General Chemistry: Matter, Elements, and Compounds

• General chemistry involves studying matter, its properties, and its changes.
• It provides the groundwork needed for other chemistry areas.

Matter

• Matter possesses mass and occupies space.
• The three states of matter are solid, liquid, and gas.
• Solids maintain a consistent shape and volume.
• Liquids maintain a consistent volume but adapt to the shape of their container.
• Gases lack a definite shape or volume and are compressible.
• Plasma is sometimes referred to as the fourth state of matter.

Elements and Compounds

• Elements are substances that cannot be simplified into other substances through chemical processes.
• Elements form the basic components of matter.
• Compounds consist of two or more elements chemically joined in specific ratios.
• Compounds can be broken down into simpler substances or elements through chemical reactions.
• Mixtures are combinations of multiple substances that are physically mixed.
• Mixtures may either be homogenous or heterogeneous.

Atoms and Molecules

• Atoms are the smallest unit of an element with the same chemical attributes.
• Atoms comprise protons, neutrons, and electrons.
• Molecules are two or more atoms chemically bonded.
• Molecules can consist of a single element or multiple.
• Ions are atoms or molecules that have gained or lost electrons, which creates a net electrical charge.
• Cations are ions that carry a positive charge.
• Anions are ions that carry a negative charge.

Chemical Reactions and Equations

• Chemical reactions involve the rearrangement of atoms and molecules.
• Chemical equations use formulas and symbols to represent chemical reactions.
• Reactants are the initial materials combined in a chemical reaction.
• Products are the substances that result from a chemical reaction.
• Chemical equations should be balanced according to the law of conservation of mass.
• Balancing ensures the type and number of atoms are equal on both reaction sides.

Stoichiometry

• Stoichiometry involves the quantitative relationships between reactants and products in chemical reactions.
• The mole is the SI unit defining the amount of a substance.
• Avogadro's number is 6.022 x 10^23, representing the entities in one mole of a substance.
• Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).
• Stoichiometric calculations employ mole ratios from balanced equations to find reactant and product amounts.
• The limiting reactant is the reactant depleted first in a chemical reaction.
• The excess reactant is the reactant present beyond what is needed.
• Theoretical yield is the maximum product amount that can be created.
• Actual yield is the product amount obtained from a chemical reaction.
• Percent yield is actual yield related to theoretical yield.

Solutions

• Solutions are homogeneous mixtures.
• A solute dissolves into a solvent.
• A solvent facilitates the dissolution.
• Concentration measures the amount of solute in solvent or solution.
• Molarity, expressed as M, defines the number of solute moles per liter of solution.
• Dilution is the process of reducing a solution's concentration by adding a solvent.

Acids and Bases

• Acids release protons in solutions.
• Bases accept protons, or release hydroxide ions, when combined with water.
• The pH scale is from 0-14 and measures acidity or basicity.
• On the pH scale, 7 is neutral, values lower than 7 are acidic, and values higher than 7 are alkaline.
• Strong acids and bases fully dissociate in water, whereas weak acids and bases only partly dissociate.
• Acid-base neutralization reactions involve the reaction of an acid with a base to create salt and water.

Gases

• Gases are a state of matter without a fixed shape or volume and can be compressed.
• Gas laws dictate gas behavior and include: Boyle's law, Charles's law and the ideal gas law (PV = nRT).
• Pressure (P) is the force per area unit.
• Volume (V) is the space a gas occupies.
• Temperature (T) reflects the gas molecules' average kinetic energy.
• The ideal gas constant (R) links pressure, volume, temperature, and gas moles.

Thermodynamics

• Thermodynamics studies energy and its changes
• Energy can do work or transfer heat
• The first law of thermodynamics states that energy is always conserved
• Enthalpy (H) measures a system's heat at constant pressure
• Exothermic reactions emit heat and have a negative ΔH
• Endothermic reactions require heat and have a positive ΔH
• Entropy (S) measures a system's disorder
• The second law of thermodynamics the universe's entropy always rises during spontaneous processes
• Gibbs free energy (G) uses enthalpy and entropy to indicate a process's spontaneity
• A negative ΔG signifies a spontaneous process, a positive ΔG indicates a non-spontaneous process, and a ΔG of zero indicates a system at equilibrium.

Chemical Kinetics

• Chemical kinetics studies reaction rates.
• Reaction rates are the concentration change of reactants or products over time.
• Reaction rates depend on temperature, concentration, surface area, and catalysts.
• Catalysts accelerate reactions by reducing activation energy.
• Reaction mechanisms detail elementary reactions in a chemical reaction.

Equilibrium

• Chemical equilibrium occurs when forward and reverse reaction rates equalize.
• At equilibrium, reactant and product concentrations show no net change.
• The equilibrium constant (K) quantitatively shows reactant and product amounts at equilibrium.
• Le Chatelier's principle indicates a system at equilibrium will counteract applied changes in conditions.
• Factors such as temperature, pressure, or reactant/product concentration can cause changes to the reaction in equilibrium.

Redox Reactions

• Redox reactions transfer electrons.
• Oxidation involves losing electrons.
• Reduction involves gaining electrons.
• Oxidizing agents gain and are reduced.
• Reducing agents lose and are oxidized.
• Balancing redox reactions commonly uses the half-reaction method.

Explore general chemistry, the study of matter and its properties. Learn about the three common states of matter: solid, liquid, and gas. Discover the differences between elements and compounds, and how they form the building blocks of matter.