day 4 week 5

2SCS: 


18. a. Reusing is using an item again after it has been initially used. Recycling is processing reused materials into new products. 
      b. Reusing grocery bags, recycling water bottles 


19. a. water, oxygen, timber, sun 
       b. copper, oil, gas, coal


20. a. reusing 
        b. recycling 
        c. reusing


21. The life cycle of a light bulb and a newspaper are similar because in both processes, raw materials are obtained and then refined into the desired material. 


2SDS: 


1. An allotrope is a different form of an element that has distinctly different physical or chemical properties. 


2. Oxygen and nitrogen form allotropes. 


3. a. The properties of a diamond, a chunk of coal, and pencil lead are different because: a diamond has the highest melting point among all of the other elements and it's cost depends on it's quality and esthetic characteristics, a chunk of coal is not very expensive, and pencil lead is made of graphite. 
     b. Their properties are different because the atoms are bonded together differently
     c. The cut, appearance, and quality of these materials all effect and differentiate their costs


4. Engineered materials differ from natural materials because they are made for specific purposes and can be made up of natural materials, however, natural materials are untouched and unaltered through manmade changes.  


5. Two advantages of using engineered ceramics in high-temperature applications are that the efficiency is increased, therefore fuel use is reduced. A disadvantage is that ceramics can fracture if exposed to sudden temperature changes. 


6. Polyethylene can be tailored to display properties for specific applications. Optical fibers are also being developed to replace conventional copper.