Chapter 1: ATOMS

08-Jun-2012

Knowledge Statements

  1. Models (mental and physical) are used to represent many chemical entities. We use different models for different purposes, often to describe the same phenomena. 
  2. Theories (such as atomic theory) explain large numbers of observations in a coherent, predictive form. While there are alternative models, there are no such things as "alternative theories" in science. Theories may change over time as new evidence is found
  3. Matter is made of atoms that are the smallest distinguishable part of an element. Atoms are composed of a relatively massive, small, and positively charged nucleus and a “cloud” of negatively charged, relatively light electrons.
  4. All (neutral) atoms and molecules attract each other via London dispersion forces. Attractions lower the potential energy of a system. The more stable the system, the lower its potential energy
  5. The stability of a system is a function of its potential energy and energy that can be transferred to it from its surroundings (via collisions or the absorption of light).
  6. In a closed system (and the universe as a whole) energy is conserved. If the potential energy of a system decreases it is transformed into kinetic energy, which may be transferred to the surroundings via collisions with other atoms or molecules.

Performance expectations (after studying the chapter and working through the materials, you should be able to:)

  • Provide a coherent rationale for how you would distinguish a fact, from a law, from a model, from a hypothesis, from a theory; provide an example of each. (1,2)
  • Construct a scientific question and explain what features make it scientific (as opposed to non-scientific).
  • Describe how evidence from various experiments was used to argue for the existence of: (3)
    atoms
    electron, protons, and neutrons
    a small, massive, and positively charged nucleus
  • Using the current model of the atom presented in the chapter, explain why matter is conserved in chemical reactions, and why compounds always have the same chemical composition. (2)
  • Make estimations / comparisons about the relative sizes of atoms, simple molecules, cells and macroscopic materials. (3)
  • Construct representations that can be used to explain the changes in potential and kinetic energy as a function of internuclear distance between two atoms of a noble gas. Explain why this function differs between the different noble gases.(4-6)
  • Using the conservation of energy principle, explain the changes in potential, kinetic and total energy, as two atoms approach each other.
  • Predict the effect of introducing more atoms into the system. (4-6)
    Construct representations to show how energy is transferred from molecule to molecule in a gas, when the temperature changes.
  • Predict or rank the relative strength of London dispersion forces between atoms and molecules of different sizes, and relate these to relative melting or boiling points. (4-6)
  • Distinguish (but not necessarily explain) intermolecular attraction from covalent bonding.(4-6)
08-Jun-2012
→ chapter 2