April/May 2015 Teacher's Guide for Smartphones, Smart Chemistry Table of Contents

Answers to Student Questions

1. 
   Why will your smartphone be obsolete in a year or two? According to the author, your smartphone will be practically obsolete “because the smartphone just keeps getting smarter.”
   
2. 
   How many nonradioactive elements can be found in smartphones? More than 70 stable elements can be found in smartphones today.
   
3. 
   Which group of metals plays a pivotal role in the smartphone? The rare-earth metals is the group that is crucial to the manufacture of smartphones.
   
4. 
   Why are scandium and yttrium included in the rare-earth metals, even though they’re not part of the lanthanide series of elements? Scandium and yttrium are included in the rare-earth metals, even though they are not located in the lanthanide series because their chemical properties are similar to those of the lanthanides.
   
5. 
   Which of the rare-earth elements is not included in smartphones? Why? The rare-earth metal not included in smartphones is promethium, because it is radioactive.
   
6. 
   What other electronic devices use rare-earth metals? Other electronic devices using rare-earth elements include televisions, computers, lasers, missiles, camera lenses, fluorescent light bulbs and catalytic convertors.
   
7. 
   What major challenge faces the cell-phone industry, according to the author? According to the author, finding suitable replacement elements for many of the rare-earth elements is one of the biggest challenges facing the smartphone industry.
   
8. 
   What are the characteristic properties of a glass-ceramic? A glass-ceramic is
   
   1. 
      A much tougher and stronger material than either of the two materials by themselves.
      
   2. 
      Typically, at least 50% crystalline, sometimes going as high as 95% crystalline.
      
   3. 
      Heat-resistant
      
9. 
   List the materials of which Gorilla Glass is composed. Gorilla Glass is made of aluminosilicate glass, which is composed of
   

1. 
   Alumina oxide, or alumina,
   
2. 
   Silicon dioxide, or silica, and
   
3. 
   Sodium ions
   

10. 
    What is the effect of adding potassium ions in the final step to give Gorilla Glass its tremendous strength? The addition of potassium ions strengthens the glass. Potassium ions displace sodium ions on the surface of the glass. Because the potassium ions are larger than sodium ions, the surface ions push on each other and on the rest of the glass, compressing it and making it very strong.
    
11. 
    How does a resistive touchscreen work? A resistive touchscreen is made of two thin layers of conductive glass. When you press on the top layer, it indents, causing the two layers to touch. This completes the circuit and changes the electrical current at the point of contact. The software recognizes this change at the specific coordinates and executes the function that corresponds to that location.
    
12. 
    How does a capacitive touchscreen work? Since glass itself does not conduct electricity, a capacitive touchscreen contains a conducting surface layer, usually of indium tin oxide, that stores electricity on the surface. Because your skin is conductive, when you touch the screen, some of that electricity flows into your finger. The screen registers the voltage drop, and the software recognizes this change in voltage at that specific location and executes the corresponding function.