This program traces the story of how humans have always practiced chemistry; how, over time, it developed from a practical discipline into a science. Today, we keep up the chemists' tradition to refine and purify substances. A current, real-life application of the "art of the meticulous" is the refining and purification of pure silicon from a common material—silica sand—for advanced electronics, such as cell phones and solar cells.
This program explores the phases of matter—solids, liquids, and gases—and how particles in a given phase interact with each other. Phase diagrams explain at what temperature and pressure a given substance will be in a solid, liquid, or gas phase. Practical problems, like how to safely store enough hydrogen gas to power an automobile, are solved by understanding the different behaviors of solids, liquids, and gases. Understanding the relationships between temperature, pressure, and volume eventually led to the Ideal Gas Law, which provides the platform for examining the conditions under which matter can form a supercritical fluid. Researchers are investigating underground sequestration of supercritical carbon dioxide to mitigate the environmental impact of burning fossil fuels.
In the early 20th century, identification of the internal parts of the atom (electrons, protons, and neutrons) led to a modern subatomic theory. Meanwhile, the study of atomic spectra—the light given off by atoms at definite wavelengths—led to the Bohr model of the atom, where electrons exist at distinct energy levels and move between these levels by absorbing and emitting discrete quanta of energy. The measurement of atomic spectra has applications in astrophysics as well as forensic chemistry.
For centuries, chemists tried different methods to organize elements around patterns of chemical and physical trends, or regularities, eventually leading to the modern periodic table. Electron configuration is a powerful predictive tool, a simple extension from the periodic table. Physical characteristics, including atomic radius and reactivity, all depend on electron configuration and can be teased from a careful understanding of the periodic table. A living document, the periodic table is continually updated as new manmade heavy elements are discovered in research laboratories.
Molecules can form when atoms bond together by sharing electrons and can be represented by a useful shorthand called Lewis Structures. These visual representations provide information to predict the three-dimensional shapes of molecules using valence shell electron pair repulsion ("VSEPR") theory. Understanding how atoms bond within molecules provides insight into cell replication. Building on this knowledge, the shapes of molecules reveal the effectiveness of important antibiotics such as penicillin, and scientists can manipulate shapes of molecules to help design new cancer-treating drugs.
Stoichiometry gives us the quantitative tools to figure out the relative amounts of reactants and products in chemical reactions. Balancing the number of atoms on each side of the equation, calculating the amount of each reactant, and figuring out which reactant will run out first are all fundamental principles when designing any chemical reaction. These principles are applied when splitting water into hydrogen and oxygen for energy, manufacturing sodium iodide for radiation detectors, and producing common chemicals from renewable resources.
The phrase "chemical reaction" conjures up images of explosions, bubbling gases, flames, and smoke. So many chemical reactions have visible results because energy is being transferred from one form to another—the realm of thermodynamics. Thermodynamics provides rules for predicting the progress of a reaction and for harnessing the energy released. It is key to solving pressing engineering problems, such as making the next generation of cleaner, and more efficient, automobile engines.
The majority of chemical reactions happen in solutions—whether inside an espresso machine or in a human cell. For example, when we breathe, the nitrogen in the air dissolves in our blood. Henry's Law gives us the power to predict, prevent, and treat "the bends"—a life-threatening condition that can happen to SCUBA divers when nitrogen in the blood comes out of solution and forms gas bubbles. Solution chemistry provides tools to measure the concentration of components of solutions, like the CO2 levels in ocean water. Knowing the concentrations of components in solutions can help determine the health of the world.
Light a match and chemical change happens in a one-way process: Reactants are transformed into products. But there are many chemical reactions called "equilibrium reactions" that operate in both directions: with reactants and products always present. The Unit 9 video will show how chemical equilibrium works, the essential role it plays in the function of the human body, and how it is exploited in chemical processes such as ammonia synthesis, a process that provides food for up to half the world's population.
Acids and bases are found all around us, and the currency of acid-base chemistry is the proton, or hydrogen ion. Acid-base chemistry is part of everyday life, from baking and the food we eat to the innumerable reactions that keep the human body alive. Acid-base chemistry is measured on the pH scale—the concentration of hydrogen ions in a solution. Buffers can control pH, whether used in the lab or in the acid-base components of human blood. The role of acids and bases will be shown in food—from the rise of a cake to the making of cheese. In the environment, acid rain plagues industrial portions of the world; the chemical nature of acid rain reactions and the environmental response and impact are part of acid-base chemistry.
Metals allow the transfer of electrons through a process called oxidation-reduction, or "redox," when one species gains electrons while another loses them. Chemists take advantage of this process by using electron transfers to power the batteries in our flashlights, phones, or cars. In biochemistry, trace metals, such as cobalt in Vitamin B12, often drive chemical reactions that are essential for human health. Redox reactions also occur without metals, as is the case when lightening hair color.
From an instantaneous explosion to the slow rusting of iron, the rates at which different chemical reactions proceed can vary tremendously depending on several factors, including temperature and concentration. Sometimes, like with the rotting of food, chemists want to slow down reaction rates. But often, the goal is to speed them up—and one way to do this is to use a catalyst. In this video, we will learn about catalysts and how using them can lead to cheaper, more effective, and more sustainable drug production processes. We will also discover how the rates of some reactions, like nuclear decay, are unchangeable, and how scientists take advantage of this, using PET scans to reveal the presence of disease.
While chemical reactions in gases and liquids are essential to the understanding of chemistry, the chemistry of solid-state materials characterizes most of the interactions we have with matter on a daily basis. Chemists take advantage of the complexity of solids to engineer new materials, including nanoparticles, polymers, and advanced metal alloys. These new materials have many potential applications in sensors, advanced drug delivery systems, and space exploration. Today, modern materials are following a heritage—one that can be traced back to earlier civilizations—in which the properties of solids are manipulated to advance human needs.
