Unit 5: States of Matter
In this unit, we look at how matter behaves. We will begin with gases because we can describe their behaviors and properties in straightforward equations. We will also study the phase diagram, which predicts the state (solid, liquid or gas) of any group of molecules at any given temperature or pressure.
Completing this unit should take you approximately 15 hours.
Upon successful completion of this unit, you will be able to:
- use kinetic-molecular theory to explain the relationships between gas volume, temperature, number of moles, and pressure;
- perform dimensional analysis conversions for gas law calculations;
- state the ideal gas law;
- describe the motion of particles in liquids and the properties of liquids;
- discuss the process by which liquids can change into a solid or a gas;
- define the characteristics of bonding in ionic compounds;
- interpret phase diagrams; and
- describe and explain the processes of boiling, evaporation, freezing, melting, and sublimation.
5.1: Gases and Gas Laws
Read this page. Understanding how pressure, temperature, and volume of a gas differ from those of forces that exist within solids and liquids will be fundamental for understanding the upcoming subunits of this course.
Watch these lectures, which introduce ideal gases.
Read this page. Ideal gas laws are laws that apply to gases that behave "ideally," when molecules take up no volume and have no attractive forces between one another. In the real world, however, no gas behaves ideally. However, gases are closest to being ideal when they are high-temperature and low-pressure.
Watch this lecture, which discusses partial pressure. A key concept here is that a mixture has a total pressure that is the sum of its component, or partial, pressures.
Read this page, which covers molar properties of gases and partial pressures. After reading this section, you should understand what happens to scuba divers who suffer from nitrogen narcosis, or "the bends."
Read this page. Kinetic molecular theory (KMT) explains the properties of gas molecules and their motion. KMT helps explain how radio waves are transmitted and why the sky is blue.
5.2: Phase Changes
Read this page, which takes a more in-depth look at the properties of liquids, which were previously introduced. Have you ever wondered why all soap bubbles are round? The concepts discussed here will explain.
Watch these videos, which explain how to calculate the amount of energy associated with both temperature changes and phase changes of a particular substance.
Read this page, and focus on the section pertaining to the unit cell. Some terms related to symmetry and spectroscopy are introduced here, but not covered in detail. More advanced chemistry courses would go into these concepts further.
Read this page, which covers the class of solids that form from ions and the energetics of these compounds.
Read this page, which builds on the concept of the unit cell and describes the packing structures of simple cubic lattices.
- Read this page, which describes the dynamic equilibrium between phases and introduces phase diagrams. There are six different processes by which phases can change from one to another. Some will be familiar to you, such as evaporation or freezing; others might be less familiar, like sublimation and deposition.
Watch these videos to reinforce your understanding of phasediagrams. Although we deal with the three primary states of matter (gases, solids, and liquids) every day, we are often not familiar with their microscopic interactions.
Unit 5 Assessment
Please take this assessment to check your understanding of the materials presented in this unit.
Notes:
- There is no minimum required score to pass this assessment, and your score on this assessment will not factor into your overall course grade.
- This assessment is designed to prepare you for the Final Exam that will determine your course grade. Upon submission of your assessment you will be provided with the correct answers and/or other feedback meant to help in your understanding of the topics being assessed.
- You may attempt this assessment as many times as needed, whenever you would like.