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.