Introduction to Chemistry and Matter

• Chemistry is the study of matter and its properties, as well as how matter changes.

Matter

• Matter is anything that has mass and takes up space.
• It exists in different states, including solid, liquid, gas, and plasma.
• Matter is composed of atoms, which are the smallest units of an element that retain the chemical properties of that element.
• Atoms are made up of protons, neutrons, and electrons.
• Elements are substances that cannot be broken down into simpler substances by chemical means.
• Compounds are substances composed of two or more elements chemically bonded in fixed proportions.
• Mixtures are combinations of substances that are physically mixed but not chemically combined, and they can be homogeneous or heterogeneous.

Properties of Matter

• Physical properties are those that can be observed or measured without changing the substance's composition (e.g., color, density, melting point).
• Chemical properties describe how a substance reacts with other substances or changes its composition (e.g., flammability, reactivity with acids).
• Intensive properties do not depend on the amount of substance (e.g., temperature, pressure, density).
• Extensive properties depend on the amount of substance (e.g., mass, volume).

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms and molecules to form new substances.
• Reactants are the starting materials in a chemical reaction.
• Products are the substances formed as a result of a chemical reaction.
• Chemical equations represent chemical reactions using chemical formulas and symbols.
• Balancing chemical equations ensures that the number of atoms of each element is the same on both sides of the equation, following the law of conservation of mass.
• Types of chemical reactions include synthesis, decomposition, single displacement, double displacement, and combustion.

Stoichiometry

• Stoichiometry is the quantitative study of the relationships between reactants and products in chemical reactions.
• The mole is the SI unit for the amount of substance, defined as the number of carbon atoms in exactly 12 grams of carbon-12.
• Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).
• Stoichiometric calculations involve using mole ratios from balanced chemical equations to determine the amounts of reactants and products in a reaction.
• Limiting reactant is the reactant that is completely consumed in a reaction, determining the maximum amount of product that can be formed.
• Percent yield is the ratio of the actual yield (amount of product obtained) to the theoretical yield (amount of product calculated from stoichiometry), expressed as a percentage.

Acids and Bases

• Acids are substances that donate protons (H+) or accept electrons, and they have a pH less than 7.
• Bases are substances that accept protons or donate electrons, and they have a pH greater than 7.
• pH is a measure of the acidity or basicity of a solution, defined as the negative logarithm of the hydrogen ion concentration ([H+]).
• Strong acids and bases completely dissociate in water, while weak acids and bases only partially dissociate.
• Neutralization is the reaction between an acid and a base, which produces a salt and water.
• Titration is a technique used to determine the concentration of an acid or base by reacting it with a solution of known concentration (a standard solution).

Chemical Bonding

• Chemical bonds are the attractive forces that hold atoms together in molecules and compounds.
• Ionic bonds are formed by the transfer of electrons between atoms, resulting in the formation of ions (charged particles).
• Covalent bonds are formed by the sharing of electrons between atoms.
• Metallic bonds are found in metals, where electrons are delocalized and shared among many atoms.
• Bond polarity describes the distribution of electron density in a bond, with polar bonds having an unequal sharing of electrons and nonpolar bonds having an equal sharing of electrons.
• Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond.

States of Matter

• Solids have a fixed shape and volume, with strong intermolecular forces holding the particles in a fixed arrangement.
• Liquids have a fixed volume but take the shape of their container, with weaker intermolecular forces allowing the particles to move more freely.
• Gases have no fixed shape or volume and are highly compressible, with very weak intermolecular forces allowing the particles to move independently.
• Phase changes involve the transition between different states of matter, such as melting, freezing, boiling, condensation, sublimation, and deposition.
• Intermolecular forces (e.g., hydrogen bonding, dipole-dipole forces, London dispersion forces) affect the physical properties of substances, such as boiling point and melting point.

Chemical Kinetics

• Chemical kinetics is the study of reaction rates and the factors that affect them.
• Reaction rate is the change in concentration of reactants or products per unit time.
• Factors affecting reaction rates include temperature, concentration, surface area, and catalysts.
• Catalysts are substances that speed up a reaction without being consumed in the reaction.
• Rate laws express the relationship between reaction rate and the concentrations of reactants.
• Activation energy is the minimum energy required for a reaction to occur.

Chemical Equilibrium

• Chemical equilibrium is the state in which the rates of the forward and reverse reactions are equal, and the net change in concentrations of reactants and products is zero.
• Equilibrium constant (K) is a measure of the relative amounts of reactants and products at equilibrium.
• Le Chatelier's principle states that if a change of condition (e.g., temperature, pressure, concentration) is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.

Organic Chemistry

• Organic chemistry is the study of carbon-containing compounds.
• Carbon atoms can form stable chains and rings, allowing for a vast diversity of organic molecules.
• Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules.
• Common functional groups include alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, and amines.
• Hydrocarbons are organic compounds containing only carbon and hydrogen atoms, and they can be saturated (alkanes) or unsaturated (alkenes and alkynes).
• Isomers are molecules with the same molecular formula but different structural arrangements.

Thermodynamics

• Thermodynamics is the study of energy and its transformations.
• Energy is the capacity to do work or transfer heat.
• The first law of thermodynamics states that energy is conserved; it cannot be created or destroyed, but it can be converted from one form to another.
• Enthalpy (H) is a measure of the heat content of a system at constant pressure.
• Entropy (S) is a measure of the disorder or randomness of a system.
• Gibbs free energy (G) is a measure of the spontaneity of a process, combining enthalpy and entropy.
• Exothermic reactions release heat (ΔH < 0), while endothermic reactions absorb heat (ΔH > 0).