ACS is committed to helping combat the global COVID-19 pandemic with initiatives and free resources. Learn More

Chemistry Outcomes Review: Chapter 1

Water: A Natural Wonder

The next time you "plunge your hands in water" or watch ice cubes floating in a glass of water, you won't "wonder what you've missed," because you can interpret the observable properties of water ― and some other compounds ― in terms of an atomic-molecular model and the interactions of the molecules with one another.

In your mind's eye, you'll see the bent, polar water molecules hydrogen bonding to their neighbors with the molecules held together as a liquid or as a solid. And you can relate the properties of different compounds to one another by using our molecular models of matter and comparisons based on counting molecules or moles. You are prepared now to go on, in Chapter 2, to learn how the structure of water molecules affects the interactions of water with other substances and to deepen your understanding of the mole concept.

Before going on, check your understanding of the ideas in this chapter by reviewing these expected outcomes of your study.

You should be able to:

  • Describe solids, liquids, and gases in terms of their macroscopic properties and write or draw molecular-level descriptions that explain these properties [Section 1.1].
  • Make drawings that show how the electrical nature of matter explains the results of electrostatic experiments [Section 1.2].
  • Use the nuclear atomic model, the shell model for electrons, and the periodic table to determine the charge on the atomic core and the number of valence electrons in an atom [Section 1.2].
  • Use the periodic table and the atomic shell model to predict trends in atomic size and electronegativities [Sections 1.2 and 1.6].
  • Describe the relationships among different molecular models and the information that each of them provides [Sections 1.3, 1.4, 1.5, and 1.6].
  • Write Lewis structures for molecules whose molecular formulas contain only first and second period elements [Section 1.4].
  • Use drawings, physical models, and words to describe the geometry of the valence electrons and nuclei for molecules whose molecular formulas contain only first and second period elements [Section 1.5].
  • Predict the direction and relative magnitude of bond dipoles and the direction of the resultant molecular dipole for simple molecular structures [Section 1.6].
  • Use drawings, physical models, and words to describe the origin of intermolecular interactions due to London dispersion forces, dipolar attractions, and hydrogen bonding [Section 1.7].
  • Use intermolecular attractions to predict and/or explain trends in boiling points and energies of vaporization for a series of compounds whose molecular structures you know or can determine [Sections 1.7 and 1.11].
  • Use drawings, physical models, and words to describe how the structure of the water molecule is responsible for the densities of solid and liquid water, the temperature dependence of the density of liquid water, and the consequences for life on Earth [Section 1.8].
  • Describe some of the places where hydrogen bonding occurs in biomolecules and explain how hydrogen bonding is important for the functions of these molecules [Section 1.9].
  • Describe and use energy diagrams to illustrate the direction of energy transfer from one substance to another when phase changes occur [Section 1.10].
  • Use the relationship among energy change, temperature change, mass, and specific heat to make quantitative comparisons between two substances that gain or lose thermal energy [Sections 1.10, 1.11, and 1.12].
  • Use the molar mass of a compound, determined from the relative atomic masses of its constituent atoms, to calculate the number of moles in a given mass of the compound [Section 1.11].
  • Use drawings, physical models, and words to describe the molecular basis for the differences in specific heats among different compounds [Section 1.12].