Introduction to Chemistry: Matter, Atoms, and Molecules

• Chemistry is the study of matter, its properties, and how it changes.
• It is a natural science focused on atoms, molecules, and their interactions.

Matter

• Matter possesses mass and occupies space.
• Matter exists as a solid, liquid, gas, and plasma.
• Solids maintain a definite shape and volume.
• Liquids have a definite volume and assume the shape of their container.
• Gases lack definite shape or volume and are compressible.
• Plasma constitutes an ionized gas with substantial energy.

Atoms

• Atoms serve as the fundamental building blocks of matter.
• Atoms consist of protons, neutrons, and electrons.
• Protons are positively charged and reside in the nucleus.
• Neutrons are neutral particles located in the nucleus.
• Electrons are negatively charged and orbit the nucleus.
• The number of protons defines the element.
• Isotopes represent atoms of an element with varying neutron counts.

Molecules

• Molecules arise from the chemical bonding of two or more atoms.
• Chemical bonds are either covalent (sharing electrons) or ionic (transferring electrons).
• Covalent bonds form between nonmetals.
• Ionic bonds form between metals and nonmetals.
• A chemical formula denotes the types and quantities of atoms in a molecule (e.g., H2O).

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms and molecules.
• Reactants are the entities that experience change.
• Products are the entities that are formed.
• Chemical equations symbolize chemical reactions.
• Balancing chemical equations ensures equal atom counts for each element on both sides.
• Stoichiometry addresses quantitative relationships between reactants and products.
• A mole is a unit of amount, equivalent to 6.022 x 10^23 entities (Avogadro's number).

Acids and Bases

• Acids donate protons (H+) or accept electrons.
• Bases accept protons or donate electrons.
• The pH scale quantifies solution acidity or basicity.
• pH values range from 0 to 14.
• A pH < 7 signifies an acidic solution.
• A pH = 7 signifies a neutral solution.
• A pH > 7 signifies a basic solution.
• Strong acids and bases dissociate completely in water.
• Weak acids and bases dissociate partially in water.
• Neutralization is the reaction between an acid and base, generating salt and water.

Organic Chemistry

• Organic chemistry explores carbon-containing compounds.
• Carbon atoms form stable bonds with other carbon atoms and with elements like hydrogen, oxygen, and nitrogen.
• Hydrocarbons exclusively contain carbon and hydrogen.
• Alkanes, alkenes, and alkynes signify hydrocarbons with single, double, and triple bonds, respectively.
• Functional groups constitute specific atomic groupings within molecules that dictate characteristic chemical reactions.
• Common functional groups include alcohols (-OH), carboxylic acids (-COOH), and amines (-NH2).
• Isomers are molecules sharing a molecular formula but differing in structure and properties.

Thermodynamics

• Thermodynamics examines energy and its transformations.
• Energy is the capacity to perform work.
• The first law of thermodynamics states that energy is conserved.
• The second law of thermodynamics states that the entropy of an isolated system tends to increase.
• Enthalpy (H) measures the heat content of a system.
• Entropy (S) measures the disorder or randomness of a system.
• Gibbs free energy (G) measures the spontaneity of a process.
• A reaction is spontaneous (favored) if ΔG < 0.
• A reaction is at equilibrium if ΔG = 0.

Kinetics

• Chemical kinetics studies reaction rates.
• Reaction rate is the change in reactant or product concentration per unit time.
• Factors influencing reaction rates include temperature, concentration, and catalysts.
• Catalysts accelerate reactions without being consumed.
• Activation energy is the minimum energy for a reaction to occur.

Solutions

• A solution is a homogeneous mixture of multiple substances.
• The solvent is the substance present in the greatest amount.
• The solute is the substance present in a lesser amount.
• Concentration denotes the amount of solute in a given amount of solvent or solution.
• Molarity (M) is moles of solute per liter of solution.
• Solubility is the maximum solute that can dissolve in a given amount of solvent at a specific temperature.
• Solubility relies on temperature and pressure.

Redox Reactions

• Redox reactions involve electron transfer between species.
• Oxidation is the loss of electrons.
• Reduction is the gain of electrons.
• Oxidizing agents accept electrons.
• Reducing agents donate electrons.
• Oxidation numbers are assigned to atoms to track electron movement.

Explore the fundamentals of chemistry, including the definition of matter and its various states: solid, liquid, gas, and plasma. Learn about atoms, the basic building blocks of matter, consisting of protons, neutrons, and electrons. Discover how atoms combine to form molecules.