Exploring materials

Polymers and composites Carbon chains- straight chains, branched chains, rings. Most polymers and composites consists of these three carbon molecules.

Carbon compounds form polymers Polymer- a large complex molecule built from smaller molecules joined together. Monomers- small carbon base molecules from which polymers are built. Polymers form when chemical bonds link large numbers of monomers in a repeating pattern.

Natural polymers Plant polymers- polymers made from plants, utilizing cellulose. Cellulose- a flexible but strong natural polymer that gives shape to plant cells. Animal polymers- polymers made from animal proteins, which are built from amino acids( monomers).

Synthetic polymers Plastics- synthetic polymers that can be molded or shaped. Made from coal or oil. Composites- two or more substances as a new material with different properties. Chemists can make a new material that works better than either one alone.

Natural composites Wood- a natural composites made of long fibers of cellulose, held together by another plant polymer called lignin. Synthetic composites- combinations of synthetic polymers that combine the desired properties.

Metal and alloys Properties of metal- hard and usually shiny, solids at room temperature, and conduct electricity. Alloys- a substance made from two or more elements that has properties of metal. Combining these elements gives alloys the desired properties from both elements. Alloys are used much more than pure metals because they are generally stronger, and less likely to react with air or water.

Ceramics Ceramics- hard, crystalline solids made by heating clay and other minerals to high temperatures. Properties of ceramics- resists moisture, do not conduct electricity, can withstand temperatures higher than molten metals. Used for insulators, sewer pipes, electric equipment, and light fixtures.

Glass Clear solid material with no crystal structures. Made by heating sand, creating a hot liquid. Different material may be added to make it useful for particular purposes. Optical fiber- thread like piece of glass that can be used for transmitting light.

Radioactive elements Nuclear reactions- reactions involving the particles in the nucleus of an atom. Isotopes- atoms with the same number of protons but different number of neutrons. Mass number- the sum of the protons and neutrons in the nucleus of an atom. Radioactive decay- the atomic nuclei of unstable isotopes release fast moving particles and energy.

Particles of radioactive decay Alpha decay- alpha particles consisting of two protons and two neutrons being released by the unstable nucleus. Can be stopped by a sheet of paper or aluminum. Beta decay- a beta particle consisting of and electron given off by a nucleus during radioactive decay. can be stopped by aluminum, but can be passed into the human body and damage its cells. gamma decay- gamma radiation is high energy waves. The most penetrating type of radiation. You’ll need either lead, or a concrete wall. It can pass through the human body causing server damage to cells.

Half life Half life is the length of time needed for half the mass of a sample to decay. Half life is different for each type of isotope. Useful in determining the age of rocks and fossils. This process is called radioactive dating.

Using Radioactive Isotopes Tracers – radioactive isotopes that can be followed through the steps of a chemical reaction or industrial process. Radiation therapy – radioactive elements are used to destroy unhealthy cells. (Cancer) Nuclear power – electricity created by nuclear reaction heating water and running through a steam turbin.