donnez vingt Paul, Mettez la prof sur huit, Tournez vingt, Marchez vite avec onze. Or you can put the cards on the chalk tray and practice with avant, aprà ¨s, and cà ´tà © de: Mettez trente avant seize, Mettez zà ©ro aprà ¨s dix, etc. You might want to start with just five or so numbers at first; when they get good at those, add a couple more and so on. Zut Go around the room and count. Each time there is a 7 - a number with 7 in it (like 17, 27) or a multiple of 7 (14, 21) - the student must say zut instead of the number. They are knocked out of the game if they mispronounce the number, say the wrong number, or say the number when they should say zut. So the game should sound like this: 1, 2, 3, 4, 5, 6, zut, 8, 9, 10, 11, 12, 13, zut, 15, 16, zut, 18, 19, 20.... You can change the zut number periodically to keep them on their toes.