Avogadro's suggestion that a volume of any gas, under equal temperature and pressure, contains the same number of particles, led to an understanding of the relationship between temperature and pressure and to the Ideal Gas Law. Today, a fourth state of matter, the supercritical fluid, may possibly help mitigate the impact of burning fossil fuels by storing carbon dioxide as a supercritical fluid within the Earth.
Researchers are developing methods to pack hydrogen gas into carbon nanostructures for use as fuel in hydrogen-powered vehicles. 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. Before scientists knew about the subcomponents of atoms, they organized elements based on physical and chemical properties. Dmitri Mendeleev developed an early Periodic Table of the 63 known elements, leaving gaps for the discovery of new elements to come. His table was enhanced by Henry Moseley who enabled today's ordering of the elements, based on the number of protons.
Scientists at Lawrence Livermore Labs have synthesized new elements up to atomic number These new elements further our understanding of the mysteries of the atom and also have useful applications in forensic science.
When molecules form, the elements bond to one other by sharing or exchanging electrons. The program shows how this simple, but powerful, bonding mechanism — when combined with electron pair repulsion — leads to the 3-dimensional structure of molecules. Using these principles, scientists can build molecules that disrupt the chemical processes of cancer cell replication. To manipulate chemical reactions on a large scale, scientists use stoichiometry to quantify those reactions and make sure that there are just the right amount of reactants and products.
Without it, reactions can be incomplete, with expensive materials wasted and harmful byproducts created. Using stoichiometry, scientists are creating chemicals that take the place of petroleum in fabricating sustainable materials.
By first looking at work and heat, the course adds another dimension: the energetics of chemical reactions. This study of thermodynamics can lead to predicting how chemical reactions will proceed or how much energy is required or released during the reactions. Practical applications of bond enthalpies, calorimetry, and other measurements of the energy in chemical reactions is helping scientists optimize the use of crop waste for biofuels and build more efficient automobile engines.
Solutions are uniform mixtures of molecules in which any of the phases of matter can be dissolved in another phase. Whether solids, liquids, or gases, solution chemistry is important because most chemical reactions, whether in the laboratory or in nature, take place in solutions. In particular, solutions with water as the solvent — aqueous solutions — are the core of all biology.
Extending the particle model of matter to solutions enables chemists to predict what will happen to a deep-sea diver who breathes different mixtures of gases, or to the life forms in the ocean as CO2 levels rise in the atmosphere. Some chemical reactions, like metal rusting, happen spontaneously.
Others require external energy in order to occur. Expanding upon the basic thermodynamics of enthalpy from Unit 7, disorder entropy and Gibbs free energy are key to understanding what makes chemical reactions proceed thermodynamically.
When the thermodynamics of a reaction prevent it from reaching completion, both products and reactants are always present it is called equilibrium. When equilibrium reactions are disrupted, such as the binding of oxygen by hemoglobin, as in carbon monoxide poisoning, it can be life threatening.
Conversely, controlling an equilibrium reaction is important in chemical manufacturing, like in the synthesis of ammonia. Acids and bases are important to many chemical processes: maintaining a stable internal environment in the human body, baking a delicious cake, or determining whether a lake can support aquatic life.
For chemists, the number of those acidic hydrogen ions can be quantified by using the pH scale. The reactions of acids and bases, which can be monitored with indicators, can range from corrosive behavior to neutralizations that leave no acids or bases behind. To understand the controlling of pH of solutions, buffers are discussed in the laboratory and in the chemistry of the bloodstream. Electrochemistry is the study of chemical reactions in which the reactants transfer electrons from one compound to another.
This group lies in the s-block of the periodic table, as all alkali metals have their outermost electron in an s-orbital. The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting similar properties.
For instance, when moving down the table, all known alkali metals show:. In general, their densities increase when moving down the table, with the exception of potassium, which is less dense than sodium. Alkali metals react violently with water, halogens, and acids. The reactions release surprising amounts of heat and light. In a chemical equation, alkali metals are represented with an M. Here are some sample reaction equations:. All the discovered alkali metals occur in nature.
Experiments have been conducted to attempt the synthesis of ununennium Uue , which is likely to be the next member of the group if the attempt is successful.
It is predicted that the next alkali metal after ununennium would be unhexpentium Uhp , an element that has not yet received even attempts at synthesis due to its extremely high atomic number.
Most alkali metals have many different applications. Two of the most well-known applications of the pure elements are rubidium and cesium atomic clocks, of which cesium atomic clocks are the most accurate representation of time known as of A common application of the compounds of sodium is the sodium-vapor lamp, which emits very efficient light.
Table salt, or sodium chloride, on the other hand, has been used since antiquity.
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