A Particle Model of Metals
The objective of this lab is to learn more about the basic particle model for metals.
Review of Scientific Principles:
Metallic crystals are not perfect. Sometimes there are empty spaces, vacancies, where an atom should be. There are also small mismatches, dislocations, in the rows of atoms, and these are found in all metals.
Defects in the crystal structure of metals control many of their properties including hardness and ductility.
Time: 40 minutes
Materials and Supplies:
Plastic Petri Dish
Your team will be given a covered Petri dish containing Bb's. Keep the dish flat on the table so no Bb's spill out! Answer the Questions which correspond to a given procedure. Try to write complete idea answers; that increases understanding.
1. Describe the bonding between the atoms in a metal.
2. What type of energy do "moving" atoms possess?
3. Do the atoms in a crystal move?
4. Describe the arrangement of the Bb's. Are there any empty spaces, i.e., places where a Bb is missing?
5. Are the Bb's arranged perfectly? Would you expect atoms to be perfectly arranged?
6. Do more or less defects exist in the metal when it is heated?
Answers to Questions
1. The valence electrons of a metal atom are loosely held and considered to be shared by all the atoms in the crystal. This is called the electron sea model.
2. Kinetic energy.
3. Yes, they vibrate about an equilibrium position.
4. Student answer.
5. It is unlikely that the atoms are perfectly arranged. Some disorder is expected.
6. More defects exist at higher temperatures.